Dynamics Magazine 301

issue 3.01

integrate. automate. innovate.

Features

ING Renault F1 Team Formula One Aerodynamics

SUBMARINE Maneuvering Simulations

LIFEBOAT LAUNCHING Accurately Simulated

HOT STUFF Vehicle Thermal Management

contents Introduction 03 Integrate. Automate. Innovate.

Introduction by Bill Clark 05

Breaking News • STAR-CCM+ V4.02 Release • Office News

• STAR-CD 4.08 Release • No Engineer Left Behind

Aerospace 07 Propulsive Wing

Aerial Utility Vehicle Development

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11

15

19

23

25

31

37

39

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Transportation 11 ING Renault F1 Team Takes The Lead With STAR-CCM+

Formula One Aerodynamics 15

Formula for Success Using STAR-CCM+ to design a 2009 Formula SAE race car

19 Track Car Aerodynamics

Analyzing the effect of aerodynamic enhancements on a small hatchback 22 The Seven Benefits

Improve productivity and cost effectiveness through CFD 23

Fuel Cells Modeling the future of Power Generation

25

Hot Stuff Vehicle Thermal Management in STAR-CCM+

29 Design for Six Sigma

Optimization of Engine Intake Manifold Design 31 Simulate to Understand

CFD helps to understand the history and evolution of racing techniques Marine 34 Aker Yards Marine Case Studies:

Validating Hull Performance using CFD

Improving Cryogenic Analyses with CFD

Dynamic Positioning Studied with CFD 37 Submarine Maneuvering Simulations

Accurately predict how a submarine’s motion is driven by hydrodynamic forces 39 Simulation of Lifeboat Launching

Under Storm Conditions 43 Challenges and Solutions

Hydrodynamic Aspects of Containership Propulsion Turbomachinery 41 Eliminating Heat Stress Failures

Industrial Turbines Regulars 49 Competition: Calendar 2009 Winners 51 Dr Mesh 53 Training 54 Global Events

RECYCLED PAPER. VEGETABLE INKS.

EDITORIAL Dynamics welcomes editorial from all users of CD-adapco software or services.

To submit an article: Email editorial@uk.cd-adapco.com Telephone: +44 (0)20 7471 6200 Editor Sub-editor Features Editor Associate Editor Art Direction & Design Advertising Sales Multimedia Director US Events European Events

Stephen Ferguson - stephen.ferguson@uk.cd-adapco.com Joel Davison - joel@uk.cd-adapco.com Dejan Matic - dan.matic@us.cd-adapco.com Lauren Wright - lauren.wright@us.cd-adapco.com Brandon Botha - brandon.botha@uk.cd-adapco.com Geri Jackman - geri@uk.cd-adapco.com Mark Adlington - marka@uk.cd-adapco.com Tara Firenze - tara.firenze@us.cd-adapco.com Marianne Müller - marianne.mueller@de.cd-adapco.com

Subscriptions Dynamics is published approximately three times a year, and distributed internationally.

To subscribe or unsubscribe, please email info@uk.cd-adapco.com Telephone +44 (0)207 471 6200 Media Kit available online at: http://www.cd-adapco.com/press_room Cover Image: Joseph Kummer - Propulsive Wing

Global offices CD-adapco Americas

Europe

Asia-Pacific

United States Headquarters CD-adapco • New York office 60 Broadhollow Road Melville, NY 11747, USA Tel.: (+1) 631 549 2300 info@us.cd-adapco.com www.cd-adapco.com Atlanta GA Austin TX Cincinnati OH Detroit MI Houston TX Lebanon NH Los Angeles CA Seattle WA State College PA Tulsa OK info@us.cd-adapco.com For S. America - please contact Melville Office

United Kingdom Headquarters CD-adapco • London office 200 Shepherds Bush Road London, W6 7NL, UK Tel.: (+44) 20 7471 6200 info@uk.cd-adapco.com www.cd-adapco.com Aberdeen info@uk.cd-adapco.com France: Lyon, Paris info@fr.cd-adapco.com Germany: Nürnberg info@de.cd-adapco.com Italy: Rome, Turin info@it.cd-adapco.com Norway: Oslo info@no.cd-adapco.com

India: CD-adapco India Bangalore info@in.cd-adapco.com Japan: CDaEs Tokyo info@jp.cd-adapco.com Korea: CD-adapco Korea Seoul info@cdak.co.kr Singapore: CD-adapco SEAsia Singapore info@sg.cd-adapco.com

New Zealand Matrix Applied Computing Ltd. sales@matrix.co.nz Russia SAROV info@saec.ru South Africa Aerotherm Computational Dynamics martin@aerothermcd.co.za Turkey A-Ztech Ltd info@a-ztech.com.tr

China CDAJ China Beijing • Shanghai info@cdaj-china.com Japan CDAJ Japan Yokohama • Kobe info@cdaj.co.jp

Resellers Australia Veta Pty info@veta.com.au Brazil Multicorpos multicorpos@multicorpos.com.br Greece ENEFEL enefel@enefel.gr Israel ADCOM info@adcomsim.co.il

..::INTRODUCTION Integrate. Automate. Innovate.

On it’s simplest level automation provides a stress free path from geometry import to engineering simulation results.

Integrate. Automate. Innovate.

Introduction by Bill Clark In the midst of constant media reminders about how tough times are, it’s difficult not to be at least a little gloomy about the prospects for the engineering business as a whole. This issue of Dynamics is designed to provide an antidote to the doom and gloom showing that, not only is the CAE business as buoyant as ever, but that simulation is becoming even more pervasive, being used at every stage of the engineering process, and penetrating all levels of industry.

This magazine contains stories that demonstrate how CFD is being used for everything from student motorsport design to the historical analysis of long forgotten race cars, in each case demonstrating that serious engineering analysis can be performed using very limited resources.

Just a few years ago this would have been unthinkable. Serious vehicle aerodynamic simulation was the sole preserve of race-car manufacturers and OEMs, each of whom would employ large teams of dedicated specialists working a cluster of machines around the clock to churn out timely engineering data capable of positively influencing the vehicle design.

The innovation that is driving this trend is “automation”. At its simplest level automation provides a stress free path from geometry import to engineering simulation results. For generations of engineers, such as myself, who built careers and reputations on mastering the “blood, sweat and tears” approach to CFD (manually generating meshes for complex industrial geometries), this can seem a little disconcerting, however automation has good news here too.

The overriding goal of automation is to free engineers from the repetitive and mundane tasks associated with preparing and running simulations, allowing them to spend more time analyzing engineering results and generating a constant stream of information to guide the design process, ultimately resulting in more innovative, better engineered, products. Rather than focusing on just a few design points, engineers have the opportunity, for the first time, to simulate entire design spaces.

i EMAIL: bill.clark@us.cd-adapco.com

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A good example of this is our cover story from Propulsive Wing LLC (pg 07) in which STAR-CCM+ was used to map the complex relationship between propulsion system settings and the aircraft stability - creating a stable aircraft design before the first prototype had been constructed. A thumb through these pages, or a visit to one of our upcoming webinars, seminars or STAR conferences should help to convince you that automation really is the future of Computer Aided Engineering, and that no company is better placed to provide you with the necessary tools than CD-adapco.

Finally, I’d like to draw your attention to the “No Engineer Left Behind” program, which offers free training and STAR-CCM+ licenses to Engineers that have recently lost their job as a result of the economic climate. If you know anyone in this position, please encourage them to participate in the program.

Bill Clark Senior Vice President, Worldwide Sales and Support CD-adapco

..::INTRODUCTION Breaking News CD-adapco opens new SEAsia Office in Singapore Stephen Ferguson We are proud to announce our further expansion into the Asian markets with the opening of a new office in Singapore. The decision to launch the South East Asian operations in Singapore is a reflection not only of CD-adapco’s continued commitment to the Energy and Oil and Gas industries, but of an increased commitment to the Asian market in general.

Singapore has a 70% worldwide market share of both the FPSO conversions and the jack-up rigs as well as a strong refining industry, and has therefore long been regarded South East Asia’s Oil and Gas hub. The level of oil and gas related activities in

neighboring countries, Indonesia and Malaysia, further contribute to building up a strong regional oil and gas centre and in general an energy hub as a whole. The Energy Information Administration predicts that the worldwide demand for energy will increase by over 70% by 2030, with the majority of that growth in demand coming from Asia growth (between 2000-2005, demand growth in Asia was 33% vs. 2% in the USA as reported by BP Statistical Review of World Energy).

i MORE INFORMATION http://www.cd-adapco.com/press_room/2009/02-16-singapore.html

STAR-CD V4.08: Reliable and Accurate Multiphysics Simulation Joel Davison STAR-CD V4.08 is the fifth major release of STAR-CD V4 and the first software release of 2009.

As with previous releases, STAR-CD V4.08 embodies over 20 years of development experience and is a reliable and highly accurate tool for the simulation of advanced physics phenomena. As well as introducing new models, we have invested significantly in enhancing and tuning the existing capabilities to increase both their speed and robustness.

Notable among the new features is an enhanced multiphase capability that removes the limit of two phases for both VOF and Eulerian simulations, allowing the user to effectively specify any number

of discrete phases in their calculations. For LES type simulations, the new “Synthetic Eddy Methodology” simplifies the prescription of inflow boundary condition. Several new combustion models are also included.

The new “Time Parallel” capability extends the limits of efficient parallel processor utilization, by allowing users to parallelize their simulations in time as well as space: an approach that has yielded significant benefits for simulations such as those involving very long pipelines. Parallel performance is also improved for es-ice simulation.

STAR-CD V4.08 also brings STAR-CD users up-to-date with the latest developments in automatic meshing technology. A direct interface between STAR-CD and ABAQUS further simplifies the

simulation of problems involving Fluid Structure Interaction without the need for third party cross-code communication software.

To download STAR-CD V4.08 please visit our User Services Site, or contact your local support office.

We also strongly recommend you to take the time to read the Release Notes that are provided with the installation package. The Release Notes will provide you with an exhaustive overview of the new features and improvements as well as all of the enhancement requests that have been implemented in this release.

i Try STAR-CD V4.08 today http://www.cd-adapco.com/press_room/2009/01_14_starcd408.html

CD-adapco opens new offices in Oslo and Aberdeen

CD-adapco recently announced openings of offices in Aberdeen and Oslo, bringing the number of locations in Europe to eight. These new offices demonstrate CD-adapco’s commitment to satisfying the increasing demand for flow thermal and stress software and services in the Oil and Gas industry, and to the Energy Sector as a whole.

“Numerical simulation has a key role to play in delivering sustainable future supplies of energy, no matter what their source,” says Bill Clark, CD-adapco’s Senior VP of Operations. “The recent opening of new offices in Houston, Singapore, Aberdeen and Oslo shows that this organization is fully committed to delivering simulation technology

Stephen Ferguson

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i MORE INFORMATION http://www.cd-adapco.com/press_room

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to the Oil and Gas industry.”

“The new offices give us the opportunity to expand the talented array of people that serve the Scottish and Norwegian markets and the Oil and Gas Industry as a whole,” says CD-adapco President and co-founder Steve MacDonald. “The offices will provide state of the art computing facilities and dedicated customer areas for training and technology transfer. We have always prided ourselves on the quality of our people - becoming a CD-adapco customer means more than purchasing world-class software or services; it opens the door to an unrivalled wealth of engineering expertise.”

..::INTRODUCTION Breaking News

STAR-CCM+ V4: Integrate, Automate, Innovate.

Stephen Ferguson STAR-CCM+ V4 is now available from the User Services Site. In the six years since its first release, STAR-CCM+ has evolved into more than just a CFD code, and is now an integrated platform for powerful multi-disciplinary simulation, including: combustion; multiphase flow; heat transfer through solids and fluids; dynamic fluid body interaction; and solid stress: all from within a single environment.

As with each previous release, STAR-CCM+ V4 includes new physical models, such as the introduction of erosion modeling, improved combustion models as well as the capability to simulate melting and solidification. However, according to Jean-Claude Ercolanelli, CD-adapco’s Vice President Product Management, the new version delivers much more in terms of productivity and collaboration enhancements: ”To play an effective role in a modern integrated engineering environment, simulation demands a tight collaboration among engineers and designers from a wide range of backgrounds and engineering disciplines. STAR-CCM+ V4 introduces new tools that facilitate the sharing of CAD data and engineering simulation, driving innovation through increased levels of integration and automation.”

Integrate STAR-CCM+ V4 provides a free stand-alone results viewer called STAR-View+, that facilitates collaboration between engineering teams by giving everyone access to interactive visualization of the computed results: “Understanding someone else’s simulation displays is never an easy task,” says Ercolanelli. “Industrial CAE results are inherently three-dimensional; in order to properly understand a flow, thermal and stress solution you need to explore it. STAR-View+ is a new utility for STAR-CCM+ that makes the viewing of CAE results more interactive and moreover is accessible to everyone regardless of whether they hold a STAR-CCM+ license or not.”

STAR-CCM+ V4 allows users to distribute post-processed simulation results as “scene files” containing a three-dimensional representation of the

stored CAE plot. When viewed using STAR-View+, scene files allow the viewer to zoom, pan and rotate the stored model and post-processing data, as if the model were in STAR-CCM+. Now anyone, whether a STAR-CCM+ user or not, can have the luxury of fully exploring the solution.

STAR-View+ is free to distribute, requires no license, which means that you can simply attach it to an email with a selection of scene files.

To download and share STAR-View+, along with some example scene files, please visit: www.cd-adapco.com/starviewplus

Automate “Automation is the central tenet of the STAR-CCM+ philosophy,” says Ercolanelli.

“Rather than restricting users to the simulation of a few design points, STAR-CCM+ is specifically designed to allow engineers to simulate the entire design space – spawning multiple design iterations from a single simulation scenario. The release of STAR-CCM+ V4 sees the introduction of a new ‘parts structure’ within the user interface, closing the gap between CAD design and CAE simulation. As CAD data is imported the hierarchy of the assembly is reproduced allowing users the ability to duplicate, replace, repair, transform and export individual components from the tree, manually within the STAR-CCM+ environment, or automatically using simple macros.”

CAD part-names and meta-data are also preserved in the hierarchy, meaning that the simulation remains linked to the original CAD model. Once an initial simulation has been prepared, meshing and physics data are stored in a template, so that any changes to the CAD model can be reflected in the simulation results with little or no effort from the user.

For complex assemblies of parts, STAR-CCM+ V4 can also automatically identify the contact regions between adjacent parts and define a boundary condition and interfaces between them - a feature that considerably eases the process of setting up conjugate heat transfer and thermal stress problems.

To see a video demonstrating the new parts functionality in action, please visit: www.cd-adapo.com/partsdemo

Innovate “The overall benefit of increased automation is that engineers get to spend less time manually preparing simulations and more time analyzing engineering data,” says Ercolanelli. “Increased levels of collaboration mean that this information can more easily be disseminated to the entire engineering organization; breaking down barriers between the different disciplines that contribute to the engineering design of a new product. A constant stream of more complete engineering information flowing through an organization can only lead to better engineered, more innovative products which are better suited to the needs of an increasingly competitive global marketplace.”

To see how STAR-CCM+ drives engineering innovation, please visit our website, register for one of our conferences or subscribe to our customer magazine.

i MORE INFORMATION http://www.cd-adapco.com/products/STAR-CCM_plus

No Engineer Left Behind ‘No Engineer Left Behind’ is an exciting new program from CD-adapco that offers free training and software, aimed at improving the skill and marketability of recently unemployed or displaced engineers.

Qualifying engineers are invited to attend free training courses at any CD-adapco training facility worldwide.

The training is focused on the practical application of engineering simulation software to “real world” industrial problems. The skills developed can easily be applied in a wide range of industries, including: Aerospace and Defense, Automotive, Biomedical, Buildings, Chemical, Environmental, Marine, Oil and Gas, Power Generation, and Turbomachinery.

After successful completion of the training course, attendees will take home a CD-adapco certificate of competence, and a free, 6 month software license of CD-adapco’s world leading CFD code, STAR-CCM+.

Having access to the code will allow attendees to practice and hone the learned skills which are a global standard for CAE simulation. This opportunity is well over $25,000 USD of in-kind value.

i MORE INFORMATION www.cd-adapco.com/training/no_engineer_left_behind/

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..::FEATURE ARTICLE Aerospace

p ABOVE Propulsive Wing is the First Autonomous Aerial Utility Vehicle (AAUV).

Propulsive wing Aerial Utility Vehicle Development Joseph Kummer, Propulsive Wing.

For over a century mankind has devoted substantial resources toward achieving and improving flight. With the yearly threat of major wildfires and the ongoing conflicts in the Middle East as its primary focus, Propulsive Wing, LLC is developing unmanned aerial vehicle solutions for both domestic fire fighting suppor t and military applications, covering a wide range of missions.

The Propulsive Wing is a completely new class of aircraft based on the integration of a cross-flow fan into the trailing edge of an airplane wing. The project began at Syracuse University with funding from NASA Glenn Research Center, and the technology is currently patent pending. Propulsive Wing LLC was founded to continue development and commercialize the platform as an unmanned airplane. Propulsive Wing is partnering with Elbridge, New York based engineering firm Allred & Associates, Inc. to accelerate this process.

With its unique design, for a given wingspan, Propulsive Wings are able to carry up to 3 times the payload weight and 10 times the internal payload volume

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of conventional systems. For this reason, the company calls its aircraft an aerial utility vehicle, or AUV for short. Propulsive Wing AUVs require shorter runways for take-off and landing (due to their extremely high lifting capability), generate low noise, and offer a high degree of user safety due to the elimination of external rotating propellers. This platform is applicable to many aircraft sizes ranging from small to large, unmanned and manned military, experimental, private and commercial passenger and cargo planes.

CFD was used throughout the design process to drive both aerodynamic and manufacturing decisions. For the current PW-4 prototype, which is currently

..::FEATURE ARTICLE Aerospace

p ABOVE Streamlines over the Propulsive Wing AAUV at a high angle of attack.

v Propulsive Wing, LLC was formed in 2006 to commercialize a newly-developed high-lift, high-payload flying wing platform. Instead of external propellers, the design utilizes partially-embedded cross-flow fans for thrust and boundary-layer control. Based on 6 years of research and development, the aircraft is readily scalable and reconfigurable to meet specific mission requirements.

PW-4 prototype coming in for landing Construction of the PW-4 prototype is complete, and the model is now undergoing a flight test program. The vehicle has a wingspan of 7 feet, an empty weight of 24 pounds, and has an estimated payload capacity of over 30 additional pounds.

Initial phases of the flight test program, which explored pitch stability and control and lateral stability and control, have now been completed, and we have verified a stable platform.

The current testing phases involve expanding the flight envelope, and will ultimately involve exploring higher load carrying capabilities.

Over the next month, Propulsive Wing will begin releasing videos of the plane, which will be downloadable from: http://www.propulsivewing.com

undergoing flight-testing, the entire airframe was designed in CAD and modeled using STAR-CCM+ before fabrication even began. The ability of STAR-CCM+ to rapidly import a CAD model and create a new computational mesh allowed for multiple design iterations to be completed within a very short timescale.

In additon to complete aircradt simulations of the PW-4 prototype, CFD was also extensively used to simulate sub-systems. In the design of the cross-flow fan propulsion system, simulation results were used to optimize the blade and housing geometry. Using CFD, Propulsive Wing designed a custom carbon-fiber cross-flow fan with excellent mechanical and aerodynamic performance.

At the next level, simulations were performed to investigate the integration of the cross-flow fan within a propulsive airfoil, these studies looked at the effect of propulsive airfoil design parameters, for example fan speed and sizing, duct inlet and outlet locations, and exhaust angle, on lift, drag, and pitching moment. Also, power requirements in various configurations were calculated.

Full 3D unsteady simulations investigated the performance of the entire airplane. Understanding pitch stability characteristics and creation of a stable aircraft was a major technical hurdle. The Propulsive Wing configuration inherently involves complex coupling between the propulsion system and the wing pressure

distribution, and can result in significant variations in pitching moment. For example, if fan speed is increased, this in turn increases the flow rate, the result is not only higher thrust, but, depending on the exhaust angle, changes the pitch-up or pitch-down tendency of the airplane. Simultaneously, however, the fan also produces greater suction at the air inlet, which alters the pressure distribution on the wing surface, while creating a nose-up reaction due to the direction of rotation. Using STAR-CCM+, Propulsive Wing was able to successfully understand these relationships and create a stable flying aircraft.

The Propulsive Wing fits several niche applications where there currently is no solution. One is large payload, short duration sensor deployment for the military. Also, as the platform scales up, the large cargo and short takeoff and landing capabilities lend the AUV to missions where food, water, or other supplies need to be transported to remote or high altitude locations, both for military, as well as civilian emergency relief.

In addition to military use, one of the primary missions at Propulsive Wing is to develop the aircraft into a frontline component in the suppression of wildfires, which endanger people, wildlife, and agriculture. Annually the US Government spends over $1 billion fighting wildfires, which destroy about 8 million acres. g

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..::FEATURE ARTICLE Aerospace

p ABOVE Pressure contours and polyhedral mesh detail

Furthermore, due to unfavorable weather trends and other factors, forest fires have been growing in number, getting larger, and gaining in intensity.

The goal is to supplement the use of large tanker-sized aircraft with swarms of smaller unmanned drones that will each drop up to 200 pounds of water or fire-retardant chemicals. The short-field capability, compact size, and large cargo-carrying ability of the Propulsive Wing units, will allow rapid deployment from remote areas to help extinguish the thousands of small wildfires reported each year before they grow larger and become a threat to people and property.

The US Forest Service estimates that up to 80% of the total resources expended each year are allocated to the small number of large fires. The goal, then, must be to put out all of the small fires before they become large, thus permitting the Forest Service the time and energy to focus more on controlled burns and forest management to help prevent future fires. Propulsive Wing envisions hundreds of cross-flow fan AUV systems based strategically around the West

and Mid-West regions of the United States fighting wildfires on a 24/7 basis at a fraction the cost, as well as a fraction the risk to the pilots operating the small contract general aviation aircraft used for the same purpose. Such a system will improve the world’s ability to combat forest fires by an order of magnitude. < q BELOW Pressure contours on the AAUV

q BELOW Closeup of the polyhedral mesh around the cross flow fan

q BELOW Cross section of the AAUV ‘s wing

i MORE INFORMATION ON propulsive wing http://www.propulsivewing.com/

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..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Automotive

STAR-CCM+: Insight for Design STAR-CCM+ is an engineering process oriented Computational Fluid Dynamics tool that delivers the latest CFD technology in a single integrated environment, offering a seamless CFD solution.

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Productivity

3

Accuracy

3

Flexibility

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Expertise

What do you expect from your Engineering Simulation Software?

For more information: info@uk.cd-adapco.com

www.cd-adapco.com

..::FEATURE ARTICLE Automotive

RENAULT F1 R29 SPECIFICATIONS Chassis

Front suspension

Rear suspension

Transmission

Moulded carbon fibre and aluminium honeycomb

Carbon fibre top and bottom wishbones operate

Carbon fibre top and bottom wishbones operat-

Seven-speed semi-automatic carbontitanium

composite monocoque, manufactured by the

an inboard rocker via a pushrod system. This

ing angled torsion bars and transverse-mounted

gearbox with reverse gear. “Quickshift” system in

Renault F1 Team and designed for maximum

is connected to a torsion bar and damper

damper units mounted on the top of the gearbox

operation to maximise speed of gearshifts.

strength with minimum weight. RS27 V8 engine

units which are mounted inside the front of

casing. MMC aluminium uprights and machined

installed as a fully-stressed member.

the monocoque. MMC aluminium uprights and

magnesium wheels.

machined magnesium wheels.

Fuel system Kevlar-reinforced rubber fuel cell by ATL.

❐ FACTS

Formula 1 is the world largest annual spor ting event with over one billion cumulative viewers in 184 countries watching races across four continents. In the world of speed where fractions of second determine the difference between the first and last, the competition takes place not only at the race track but in the factory as well.

Branded with the name that por trays the vision of racing excellence, Formula 1 became the leading arena for development and testing of advanced automotive technologies.

Weighing just 605 kilograms in race trim, propelled by an engine that delivers in excess of 800 horsepower, a Formula 1 car is regularly subjected to braking and cornering forces in excess of 5g. The maximum speed depends on aerodynamic setup, which changes from circuit to circuit, but is usually around 340 kph. At that speed, the geometry of the car produces downforce of around two tons. This invisible force pushes the car into the ground, increasing traction and allowing the car to maintain higher cornering speeds and generate greater braking force. Since both lift (in this case negative lift) and drag are functions of velocity squared, the ability to deliver an efficient aerodynamic package on raceday is a critical ingredient in reducing individual lap times by the fractions of a second that

combined are the difference between winning and losing the race. With engine development now frozen and only one tyre manufacturer supplying the whole grid, the aerodynamic package has become a single most important component of race car performance.

The development of a car’s aerodynamic package typically relies on an extensive wind tunnel programme, conducted in parallel with, and to some extent driven by, an even more extensive Computational Fluid Dynamics (CFD) programme. In this mode CFD is largely used as a coarse filter, examining many possible design variants, from which only the best will be tested in the wind-tunnel, CFD also plays a valuable role in simulating physics that can not be adequately handled by the wind-tunnel, for example where thermal effects

The first thing that separates them from the competition is STAR-CCM+, its a state of the art CFD code and since we introduced it about a year ago we have managed to double our throughput in terms of simulations, so it was a massive step forward.

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..::FEATURE ARTICLE Automotive

ING Renault F1 Team Takes The Lead With STAR-CCM+ Dejan Matic, CD-adapco.

Images: Courtesy ING Renault F1 Team

Car dimensions and weight

KERS

Electrical

Cockpit

Motor generator unit driving into front of engine

MES-Microsoft Standard Electronic Control Unit.

Removable driver’s seat made of anatomically

Front track 1450 mm

with batteries as an energy store.

Magnetti-Marelli KERS control unit.

formed carbon composite, with six-point harness

Rear track 1400 mm

seat belt. Steering wheel integrates gear change

Overall length 4800 mm

Cooling system

Braking system

and clutch paddles, front flap adjuster and KERS

Overall height 950 mm

Separate oil and water radiators located in the

Carbon discs and pads (Hitco); calipers and

energy release controls.

Overall width 1800 mm

car’s sidepods and cooled using airflow from the

mastercylinders by AP Racing.

Overall weight 605 kg (driver, cameras & ballast)

car’s forward motion

are important, or where multiple cars interact with one and other (such as the simulation of a passing manaouver). It is also used to explain, and visualize flow mechanisms observed during physical testing, helping optimize any new design modifications so that any potential benefit is maximized. The FIA’s (Federation Internationale de l’Automobile) current focus on reduction of the costs of race car development by limiting time in wind tunnels will certainly increase the importance of, and reliance on, CFD technology.

After several months of in-depth reflection by ING Renault F1’s aerodynamics group, a decision was made to invest in a virtual wind tunnel instead of a physical one: “The decision to head towards a wind tunnel in a computer rather than constructing expensive second wind tunnel is down to the teams strategic approach”, says Bob Bell, ING Renault F1 team Technical Director. “It was a fairly clear cut decision for us based on first, and foremost, technical belief that was the way of the future and it was also based on some pragmatic commercial judgment. This facility has cost us less than an equivalent wind tunnel capacity would be and it’s also a facility that is of interest to potential partners and sponsors.”

The new supercomputer, which was set to work in November 2008, provides the ING Renault F1 team with a five-fold increase in computing capacity, allowing the team to push the limits of CFD technology by simulating real track

conditions with increased accuracy. Based in a newly constructed sub-terrain facility at the Team’s Enstone headquarters, the new supercomputer will be used, almost entirely, to run simulations using STAR-CCM+: “In 2008 we signed a three year partnership with CD-adapco. An important part of this is the increased access that we gained to CD-adapco’s expertise”, says Jarrod Murphy, Head of CFD Department at ING Renault F1 team.

“STAR-CCM+ is a state of the art CFD code that’s relatively new and is fast, robust and extremely easy to use”.

The design of a race car is a continuous iterative process that starts with review of both CFD and wind tunnel test data together with telemetry data gathered from the car. Based on those observations the new geometry is then either generated or re-designed using CAD (computer aided design), the team of aerodynamicists then develops a collection of possible configurations which are analyzed using CFD. This iterative process of surface optimization includes surface clean up, mesh generation and numerical calculation yielding the final aerodynamic loads. In the intensely competitive environment of Formula 1, in which new modifications are often unveiled on a race by race basis, it is important to make this iterative process as automated as possible so that engineers can focus on analysis and innovation rather than manually preparing CFD calculations. A significant advantage of STAR CCM+, over any other CFD tool, is that the whole process is completely automated from the point of g

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..::FEATURE ARTICLE Automotive

CAD geometry import through to report generation once the solution is complete, a feature of STAR CCM+ that Jarrod Murphy outlines as a key attribute: “Model update time is significantly reduced due to the automated mesh pipeline functionality of STAR CCM+. It is very robust and always produces a high quality volume mesh with no user input. These features make STAR CCM+ ideal for design optimization”.

Repeatability of computational model creation is also critical as the front and rear wing, brake ducting or wing endplates are liable to change on a race by race basis. When it comes to the constantly evolving design of these components, turnaround time is critical, the associative nature of settings inside STAR CCM+ means that modified components are easily replaced and the volume mesh regenerated automatically with exactly the same settings, dramatically reducing run-times and significantly improving engineering output.

In the case of deflection sensitive component, such as the front wing, where proximity to the ground is a critical parameter, the results the aerodynamics loads are automatically passed to ING Renault F1’s structural analysis group to determine stress levels on the new components, as well as structural integrity and deflections. The deflected shape is then passed back to the CFD department so new aerodynamic loads and balance may be assessed. Finally, the components are evaluated at race track testing days which is usually final step before they end up on the race car (although from the beginning of the 2009 season, testing restrictions will seriously limit this capability)..

Although the primary use of CFD technology is aerodynamic analysis, it also has many other uses within the car’s design cycle. The study of thermal management is another example where CFD is very useful, the full car thermal analysis includes radiator heat rejection, exhaust gas blowing and front and rear brake disc heat rejection. Proper investigation into location and magnitude of these hot air flows is critical as the structural integrity of components may be compromised if over-heated. The most obvious location where this can become a serious problem is on the rear wing whose temperature may be increased significantly due to the proximity of exhaust plumes. These thermal analyses are almost exclusively carried out using CFD, as wind tunnel testing

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of such flows and the reproduction of temperatures experienced during racing is extremely complex.

With recent restrictions in wind-tunnel and track testing, CFD is playing an even more critical role in the development of Formula 1 cars, last year at the ING Renault F1 team, CFD was responsible for 10-20 percent of the increased aerodynamic efficiency of the car as the season progressed. This year, with a new supercomputer available to the team and the advanced features of STAR-CCM+ software, they expect much more than that.

“A key factor”, says Jarrod Murphy, “in the strength of CFD at ING Renault F1 team is the close partnership we have developed over the years with CD-adapco. I am continually impressed with CD-adapco in terms of support and their willingness to take on board development requests. STAR-CCM+ is being developed at a very fast rate and very often it is only a few months before a particular request from ING Renault f1 has been incorporated into the production code.” <

..::FEATURE ARTICLE Automotive

r ING Renault F1 Team unveils the R29 in Portugal The ING Renault F1 Team officially launched its 2009 season on the 19th January as the new Renault F1 R29 was unveiled to the world’s media at the Algarve Motor Park near Portimao in the south of Portugal.

With radical revisions to the sport’s technical regulations introduced this year, the R29 incorporates a new design philosophy and looks very different from its predecessor. Great attention has been paid to maximizing the new rules and the team is optimistic about its chances for the year ahead, as Flavio Briatore explained: “We began our preparations for the R29 project early and I am proud of what the team has achieved. There are lots of new things to deal with this year, which could shake things up, but we intend to continue fighting at the front. We will now concentrate on our final preparations for the start of the season so that we can arrive in Australia hopefully fighting for the podium.”

i MORE INFORMATION ON ING RENAULT F1 TEAM http://www.ing-renaultf1.com

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❐ FACTS Points schedule for most Formula SAE events Design Event

150

Cost & Manufacturing Analysis Event

100

Presentation Event

75

Acceleration Event

75

Skidpad Event Autocross Event

50 150

Fuel Economy Event

100

Endurance Event

300

Total Points Possible

1,000

Formula for success James Guitar - Michigan State University Dejan Matic & Lauren Wright, CD-adapco.

Attracted by its versatility and accuracy, The Michigan State University (MSU) Formula SAE team is using STAR-CCM+ to design a 2009 Formula SAE race car.

Every year in May during the first week of summer school break, students from 120 Universities descend on Detroit Michigan for a unique competition. For one week only, the Michigan International Speedway becomes the international centre of young engineering talent as hundreds of hours of work (and occasional sleepless weekend spent in the school machine shop) come to fruition. The outcome of this dedication is a formula style race car designed and manufactured entirely by students. With strictly defined rules and regulations, students produce a completely new race car every year.

The competition bears name of the Society of Automotive Engineers (SAE), which organizes and governs the event, and provides leading specialists from the automotive industry as judges. Established in 1981 by the University of Texas, the first Formula SAE competition attracted just a handful of Universities from the United States. Since then it has become a widely recognized international University program that inspires students from all around the world to excel in theengineering challenge of race car manufacturing. It is an international competition with venues in Australia, Japan, USA and Europe.

Some of the most successful challengers outside of the United States come from Germany, Australia and the UK. Soon after inception of Formula SAE, the automotive giant General Motors began to take notice of the competition followed by Ford and then Chrysler.

Realizing the potential behind this program, the competition became jointly staged by a consortium with representatives from these three car manufacturers. Besides the challenging competition, it is also a place for the professional recruitment of entry level engineers, many of the recent graduates find a job with one of the team sponsors immediately after the completion of their

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course. For any student with aspirations for further involvement in the car racing industry, Formula SAE represents an important first step.

The answers to the usual three questions that casual spectator asks about Formula SAE are “130mph”, “$200,000” and “No” where the last question is “Can I drive it?”. The price of the race car is calculated taking into consideration material, tools and the number of man-hours team members put into the project. The top speed of 130mph greatly depends on aerodynamic properties of the car, more precisely if the car has wings or not. Many schools decide not to develop aerodynamic devices and benefit from the reduced car weight.

Even though the car performance compares well with its more famous relatives from the world of professional racing, the Formula SAE competition is more of an engineering challenge than traditional track race. The competition includes a combination of dynamic and static events such as autocross, drag racing and a design event, during which every car is scrutinized by the judges and marked against a range of criteria. During the design event students are tested on their knowledge of physics, vehicle dynamics, aerodynamics or material science and asked to defend their design ideas.

The race car is powered by a production motorcycle engine, the power of which is limited by an air intake restrictor for safety reasons. This usually requires some adaptations since the computer program that governs the amount of fuel injected into the engine cannot compensate for the reduced aspiration. In order to maintain maximum power throughout the whole range of engine speeds, students have to build a new fuel injection map. This is where the CFD simulation of engine intake comes into its own, with the engine dynamometer available, MSU Formula SAE students can easily validate the CFD results and then expand on them introducing variations into intake design. g

..::FEATURE ARTICLE Automotive

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r Thinking globally is at the heart of MSU’s dedication to forming partnerships with institutions around the world that share our commitment to enhance education, health, agriculture, business, and technology.

As the world grows smaller, the university’s reputation as a leader and sought-after partner in international academia, research, and economic development becomes ever more vital.

p ABOVE The final production car ready for entry into the competition.

Instead of taking time and money consuming efforts of building physical prototypes, they can optimize the air intake design using the latest computer technology and then build the one that has the best performance.

Despite the usefulness of CFD analysis in optimizing intake design, the main application of STAR-CCM+ at MSU is external aerodynamics.

“The main purpose for using STAR-CCM+ is to reduce the aerodynamic drag while increasing the downforce, or at least keeping it constant. This year we are specifically focusing on optimizing the sidepods as they are one of the biggest contributors to the aerodynamic drag” says James Guitar, head of Aerodynamics. “The sidepod optimization includes the positioning of the radiators as well as finding suitable location and size of the openings to ensure that there is an even distribution of pressure across the face of the radiator and no reverse airflow inside the sidepods themselves.”

“We are also paying great attention to the undertray design, the main purpose of which is to reduce turbulence under the car and, by extension, reduce the aerodynamic drag.” The undertray design features two expanding tunnels in the shape of a diffuser that twist between the driver, engine and rear tires. The tunnel size, diffuser angle of attack and inlet-outlet ratio are determined using STAR-CCM+ taking into consideration packaging constraints and the ground effect. “We are hoping to make a significant increase in the level of downforce. We find STAR-CCM+ very intuitive, easy to learn and implement which enabled us to make a number of design changes in the early stages of the software implementation.”

The Formula SAE race cars are usually made of steel tubular frame to which the engine sub-frame, bodywork and suspension members are attached.

Calculating the flow around the car was traditionally very difficult, as it often consisted of many small details and “dirty” CAD data containing poorly triangulated, overlapping or disconnected surfaces. To repair these surfaces manually would consume many man-hours of stiching and repair in order

to obtain a high enough quality surface mesh required for CFD analysis. In STAR-CCM+, this task can be achieved automatically by simply deploying the surface wrapping tool. “We are particularly happy with automated meshing capabilities of STAR-CCM+, it greatly reduces simulation set up time for the multiple geometry configurations that we are analyzing.”

The standard k-epsilon model was applied, and the steady state flow around the car was simulated in order to properly resolve the flow under the car, the moving floor and rotating wheels were set as boundary conditions.

The model consisted of approximately one million trimmed cells with prismatic layers strategically located in the zones of high pressure and velocity gradients.

To help resolve the flow features around the complicated car geometry, volume refinements were used.

As well as the aerodynamic analysis of the car, STAR-CCM+ was also used to model sloshing in the fuel tank using the Volume of Fluid (VoF) model helping the MSU students predict liquid movement in the fuel tank and engine oil pan while the car experiences high inertial forces in corners or during acceleration and braking. As the fuel and engine oil are pulled away from pumps, careful fuel reservoir and engine sump design prevents starvation of these fluids enabling maximum engine power and proper lubrication of moving parts inside the engine.

“STAR-CCM+ has really opened up a new realm of possibilities for our car”, says Guitar, “being able to use this software for external simulations, restrictor design, oil reservoir and gas tank sloshing will help to improve our vehicles performance and overall design.” <

i MORE INFORMATION ON The Michigan State University http://www.msu.edu/

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Automated Flow, Thermal & Stress Simulation for the Automotive Industry 3

Productivity

3

Accuracy

3

Flexibility

What do you expect from your Engineering Simulation Software?

VISIT OUR STAND AT THE FOLLOWING EVENTS: SAE World Congress 2009 - April 20-23, 2009, Detroit, MI 29. Vienna Motor Symposium - May 7-8, 2009, Wien, Germany Engine Expo - June 16-18, 2009, Stuttgart, Germany SAE 2009 Commercial Vehicle Engineering - October 6-8, 2009, Rosemont, IL

For more information: info@uk.cd-adapco.com www.cd-adapco.com/automotive

3

Expertise

..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Automotive q BELOW The modified car in the VZLU open section wind tunnel.

Track Car Aerodynamics q BELOW Experimental wind tunnel results were compared to computational models.

v Fig:03a-c Streamlines showing the improved heat exchange of both radiators, thanks to the good quality of air flowing through them.

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..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Automotive

p ABOVE Streamlines and pressure contours on the modified car.

Stepan Zdbinsky, Aeronautical Research and Test Insititue, Czech Republic.

Fans of motorspor t increasingly want to get a taste of what it feels like to go bumper to bumper with other race cars in a competitive environment. While the dream of owning a top spor ts car might be beyond the reach of the average armchair racer, an increasing number of companies offer the general public a chance to feel the adrenalin a high power car and a strip of tarmac brings, allowing clients to try out a days racing without having to invest large sums of money.

There is little doubt that a single seat race car offers the ultimate racing experience. Unfortunately the skills required to control such a vehicle combined with the costs to design and maintain one means that single seaters are outside of the comfort zone for most racers. For many aspiritional racing drivers modified road cars present a more sensible introduction to the world of racing. The Aeronautical Research and Test Institute (VZLU) in Prague was asked to analyze the effect of aerodynamic enhancements on a small hatchback. Such a car represents the ideal introduction to track racing with a good balance of speed and handling with two seats allowing an instructor to accompany the driver.

The geometry The geometry of the car was created using 3D laser scanning to accurately reproduce the complete configuration of the vehicle including three major additional modifications to the standard car: 1. An enhanced underbody and rear diffuser

2. A two element rear wing

3. A modified front bumper incorporating a splitter.

The scanned geometry was read into STAR-CCM+ and split along the symmetry plane so a half model could be analyzed. The surface was then prepared using the surface wrapper and re-meshed before a 10 million cell trimmed mesh was generated.

As well as simulating the full size car, a 1/4 scale model was also created for the purpose of direct comparison with wind tunnel tests that will be carried out in the future. This model will be analyzed in a circular open test section low speed wind tunnel, therefore the tunnel geometry immediately upstream and downstream of the test section was also incorporated into the computational domain.

Analysis The aerodynamic modifications, mentioned previously, were designed to improve the handling of the car, specifically its stability through corners, an essential criteria when novice drivers are learning to race. To achieve this, additional downforce is required as well as (if possible) a reduction in the overall drag of the vehicle. g

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p ABOVE Total pressure contours of the car in the wind tunnel.

The underside modifications and the front splitter addition are designed to reduce drag and increase downforce. Above the front splitter the air dam has the effect of raising the pressure which, combined with the reduced pressure of air accelerated below it, increases the downforce on the front of the car. By ensuring the underbody of the car is a “smooth” as possible not only is drag reduced but downforce increased through a stronger ground effect. The splitter also has the added advantage of increasing the airflow through the front heat exchangers, helping the engine to perform better.

The rear diffuser, fitted in combination with the smoothed underbody, has the opposite effect to the splitter and works to bring the low pressure high velocity air underneath the car back to ambient conditions without inducing extraneous turbulence. If effectively fitted, this will help make the car underbody a more effective downforce generating device while reducing overall drag.

The car studied is a rear wheel drive vehicle, so the addition of a rear wing fitted to the roof of the car, is intended to significantly increase downforce. This has the effect of increasing the stability and drivability of the car through corners as well as improving the ability of the car to transfer power through the rear wheels onto the track.

Effect of aerodynamic modifications Analysis showed that the front splitter has the desired effect, creating a stagnation point and reducing the pressure underneath the car. This, combined with the smoother underbody and rear diffuser, reduces the drag on the vehicle by around 10% while simultaneously increasing the lift by 840N at 230km/h.

The rear wing, placed slightly backwards and below the roof line, delivers a considerable increase in downforce raising it by 1890N at 230 km/h, this gain

p ABOVE Automatic surface wrapping and hexahedral meshing was used to generate the model.

does come at a price, however, as drag is also increased by 6%. Given the critical nature of rear end grip to the handling of the vehicle, the elevated drag is a price worth paying especially as savings have been made elsewhere with the underbody modifications.

Conclusions STAR-CCM+ has helped VZLU study the race modification of road cars to a level of detail not previously possible. Key to the success of the project was the ability to effectively and rapidly mesh a complex aerodynamic body to an acceptable level of accuracy. As the project continues a full analysis of the accuracy will be conducted comparing the computational simulation to wind tunnel tests carried out at the VZLU facilities. <

Výzkumný a zkušební letecký ústav (VZLU) VZLÚ was founded in 1922 as the Institute for Air Navigation Studies under the auspices of the Ministry of Defence. More than 80 different types of Czechoslovak aircraft have passed through the Institute’s labs to date.

Customers from turbo-machinery, car industry, civil engineering and many other industrial branches place their orders for developmental and testing work with VZLÚ. Since 1993 the Institute has been working on R&D programmes tendered by ministries of the Czech Republic and since 1999 on programmes in aeronautics supported by the European Union.

As well as providing computational analysis services, VZLU has a range of test facilities including 4 low speed and 10 trans/super sonic wind tunnels.

i FOR MORE INFORMATION VISIT: http://www.vzlu.cz

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..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Automotive

THE seven Benefits 2008 was a tough year for the auto industry and 2009 is likely to be even tougher if economic predictions prove to be correct. Without exception, auto companies and suppliers are looking harder than ever to improve productivity and cost effectiveness in their product development processes.

CD-adapco is part of the auto industry and has been a significant provider of CAE software and services to the OEMs and their suppliers since 1980. In the early part of the new millennium CD-adapco embarked upon the development of a major new software package, STAR-CCM+, for computational modeling of problems in continuum mechanics. STAR-CCM+ was first released in 2005 and has since matured into the most powerful software available for modeling vehicle aerodynamics and thermal management (VTM) and addresses the issues that are considered to be of the greatest importance to product development organizations. If you work in such an organization and are responsible for delivering aero or thermal solutions, then please consider the 7 good reasons below why you should be looking at STAR-CCM+ if you are not already doing so.

Accuracy is of primary importance in decision making and especially when optimum solutions are sought in a competitive marketplace. STAR-CCM+ embodies state-of-the-art models and numerics to deliver accurate aerodynamics and VTM solutions for both steady and unsteady simulations to ensure that you make the correct decisions.

Breadth of capabilities is critical to deliver a complete solution for all problems.

The accepted industry-standard turbulence models - LES/DES, k-omega SST, Langtry-Menter together with sub-models for fans, heat-exchangers, radiation, conjugate heat transfer, aeroacoustics and much more all come as standard in STAR-CCM+.

Consistency of results is achieved by using a customizable pipeline process, from CAD to Results, which integrates STAR-CCM+ into your organization. Once

the process and pipeline has been defined for your requirements, it may be executed repeatedly for both new designs and design iterations to deliver consistent results whoever and wherever the process is executed. A powerful suite of pre and post-processing tools within STAR-CCM+ ensures consistency of the total process.

Robustness of every aspect of the process ensures that results will be delivered on time, every time, so that decision points are met and product development proceeds on schedule.

Speed to deliver results is being constantly squeezed as product delivery timescales get ever shorter. The automated pipeline execution, fast steady-state and transient solvers for both aerodynamics and thermal solutions coupled to outstanding parallel performance of STAR-CCM+ delivers results in the minimum time possible.

Support from CD-adapcoâ&#x20AC;&#x2122;s global organization provides specialist training, mentoring and a dedicated support engineer, no matter where you are in the world, to ensure that your team is successful.

Value of services is extremely important at all times, but especially in todayâ&#x20AC;&#x2122;s tough economic environment. This is why CD-adapco delivers all of the above in one competitively priced product, STAR-CCM+, there are no hidden extras.

If your organization uses or is considering using aerodynamics or thermal analysis and is not using STAR-CCM+ already, then contact us today!

For more information visit: www.cd-adapco.com/auto

i For More Information visit the new vehicle simulation resource center http://solutions.cd-adapco.com

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❐ FACTS Fuel cells convert the chemical energy of a fuel, such as hydrogen, into electrical energy without combustion, with little or no emission of pollutants and efficient electrical power generation. This is a significant improvement over internal combustion engines Unlike electrochemical cell batteries fuel cells consume reactant from an external source, which must be replenished.

Solid Oxide Fuel Cells (SOFC’s) have a solid ceramic electrolyte, surrounded by anode and cathode electrodes. SOFCs are not sensitive to carbon monoxide, operate at high temperatures, and can run on a variety fuels.

p ABOVE Section showing the five-cell stack model.

Modeling The Future of Power Gen James Ippolito, Dejan Matic & Joel Davison, CD-adapco.

With increasing environmental concerns and rising oil costs, fuel cells are attracting great interest as a por table power source for transpor tation and power generation applications as a cleaner and cheaper alternative to combustion based systems. In recognition of this, CD-adapco in par tnership with the Depar tment of Energy’s Pacific Nor thwest National Laboratory (PNNL), has developed a new Exper t System, es-sofc, which is playing an impor tant role in optimizing SOFC (Solid Oxide Fuel Cell) design. This ar ticle highlights how the es-solution, es-sofc, can be used to explain the behaviour of an SOFC stack.

The modeling of solid oxide fuel cell (SOFC) devices during steady operation to calculate temperatures and stresses, is ongoing and becoming increasingly three-dimensional. The knowledge provided by the modeling of fuel and oxidant flow conditions within the SOFC cell/stack can be used to minimize thermal stresses and maximize fuel utilization, while providing effective thermal management of the system.

A fully three-dimensional, steady-state, CFD study was performed on a 5-cell, planar, solid oxide fuel cell stack with the geometry and experimental data provided by the Institute of Nuclear Energy Research (INER) in Taiwan. The

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computational model contained approximately 1.53 million cells with solid cells used to model the anode-supported PEN, spacers, seals, interconnects, cover plates and external experimental apparatus. The fluid cells were divided into two streams, fuel and oxidant with porous media used to model the nickel (anode side) and silver (cathode side) mesh in contact with the PEN assembly.

As well as the solution of mass, momentum and energy through both the fluids and solids, a number of electrochemical fields are addistionally solved as well as the electric current in the electrodes and electrolyte. The thermal conductivities of the solid SOFC components and porous media were calculated

..::FEATURE ARTICLE Automotive

p Fig:01 Current Density and temperatures in the five stack model (top) with reactants and products (bottom).

p ABOVE Setup of the five -cell stack model.

using polynomial functions of temperature. The density of the fuel and oxidant was determined using the ideal gas law with thermal conductivity and viscosity calculated as a function of temperature and composition.

High concentration hydrogen (93%) was used as the fuel with the remaining constituents being 3% CO, 2% H20, 1.5% CO2, and 0.5% N2, air was used as the oxidant. The inlet molar flow rate for fuel and oxidant was 2.724 x 10-3 and 6.810 x 10-3 moles/s, respectively with an inlet temperature for each stream of 700°C and one atmosphere, respectively. Radiative heat transfer between the side walls of the fuel cell and the oven enclosure was included with the oven walls assumed to be isothermal with a temperature was 750°C. Experimental data provided by INER with the operating point for an average current density of 0.28 A/cm2, an active area of 81 cm2 and a total current was 22.7 A. At this current, the polarization curve showed a total voltage drop of approximately 4.3 V with the experimental temperatures recorded for comparison with CFD results. Temperature was measured at twelve locations by placing thermocouples within the fuel cell.

Input parameters to quantify activation losses were adjusted during the CFD simulation so that the total voltage drop across the five cells reached the target sum of 4.3 V. The voltage drop across each individual cell was predicted by the CFD code and also measured in the lab. Both techniques show a smaller voltage drop across Cell 1 compared to the remaining four cells.

The temperature distribution measured experimentally was one that showed higher temperatures shifted towards (a) the fuel inlet side and (b) towards the top plate. The highest temperatures were found at the top/center thermocouples, T4 and T5, while the lowest temperatures were located near the bottom plate and on the air inlet side, specifically T1 and T3. CFD results matched well with thermocouple measurements. Contour plots, provided by the CFD simulation, for both temperature and current density are shown in Figure 1.

Key performance results such as power density, fuel and oxygen utilization and side-wall heat loss are shown below. Consumption of fuel and oxygen was studied with, the flow distribution to each cell and across each individual, cathode-side channel obtained.

Additional CFD results Power density (W/cm2) Fuel utilization (-) Oxygen utilization (-) Side-wall heat loss - fuel inlet side (W) Side-wall heat loss - thermocouple T2 side (W) Side-wall heat loss - air inlet side (W) Side-wall heat loss - thermocouple T1 side (W)

1.1 22.4 24.6 7.5 8.2 -1.0 8.2

In conclusion, the numerical calculation of the INER five-cell SOFC temperature distribution agreed well with experimental data. The simulation provided valuable insight into the local distribution of flow, temperature, current density and fuel species. <

es-sofc works with STAR-CD, as a specialized virtual design, prototyping and testing environment. Typical issues that can be handled include: correcting the distributions of fuel and oxidant to the stack, mitigation of excessive thermal gradients along with temperature prediction for the calculation of thermally induced stresses, and manifold/flow passage optimization. These aspects together with gaining a better understanding of the electrochemistry and thermal properties involved, lead to optimized solid oxide fuel cell performance.

i MORE INFORMATION: www.cd-adapco.com/products/es-solutions/es-sofc

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Vehicle Thermal Management in STAR-CCM+ John Mannisto & Joel Davison, CD-adapco

Since the first Model T rolled off the famous Ford production lines, the issue of engine cooling has been of prime concern to vehicle designers. Putting an internal combustion engine inside a confined space will always provide a stern engineering challenge, as the explosive combustion of the fuel used to drive the vehicle releases energy not only in its kinetic form but, by the nature of the process, as heat. Ensuring this thermal energy is dissipated in a way that will not harm the components “under the hood” is essential to ensure that your expensive new shiny new automobile makes it beyond the car lot exit!

❐ FACTS

25

For the past twenty-five years leading automotive companies have relied on CD-adapco’s state-of-the-art technology to improve their designs.

STAR-CCM+, STAR-CD and the STAR-CAD Series provide engineers with an advanced and complete CFD toolkit. This unique approach brings unrivalled ease-of-use and automation to CAD preparation, meshing, model set-up and iterative design studies, enabling engineers to deliver better results, faster.

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CD-adapco’s automotive team have pioneered many new application areas as diverse as brake cooling and crankcase analysis. The company has delivered CFD and FEA projects to all the top automotive companies world wide. New product releases, on going training and educational programs are helping customers keep pace with the evolving automotive industry.

..::FEATURE ARTICLE Automotive

STAR-CCM+ has been used extensively to provide insight into cooling performance and engine compartment flow. Up until recently is was common to take these results and use FEA methods to determine component temperatures, often requiring stand-alone radiation plug-ins and fluid structure interaction software. The introduction of STAR-CCM+ has changed this, with CD-adapco’s engineering services team as well as a growing number of industrial users experiencing the benefit of the integrated, automated technology.

A typical scenario where STAR-CCM+ simulation can deliver tangible benefits is in the analysis of components failing post-production, for example: A new controller box is installed on a firewall or truck rail, and although testing was performed to ensure adequate cooling, warranty claims begin to surface six months into product release. At this point, the damage is done; production is in full swing, months of production inventory are operating in the field, and the process of determining the corrective action has only just begun.

Cases such as these, often handled by CD-adapco’s Engineering Services team, demonstrate the need for timely and accurate temperature prediction of the underhood environment – in the design loop - before the failures start to appear.

In a complex environment such as an underhood, there are numerous design developments running simultaneously. For example, modifications to the emissions system (i.e. turbo, EGR coolers, piping) may trigger corresponding changes to the fuel controller, and possibly changes to the packaging. Because

the changes to the design are being developed concurrently, it is not difficult to invision a scenario where, for example, an electronic component is mounted in an area that will be exposed to a re-routed exhaust pipe, Another example is the new DPF/SCR/Urea systems being used on trucks which are extremely large, and get very hot (especially during the regeneration phase). Locating these units to minimize interaction with other components (including vehicle occupants) is a challenge that requires so many factors that it is simply not practical to use traditional build/test/fail methods for optimizing their location.

The Sky is The Limit The technology applied to the analysis of automotive underhood environments can be extended to any situation where the accurate prediction of thermal fields is of vital importance.In passenger jets, flow under the floor, cockpit and passenger areas is integrally linked. Thermal behavior will depend on a multitude of factors, from the power output of the electronics to the conductivity of the carpet. Cooling requirements for the avionics have to be balanced with the pilot/ passenger comfort requirements, icing issues in fuel lines need to be addressed and Boat-end APU’s and “boiler room” electronics can interact unpredictably.

Simulating both the flow and thermal behavior of these complex environments can identify the issues earlier in the design, while there is still some flexibility in the packaging.

The methodology may also be applied to static objects such as a “GENSET”.

By coupling an engine to an electric generator, these GENerator SETs can g

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❐ NEW AUTOMOTIVE CENTRE

www.cd-adapco.com/auto Automotive Application Centre For the past twenty-five years leading automotive companies have relied on CD-adapco’s stateof-the-art technology to improve their designs.

STAR-CCM+, STAR-CD and the STAR-CAD Series provide engineers with an advanced and complete CFD toolkit. This unique approach brings unrivalled ease-of-use and automation to CAD preparation, meshing, model set-up and iterative design studies, enabling engineers to deliver better results, faster.

CD-adapco’s automotive team have pioneered many new application areas as diverse as brake

provide portable, compact electric power to remote locations such as construction sites or a military field camps. Reliability of these units is a premium requirement, and the environmental conditions can vary from a desert battleground to an arctic drilling site. Anticipating the thermal behavior of these systems in environmental extremes is something easily modeled using CFD and reduces the need for costly and time consuming environmental chamber testing.

The use of STAR-CCM+ is not restricted to terrestrial objects either with the thermal performance of satellites also extremely important. The thermal loads generated by electronics systems can be combined with radiation heat transfer not only internally but due to the extreme solar loads experienced outside of our atmosphere. To develop an understanding of the cooling requirements for this harsh environment, heat generation is applied down at the chip level, to accurately characterize the temperature distribution at the board level.

Clearly, the vehicle thermal simulation is extremely important, regardless of vehicle type, and the Engineering Services Team at CD-adapco saw this type of simulation as an important service opportunity. We outlined our goals, established methods, and the choice of software was obvious: STAR-CCM+ Our goal is a virtual vehicle that can provide overall thermal assessment, as well as sub-system or component thermal studies. The methods needed to achieve this have to be accurate, flexible and of a short enough turnaround time to stay within the design loop. There are two primary methods for combining underhood and thermal prediction, each offering different advantages: A full conjugate model can provide the best characterization of the fluid/solid thermal interaction but requires a high quality CAD model and large amounts of computer power.

The explicitly coupled models offers the advantage of

simpler modeling requirements, and the ability to work both flow and solids models independently. This also results in two models with more manageable sizes, although the coordination effort between models now increases.

We have found application for both methods. The choice is influenced by the client, and includes several factors: computing resource, quality of CAD, even organization of engineering teams.

Since the temperature prediction work has traditionally been performed by the “thermal/stress” groups, it has often been done using FEA methods. At CD-adapco, the Thermal-Stress Engineering team has traditionally used this technology but the recent advances in finite volume stress and automated CAD preparation and meshing has meant a move to STAR-CCM+ for the conduction/radiation problems. This integrated approach means that no FEA, FSI coupling software or radiation plug-ins are required, even with the explicit coupling approach.

The VehTherm model sizes are kept to an efficient size by a significant new STAR-CCM+ enhancement: thin solid meshing. The technology will automatically identify components that are thin-walled in shape, and make use

cooling and crankcase analysis. The company has delivered CFD and FEA projects to all the top automotive companies world wide. New product releases, on going training and educational

q BELOW The single integrated environment and new part feature of STAR-CCM+ drastically reduces model preparation time for component thermal analysis

programs are helping customers keep pace with the evolving automotive industry.

Vehicle Simulation Resource Center Want to know how we are impacting auto companies world-wide?

Visit our Automotive resource center for customer examples highlighting applications like: • Aerodynamics • Fuel Cells • Powertrain • Vehicle Thermal Management • Passenger Comfort and Aeroacoustics • Aftertreatment

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..::FEATURE ARTICLE Automotive of prism extrusions to mesh. Since many body and frame components are sheet metal stampings, this can dramatically reduce the cell count in the model.

Another very important enhancement introduced in STAR-CCM+ 4.02, is the “parts” structure mirroring more closely the organization of the original CAD data. With potentially thousands of parts to assemble, it is important to maintain a sensible hierarchy to the model, and this is addressed by recent developments.

Whatever method used, it is clear that vehicle thermal prediction is a necessary component of the underhood simulation process. It can augment the testing process, reduce the number of design iterations, and avoid costly warranty issues.

For the Engineering Services Team as CD-adapco, using STAR-CCM+ is key to our success in performing this type of simulation. At both the system and component level, the advances in the software and methods have allowed us to provide a service that can truly support the design process, while staying within the design loop. <

❐ TRAINING CD-adapco is pleased to offer a dedicated ‘Engine Compartment Thermal Modeling’ course: Your instructor will guide you through the fundamental approach and best-practices in applying CFD for thermal simulations in engine compartment and underhood environments. This will help increase your knowledge in the simulation approach for full 3D vehicle thermal simulations. During this course, you should expect to learn and understand: • How to significantly reduce simulation turn-around time using CD-adapco’s unique “fast-track” approach for the complete thermal simulation process from CAD to solution.

• JAVA based macro set-up for automation for DFSS and “what-if” type projects • Best practices in generating underhood/engine compartment models including • Critical component temperature predictions (engine mounts, rubber hosing temperatures) • Getting the most out of your thermal models so that final climate wind-tunnel testing is more productive and cost effective.

For more information go to: http://www.cd-adapco.com/training/ p ABOVE & TOP The placement of electronic components near the exhaust system makes thermal analysis a critical consideration.

p ABOVE A new feature of STAR-CCM+ allows the automatic prism meshing of thin features such as heat shields.

i For More Information visit the new vehicle simulation resource center http://solutions.cd-adapco.com

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..::FEATURE ARTICLE Automotive

PDA Location and Notch Size Control factors

Intake Port Diameter Control factor

Separated Length of Primary Control factor

Primary Pipe Shape Control Factor

Original Geometry

Shape of Plenum Volume Control Factor

Angle and Length of Primary Pipe Control Factors

Final Optimized Geometry

DESIGN For Six Sigma Optimization of Engine Intake Manifold Design using Design for Six Sigma (DFSS) Soonseong Hong, Byungkeun Oh & Yongtae Kim - GM Daewoo Auto.

Joel Davison - CD-adapco London, Wondae Jeon & Bongyong Jin - CD-adapco Korea.

Whether it is lean manufacturing, six sigma, or some combination, quality improvement is now a primary focus of vir tually every manufacturer in the automotive industry.

Now that the waste is squeezed out and quality is designed into manufacturing processes, visionary corporations are looking upstream toward the engineering of the product for fur ther gains in quality.

One of the more popular methods for addressing quality improvement during the design process is known as Design for Six Sigma (DFSS).

Like most quality improvement acronyms this process has different meanings for different organizations but, from a “big picture” perspective, DFSS simply means designing products that meet the customers’ requirements while maximizing the efficiency and robustness of the manufacturing or integration process. In this article we explore how CAE can be used to drive a DFSS analysis in the design of an engine intake system.

When condidering the design of a new engine, in order to meet customer expectations of improved performance, an engine designer will typically begin

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with the dual objective of increasing engine performance while simulataneously reducing fuel consumption. In seeking these improvements, one important factor is the combustion efficiency of the engine, which is determined by, among other things, the swirl strength and mass flow rate in the cylinder.

To increase the swirl strength in the cylinder chamber at the mid and low speed range, modern automotive engines frequently use PDA (Port De-Activation) systems integrated into the intake manifold. The port deactivation device induces swirl charge motion in the cylinder (therby improving combustion) but also has the effect of reducing mass flow rate (leading to a corresponding reduction in volumetric efficiency). For this reason the design of any PDA system

..::FEATURE ARTICLE Automotive ❐ FACTS Define Control

Improve

Measure

Analyze

Design for Six Sigma is, in efffect, a problemprevention tool deployed in the design process to avoid the the need for later remediation efforts with the intention of eliminating problems before they occur.

The overiding aim of DFSS is to create products that will meet customer expectations under all foreseeable operating conditions.

p P-Diagram

requires a careful trade off between the improved combustion from the increased swirl and reduction in efficiency caused by a lower mass flow rate. This is where optimization techniques come into their own with the ability to automatically find optimal designs and operating points.

the pressure differences in the mid and low speed range. The control and noise factors along with the signals are combined into a P-diagram to explain the relationship between each factor and the output.

Analysis Computational Model With all the factors in place, an L18 orthogonal array can be compiled to provide The geometry studied consisted of the secondary pipe between the throttle body information about the influence of each factor on the outputs. 18 combinations of and the plenum, the plenum itself, the primary pipe (runner), a single intake port control factors A-H are studied with corresponding variations in the signal factors and valve and a cylinder chamber. A reference geometry was run with the results M and noise factors N, providing a total of 108 analysis points. compare to experiment that showed a 3.37% deviation in mass flow.

The results of these analyses are compiled with the Signal-to-Noise ratio and The optimization of any system requires the consideration of a number of the values calculated and compiled in a table. different factors and simply changing the geometry of the PDA itself is unsatisBy selecting optimal factors, a 1.43dB gain was obtained in the S/N ratio of factory as upstream and downstream geometries also have a significant effect on mass flow rate and 3.61dB gain in swirl number. The 1.43dB gain of the S/N ratio swirl and flow rate. With this in mind a total of 8 control factors were considered means the relative variation of mass flow rate was reduced by 15.2% and 3.61dB as follows: gain of the swirl number means the relative variation was reduced by 34.1%.

A: PDA location - 2 levels Although the optimal beta value of mass flow rate increased by 0.3159dB B: Inner diameter of intake port - 3 levels gain, swirl number slightly decreased by 0.1094 unexpectedly, this is because C: Notch size of PDA flap - 3 levels the selection of optimal factors was driven primarily to reduce the variation of D: Separated length of primary pipe end - 3 levels swirl needed for stable combustion while increasing the engine speed from low E: Shape of primary pipe section - 3 levels to mid rpm.

F: Angle of primary pipe - 3 levels G: Shape of plenum volume - 3 levels Conclusion H: Length of primary pipe - 3 levels The implementation of DFSS in the current study has demonstrated that the

techniques initially developed in the mid 80s to optimize manufacturing As well as the above factors which are under the direct control of the engineer techniques and systems may be successfully migrated to design studies using there are also “noise factors” which will affect the performance of the engine modern simulation technology. By applying DFSS to the current study an optimized directly but are beyond the control of the designer. In this case the noise factor design for an intake manifold has been found. < considered is the inlet temperature which is set to -30°C and 40°C respectively.

The pressure difference between the intake inlet and the cylinder outlet were used as the “signal factors”, which are used as input data to the DFSS process.

In the current study the signal factors are 1kPa, 4kPa and 7kPa, representing

i MORE INFORMATION ON GM http://www.gm.com/ http://www.kr.cd-adapco.com

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Simulate To Understand CFD helps to understand the history and evolution of racing techniques: the 1973 Ferrari “Spazzaneve” [Snowplough] Marco Giachi, Eng., Centro Studi Storici di Assomotoracing.

Dr. Anthony Massobrio, CD-adapco.

One of the most interesting aspects of competition motor racing is watching the gradual development of the vehicles’ technical features over the years, the most impor tant of which provide a snapshot view of leading aerodynamic design thinking of that time. It is impor tant to know the history of motor racing technology not only for purely cultural reasons, but for educational reasons too, in order to train young engineers and future aerodynamics designers.

Numerical simulation provides an extremely useful tool for reviewing the decisions made; not for criticizing or judging, but for interpreting and understanding the problems encountered and the inspiration, of the designers of the past. With this in mind Assomotoracing and CD-adapco set about studying the 1973 Ferrari Spazzaneve.

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..::FEATURE ARTICLE Automotive

CULTURAL ASSOCIATION OF THE HISTORY AND TECHNIQUES OF COMPETITION MOTOR RACING Founded in 2006 with the aim of promoting the technical aspects of competition motor racing, Assomotoracing is a non-profit-making cultural association that operates nationally but has contacts abroad, mainly with the English speaking world. In the first two years of its life, it took part in a large number of trade shows and conferences, including the coordination of Technical Sessions at Motorsport Expotech event in Modena (the first exhibition for car and motorcycle operators “in the racing industry”), as well as publishing its own journal (R&T – Racing & Technologies).

Assomotoracing’s Historical Studies Centre deals with the historical aspects of technological development with the association’s activities carried out mainly in collaboration with external bodies, companies and universities.

Recently, however, the Historical Studies Centre has been equipped with a computer centre in order to independently carry out less computationally demanding research, while external contributions (especially from CD-adapco) will be used for the more demanding and complex simulations.

Numerical simulation - CFD for the aspects linked to aerodynamics - can be extremely helpful in studying the history of motor racing technology in order to review the choices made by designers over the years, understand them, interpret them and calculate their effectiveness, all aspects of primary importance when training young engineers. The work started with a careful study of structures through a review of original drawings, notes taken from the existing models and research into historical documents (giving preference to those from the same period as the vehicle being studied) and concluding (where possible) with meeting the designer, in order to exchange comments on and discuss the work carried out. These same designers were also often involved before the final discussion, so that they could be consulted at all stages of the research.

At the end of 1972, Ferrari was not performing very well, their last drivers’ world title had been won eight years earlier by John Surtees and in the second half of the nineteen-sixties, the British teams (the “garagists” as Enzo Ferrari used to call them, meaning small stables of assemblers which, in his opinion, were not true builders of racing cars) had driven the Maranello House into a tight corner. Ferrari’s Formula One progamee was not without its technological

successes. At the 1968 Grand Prix in Belgium, Ferrari introduced wings with “gently” lifting spoilers at the barycentric point, however during this time aerodynamics research was principaaly conentrated on sports vehicles with covered wheels.

The Engineer Mauro Forghieri, Technical Director of Ferrari’s Sports Management for nearly thirty years, explained that “…at that time, numerical simulation was still a long way off and we often went to the Wind Tunnel at Stuttgart University. We were all really surprised at the effect of aerodynamics on performance for F1, but it was thought that the sports car’s greatest potential was in the larger surface area on the base of the bodywork. It was not exactly the ground effect, because it was still considered better to work on the upper part of the bodywork and less on the lower, but the idea of exploiting the whole body of the vehicle and not just the wings in order to produce a vertical load was already taking shape…”.

The “Snowplough” was created with this in mind and marked the shift from the “torpedo” single-seater shape to a “wide body”, which would lead six years later to the ground effect of the Lotus 79. Its aim was not only to verify aerodynamic theories, but also the dynamics of the vehicle with its extremely short wheelbase, which simulated the polar inertia of a transverse gear as would appear two years later on the T type Ferrari series, winning three drivers’ titles with Niki Lauda (1975, 1977) and Jody Scheckter (1979) and 4 construction titles (1975, 1976, 1977, 1979).

Numerical simulation started from the generation of the 3D vehicle geometry thanks also to the support of the vehicle’s current owner who very kindly provided his collection of original engineering drawings as well as the vehicle itself enabling the study of structural components not visible on the drawings. To create a CAD reconstruction, we benefited from the designers’ contribution of the MG Model, a company that created special collectors models and had considerable experience as well as an archive of special CAD of the vehicles from the nineteen-sixties and seventies. For CFD simulation we were assisted by the computer workstation at the Assomotoracing Historical Studies Centre supported by the “strategic” consultations of the Engineer Lucia Sclafani of CD-adapco. g

❐ FACTS

The “Snowplough” - 1973

1973 Constructors Championship final standings

Constructor Chassis 1.

Lotus-Ford 72D 72E 2.

Tyrrell-Ford 005 006 3.

McLaren-Ford M18C, M19C, M23.

4.

Brabham-Ford BT37, BT42 5.

March-Ford 721G, 731 6.

Ferrari 12B2, 312B3

Engine Ford Cosworth DFV Ford Cosworth DFV Ford Cosworth DFV Ford Cosworth DFV Ford Cosworth DFV Ferrari 001/1 & 001/11

Points Wins 92 (96) 7 82 (86) 5 58 3 22 14 12

7.

8.

9.

10.

BRM P142 Ford Cosworth DFV Ford Cosworth DFV Ford Cosworth DFV

12 9 2 7 1 2

BRM Shadow-Ford Surtees-Ford Iso Marlboro-Ford

P160C, P160D, P160E DN1 TS9A, TS14A FX3B, IR

Podiums 15 15 8 2 2

Poles 10 3 1

1

v ASSOMOTORACING is a non-profit democratic association, providing educational services to anyone interested in studying the history and technological developments of the motor racing industry. The organisation provides lectures to universities, technical high schools, museums, and trade shows both in Italy and abroad.

Members of ASSOMOTORACING are not only individuals and companies with specific technical knowledge but anyone with an interest and passion for motor racing.

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..::FEATURE ARTICLE Automotive

q Fig 01 Pressure distribution across the car.

t Fig 02 Detail of the trimmed cell mesh.

The CFD model was prepared using the surface wrapper to remove the imperfections on the CAD surface. A volume mesh was then created consisting of 1 million trimmed cells (Fig. 2) and two prismatic layers limited by an average value of y+ of approximately 40. The validity of this modeling was verified in advance, also in the educational spirit of Assomotoracing activities, by simulating the “Ahmed body” in order to check the CFD model’s ability to correctly evaluate the pressure distribution (the primary focus of the research). The car’s trim was of a sufficient distance from the ground (during static conditions, it measured 100 mm) and for this reason the simulation was carried out on solid ground.

The results of the calculations on the “Snowplough” confirm engineer Forghieri’s theories. The upper surface of the bodywork (Fig. 1) has a higher pressure than the bottom which is perfectly flat. The rear of the car decreases in width to increase flow between the gearbox and the rear wheels, a practice which became established in the design of formula one cars in the 1980s, the so called “Coca-Cola” shape (Fig. 3).

The “Snowplough” was retired at the end of 1973 after providing its designer with the information for which it had been designed and created, not only in terms of aerodynamic performance, but also details of more general dynamic behaviour relating to its extremely low moment of polar inertia. <

t Fig 03 Streamlines demonstrating the effect of the “Coca Cola” shape of car.

i MORE INFORMATION ON ASSOMOTORACING http://www.assomotoracing.it/

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..::FEATURE ARTICLE Marine Loads on Ship Hulls The hulls of ships are subjected to a number of loads.

• Even when sitting at dockside or at anchor, the pressure of surrounding water displaced by the ship presses in on its hull.

• The weight of the hull, and of cargo and components within the ship bears down on the hull.

• Wind blows against the hull, and waves run into it.

• When a ship moves, there is additional hull drag, the force of propellors, water driven up against the bow.

• When a ship is loaded with cargo, it may have many times its own empty weight of cargo pushing down on the structure.

If the ships structure, equipment, and cargo are distributed unevenly there may be large point loads into the structure, and if they are distributed differently than the distribution of buoyancy from displaced water then there are bending forces on the hull.

❐ FACTS

r Aker Yards Marine (AYM) is a consulting naval architecture and marine engineering company with offices in US and Canada established to serve the marine community in North America and selected international markets. It is a wholly owned subsidiary of one of the oldest ship makers in the world - the Aker Yards ASA from Norway whose experience spans over a century of exceptional ship building history. The services provided cover wide range of marine industry sector including all aspects of ship design and production technology. In addition, AYM has specialized teams of analysis engineers whose expertise in Computational Fluid Dynamics (CFD) serves to provide practical and cost-effective approach in marine designs.

CD-adapco is proud to announce that its CFD simulation technology has been successfully validated and used at AYM for number of years providing accurate modeling of virtually any conceivable fluid flow. It played a key role in analysis of variety of projects, from hull form optimization or propeller design to ferry car deck ventilation. Selected accomplishments are described below.

p ABOVE Faired skeg with less vorticity along bottom and no flow separation at trailing edge.

>> CASE STUDY 01:

t LEFT New skeg design, showing flow detachment along trailing edge of skeg and strong vorticity along bottom edge.

Validating Hull Performance using CFD Dan McGreer, Aker Yards Marine.

During two recent projects, Aker Yards Marine was requested to evaluate the impact of different design parameters on vessel per formance. The first analysis was to determine whether the location of a ship’s keel coolers had a detrimental effect on propeller inflow, and the second analysis was to determine the impact of skeg geometry on vessel per formance.

CD-adapco’s RANS software was used to evaluate the impact of keel coolers on propeller inflow. Two CFD models of the new hull form with and without keel coolers installed were developed. These two models were compared against three models of existing proven hulls which were developed to serve as a control group. By comparing the turbulence seen on the five different hulls, the impact of both the new hull form and the proposed keel cooler location could be evaluated. The results of the flow simulation showed that the location chosen for the keel coolers had no significant effect on the extent of turbulence generated by the new hull.

The disturbance caused by the keel coolers was primarily a local effect, and did not extend beyond the hull’s boundary layer. The level of turbulence predicted for the new hull with keel coolers installed was similar to that seen on existing proven designs, and the flow into the propeller is not affected by their installation.

AYM also investigated the impact of a change to the shape of the skeg on an offshore supply vessel’s performance. The skeg had been modified

to accommodate a large stern thruster, and the purpose of the CFD model was to determine what the impact of the different skeg shape would be. To build a suitable mesh around the more complex 3D shape of the skeg, the RANS software package STAR-CCM+ was used. CFD models were made of the new skeg shape for this hull and of a more conventional skeg shape for comparison.

Flow visualization around the new skeg showed that separation and vorticity had increased as a result of the redesign. However, while the skeg shape will increase drag, the extent of the wake was not sufficient to cause problems with propeller inflow, and it was determined that the design would be acceptable.

The use of advanced tools such as STAR-CCM+ gives AYM the flexibility to offer clients alternatives to model testing to determine flow characteristics, and these types of analyses can be integrated into the early design stage.

i MORE INFORMATION ON AKER YARDS MARINE: http://www.akermarine.com http://www.akeryards.com

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p Fig:01 Cross-section of a tank containing LNG, showing computed tank wall temperature.

p Fig:02 CFD simulation in tank containing LNG and cooling down.

>> 02:

Improving Cryogenic Analyses with CFD Carrying cryogenic fluids such as LNG or LPG aboard a ship poses some unique design challenges. The extreme low temperatures of these fluids require low thermal conductivity insulation, and may also necessitate heating in various ship locations to prevent exotic steels from being required throughout the ship’s hull. The accurate determination of the heat transfer between the sea water, outside air, and the cargo is critical to ensure the tank and bulkhead arrangements are feasible.

While steady state heat conduction and natural convection in enclosed simple shapes are problems for which analytic solutions exist, the complex geometry around the cryogenic tanks require advanced methods for accurate determination of the temperatures on steel surfaces in and around the tanks. To determine the required steel grades for use in these applications, and to minimize the requirement for cold temperature steels in the hull structure, AYM performed a Computational Fluid Dynamics (CFD) analysis of flow and heat transfer in ship’s cargo spaces capable of transporting low temperature liquids. The ship’s structure was designed to meet US Coast Guard rules which require consideration of the sea temperature at 0°C and an air temperature of -18°C. Using CFD methods to analyze this problem allowed the accurate prediction of the natural convection, as well as heat conduction through the steel bulkheads.

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The CFD model was generated using STAR-CCM+, a state of the art, unstructured RANS solver. The bulkheads were modeled as conducting baffles, and a high level of refinement was used along the steel surfaces to capture the boundary layer flow, which is critical to accurately modeling natural convection processes. The effect of the cargo was modeled by taking the exterior surface of the tank at the liquid temperature of the cargo. The natural convection process necessitates solving the model using an implicit unsteady solver, and then taking time averages of the temperatures on all surfaces. Since the CFD models were quick to build and analyze, the CFD solutions were used in an iterative manner to guide the layout of cofferdams and bulkheads to minimize the use of exotic steels.

..::FEATURE ARTICLE Marine

CD-adapco simulation technology is widely used and thoroughly validated at AYM. It is excellent for modeling of wide spectrum of fluid flows as well as heat transfer and chemical reactions. In addition, rapid turnaround time from surface model to mesh creation is accomplished using state of the art unstructured polyhedral mesh and surface wrapping. By providing accurate solutions in a time efficient manner it became integral component of our naval architecture and marine design engineering work. p Fig:01 CFD model of stern of ship.

Dan McGreer - Aker Yards Marine

❐ FACTS crabbing (i.e. traversing) is the ability of ships to move sideways while controlling the forward motion. This maneuver can be induced by using a combination of main propellers, pods, rudders, lateral thrusters or other dedicated devices. A reduction of berthing/unberthing time, an increase of safety and agility, less need for tug assistance are only a few examples of the benefits related to good crabbing abilities.

Crabbing Misadventure

>> 03:

Dynamic Positioning Studied with CFD Recently, AYM investigated the effect of the propeller rotation direction on the Dynamic Positioning (DP) characteristics of a supply vessel.

While general rules of thumb exist to guide designers on the effect of propeller rotation direction, the forces generated while in DP mode will vary depending on the hull form, the location of the skeg, and stern thruster location relative to the propellers.

Consequently, it is quite difficult to quantify the actual effect of the rotation direction without conducting model tests. To investigate this effect, AYM created a CFD model of the stern section of the ship using roughly 700,000 cells in the RANS-solver STAR-CCM+, see Figure 1.

The propellers were modeled in both the inboard and outboard turning configurations while the stern thruster was in operation. A crabbing maneuver was simulated by running the port propeller ahead, the

starboard propeller astern, placing the rudders hard over to port and using the stern thruster. The yaw moment and crabbing force were calculated during the simulation as a function of engine RPM. The use of state-of-the-art computing resources and software codes, combined with a wealth of in-house experimental expertise allows AYM to offer CFD analysis for various types of problems, such as the above study. In the past, AYM has performed CFD analyses for engine room ventilation studies and pressure drop calculations for various ducting configurations. Other studies, such as the reduction of appendage drag, can be handled by our engineering team, with rapid turnaround times from CAD concept directly to CFD solutions. <

q Fig:02 Section through propeller plane.

i MORE INFORMATION ON AKER YARDS MARINE: http://www.akermarine.com http://www.akeryards.com

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Submarine ManeVUering Simulations Office of Naval Research, USA. Dejan Matic, Bill Clark, Ganesh Venkatesan, CD-adapco.

p Fig:01 Mesh resolution on propeller and control surfaces.

37

The numerical simulation of submarine maneuvering is a challenging problem that has only recently been addressed by technological advances in commercial Computational Fluid Dynamics (CFD) software. In this ar ticle, we demonstrate how CD-adapco’s simulation technology can be applied to accurately predict how a submarine’s motion is driven by hydrodynamic forces, and compare numerical results with experimental data.

The physics-based simulation of a full-scale submarine performing maneuvers is an expensive proposition relative to many CFD applications. This is principally due to the wide range of length and timescales that must be resolved in order to predict accurately the flow around the submarine hull. An additional challenge involves representing the full geometric complexity of an appended submarine and propulsion unit. The length scales range from the very thin boundary layer to the full length of the submarine. The time scales range from a fraction of the propeller blade passing period to the total duration of a maneuver - more if several maneuvers are combined in a single simulation. These

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disparities in scale lead to very large computational meshes and simulation times that, until recently, have challenged the state of the art in computational resources.

The submarine in question is propelled by a three-bladed rotating propeller. Maneuvers were executed through the application of rudder and stern planes, and controlled by varying the position of these control surfaces in response to the submarine motion predicted by the simulation.

Numerical method

During the course of a maneuver, the submarine changes its position and orientation continuously in time in response

..::FEATURE ARTICLE Marine

r The Office of Naval Research (ONR) coordinates, executes, and promotes the science and technology programs of the United States Navy and Marine Corps through schools, universities, government laboratories, and nonprofit and for-profit organizations.

It provides technical advice to the Chief of Naval Operations and the Secretary of the Navy and works with industry to improve technology manufacturing processes.

p Fig:02 Surface pressure distribution with streamlines.

to the pressure field generated by application of the control surfaces. The simulation of a maneuver requires the coupled solution of equations of motion of the rigid body (in six degrees of freedom) with unsteady Reynolds-averaged Navier-Stokes equations (URANS). The URANS solver uses a fully-implicit iterative time-integration scheme. It computes the flow field around the body first and integrates the computed shear stresses and pressure distribution on the surface of the body, providing the hydrodynamic forces and moments acting on it. The equations of motion are then solved in order to obtain instantaneous displacements and rotations. This information is used to update the computational mesh which is rotated and translated as a rigid body with respect to an inertial frame of reference.

The integration and rigid body mesh movement are performed automatically using CD-adapco’s Dynamic Fluid-Body Interaction (DFBI) model at each iteration.

By converging this iteration process at each time step, the trajectory of the body is obtained. The implicit nature of the method (in which equations of motion are calculated simultaneously with the flow field) is important to ensure the overall stability of the simulation without using an impractically small time step.

Computational mesh The discretized domain consisted of 3 million computational cells, including layers of prismatic cells next to the walls, which was prescribed in order to capture the near wall boundary layer. The mesh was automatically constructed using CD-adapco’s automatic hexahedral meshing methodology: a simple background hexahedral mesh was created within the boundaries of the computational domain, overlapping the geometry of the submarine. Any hexahedral cells that were located completely inside the body or the extruded layer were deleted, while those that intersect this layer were trimmed so that any overlaps were removed. Finally, the mesh was locally refined in regions where large flow variations were expected.

The propeller was enclosed inside the cylindrical mesh block that rotates about the propeller axis, with a sliding interface between the cylindrical mesh block and the surrounding fluid domain. Rudder control surface motions were accounted for by using mesh distortion. As the rudder is deflected to a new position at each

p Fig:04 Comparison of predicted in-plane trajectory of body center-of-gravity with measurements for horizontal overshoot maneuver.

time step, the mesh in this structured block is locally deformed and smoothed. By employing this procedure only a single computational mesh had to be generated for the entire simulation - rather than creating several meshes for various rudder positions and interpolating between them. Because the rudder mesh motion was integrated into the solution process, less user input was required.

Maneuvering simulations For the case of constant heading and large depth, the submarine is assumed to be traveling through an infinite domain of stagnant water. The motion of the submarine is controlled by a 3-bladed propeller, rudder and stern planes. The entire computational mesh including the submarine body is assumed to be moving with the body without any deformation. The flow field computations were performed in the inertial frame of reference, which makes the specification of boundary conditions easier. Since the body moves through infinite volume of stagnant water, the velocity specified at the far field boundaries of the computational domain is zero.

For the case of horizontal overshoot maneuvering, the top and bottom rudder surfaces were actuated to initiate the maneuver. In the experiment, the rudder was first deflected to 10 degrees and held in this position until the body reached a yaw angle of 30 degrees. The rudder was then reversed.

Figure 2 shows predicted pressure distribution on walls and streamlines behind propeller. Predicted time history of roll, pitch and yaw angles show good qualitative agreement with measurements, see Figures 3 and 4.

Conclusions Good qualitative agreement has been shown between predictions and measurements for the studied maneuvers. The results obtained demonstrate the suitability of the present methodology for the simulation of submarine maneuvers and motion of similar underwater autonomous vehicles. CFD simulation tools will help engineers to optimize the design and analysis process and improve the maneuvering capabilities, survivability and cost of submarines. <

i MORE INFORMATION EMAIL: minyee.jiang@navy.mil

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..::FEATURE ARTICLE Marine

Simulation of Lifeboat Launching Under Storm Conditions Hans Jørgen Mørch, CFD Marin and Agder University, Norway.

Sven Enger, Milovan Perić and Eberhard Schreck, CD-adapco.

Lifeboats are an impor tant component of safety measures for the passengers and crew of floating vessels and offshore platforms. They need to be designed so that people on board can be evacuated safely. This requires that: the lifeboat is not damaged during water entry; the lifeboat moves sufficiently far away from the launching point before its own propulsion system is star ted; and the accelerations experienced by occupants do not exceed a cer tain level over a cer tain period of time.

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..::FEATURE ARTICLE Marine

In the past, lifeboat designs have been tested solely by experimental means. In these experiments, pressure is measured at a certain number of locations on the hull, and motion and acceleration is recorded. However, due to a large number of different lifeboat sizes and a large variety of conditions under which they may have to be used, the number of necessary tests becomes unmanageable.

Experiments may also be deficient due to the following reasons: • In model tests the scale factor should not be less than 1:10 in order to obtain a sufficiently large model to fit sensors and to avoid adverse scale effects.

The maximum wave height in model test facilities is normally less than 1 meter. In order to obtain results corresponding to design waves, one has to rely on extrapolation of experimental results at lower wave heights with the same wave steepness. This introduces additional uncertainty in the results.

• Full scale experiments can only be performed at good weather conditions with little wind and small wave heights, whereas design conditions can have wave heights of 15m and very strong wind. The mismatch between testing conditions and reality makes the evaluation of test data difficult.

• With respect to drop height, model test facilities have limitations given by the height of the ceiling inside the laboratory. In full scale, launching a lifeboat from a ramp with heights greater than those of existing installa tions is both impracticable and expensive.

• Model and full scale tests are normally documented by video recording.

Minimum instrumentation is accelerometers fore and aft and pressure measurements are limited to a few locations. Relating time history of accelerations and pressures to the trajectory of the lifeboat requires synchronization with a high-speed camera.

• Experiments are suitable to determine the actual loads on structure and people inside lifeboat, but they do not provide enough information necessary to improve the design. For this purpose, it is important to know the pressure and velocity distribution around the hull during water entry and the subsequent diving and re-surfacing of the lifeboat. g

p Fig:02 Time record of vertical acceleration expressed in multiples of gravity acceleration for the experiment and simulations at the front (left) and rear (right) of the lifeboat.

p Fig:03 Comparison of normalized maximum CAR-values for full load plus 10t of ballast for the three hull shapes obtained in experiment (blue) and in simulation (red) at the front (left) and rear (right) of the lifeboat.

t Fig:01 The original hull (top), modified aft body (middle) and modified aft body and bow (bottom).

In an environment as hostile as the North Sea, ensuring that lifeboats are available to be safely deployed in the event of an emergency isn’t just a luxury, but is vital for the continued operation of the Oil and Gas facility. During 2008 and early 2009 several Norwegian facilities were temporarily shut down, with consequent loss of millions of dollars of production, due to problems identified with lifeboats attached to the platforms.

❐ FACTS

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..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Marine

p Fig:04 Detail of the mesh structure in symmetry plane near hull and free surface, also showing position of the lifeboat 2s after launching.

p Fig:05 Distribution of pressure (upper) and velocity magnitude (lower) in symmetry plane around lifeboat 2s after launching (with wind).

p Fig:06 Distribution of pressure on hull surface 1.8s (left), 1.9s (middle) and 2s (right) after launching (with wind); also shown is the shape of free surface and the wetted hull area.

Recent advances in computational fluid dynamics (CFD) have made it possible to perform simulations of lifeboat launching at full scale and under realistic initial and boundary conditions. Simulations also allow an investigation of the effects of changes in hull shape without having to make a physical model. This makes it possible to investigate a larger range of hull shapes at a variety of launch conditions and finding a design that is acceptable for the expected use.

The method described here uses state-of-the-art CFD software coupled to a CAD design tool and a solver for 6 degrees-of-freedom motion of rigid bodies to efficiently evaluate the effects of both design changes and launching conditions on performance of lifeboats. The launching conditions that can be analyzed include wind, current, water depth and wave profiles in any combination. The flow and flow-induced motion of lifeboats (which are here considered to be rigid) is computed in a coupled manner. Since the number of necessary simulations in an optimization study is large, it is important that the method is computationally efficient. This requires local mesh refinement and an efficient handling of mesh adaptation to the position of lifeboat as it moves.

After trying several alternative approaches, the authors settled upon a method that employs overlapping grids, in which a background grid is adapted to the free surface and outside boundaries (such as the sea bed, oil platform or marine vessel), while the overlapping grid is attached to the lifeboat and moves with it without deformation. This overlapping grid method is applicable to unlimited motions (including overturning) and the boundary conditions (like wave generation) are easier to implement than in other approaches.

A lifeboat launched from a ramp undergoes three stages before it hits

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the water. First, it accelerates forward as it slides down the ramp under the influence of gravitational and frictional forces. As the center of gravity passes the edge of the ramp, the lifeboat will experience an angular acceleration due to the bow-down pitch moment from the reaction force at the edge of the ramp, acting behind the center of gravity. This pitch moment ceases when the rail of the lifeboat leaves the ramp. The lifeboat will then accelerate downwards with nearly constant horizontal and angular velocities before the impact with the water. During this third stage it is appropriate to start the coupled simulation of fluid flow and flow-induced motions. Initial conditions for simulations include position of the center of gravity relative to water surface and trim angle. Initial horizontal, vertical and angular velocities need also to be prescribed.

To gain confidence with this technique of simulation, a validation study was performed in collaboration with Norsafe AS to examine the effects of hull shape on forward motion of a lifeboat and accelerations experienced by the occupants. In this study, three different hull forms were considered: the original base form, modified aft body, and modified aft body and bow section.

The results of experiments and simulations for all three forms are presented in Figures 02 and 03. The results are both qualitatively and quantitatively sensible, reflecting the effects of design changes in the same way as the experiment.

The usual quantitative measure of acceleration is expressed as the so called CAR-value. For all three forms, the accelerations are higher in the rear than in the front part, but the difference reduces as more changes are carried out to the original design. Furthermore, the absolute level of the CAR-values is

..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Marine

The method described here uses state-of-the-art CFD software coupled to a CAD design tool and a solver for 6 degrees-of-freedom motion of rigid bodies to efficiently evaluate the effects of both design changes and launching conditions on performance of lifeboats.

Fig:07 u Predicted angular position (top), angular velocity (middle) and angular acceleration (lower) of the lifeboat during the first 6s after launching, for the no wind and wind condition.

reduced with each modification. The hull with modified aft body and bow leads to a reduction of CAR-values at the rear by 20% relative to the original design. The reduction of CAR-values in the front is significantly lower - of the order of 5%.

Calculations performed so far show that a simulation of lifeboat motion with three degrees of freedom (two linear and one rotation motion) in full size, from the time it is launched until it re-surfaces from water and moves about 40 m away from the launching point, can be performed on a single processor (i.e. a single core of a multicore processor) in less than a day using a grid made of about 300,000 control volumes.

Validations against tests performed in calm water indicate that this mesh resolution is sufficient to distinguish the effects of design changes. Final validations for optimal design may require finer meshes and the use of more processors to keep the run time of the same order (1 to 2 days). This makes the use of CFD for the investigation of loads onto lifeboat structure and accelerations to which people at different seats are exposed during water entry, an ideal supplement to experimental investigations, which can be limited to final validations of an optimized design. With a cluster of hundred processor units, it is possible to perform thousands of simulations and evaluate the results within just a few weeks. <

r The University of Agder is the fifth largest higher education institution in Norway. The university was established in 2007 when Agder University College officially became the University of Agder. Agder refers to the region, consisting of the two counties of Vest-Agder and Aust-Agder.

i MOREâ&#x20AC;&#x2C6;INFORMATION info@uk.cd-adapco.com

http://www.uia.no/en

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..::FEATURE ARTICLE Marine

q Fig:01 Borescope image of cavitation with (right) and without (left) vortex generators.

CHALLENGES + SOLUTIONS Hydrodynamic Aspects of Containership Propulsion Anne Boorsma, Patrick Fitzsimmons, Dejan Radosavljevic and Stewart Whitworth, Lloyd’s Register ODS Technical Investigations and Analysis Consultancy, UK.

r LLOYD’S Register is a risk management organisation providing risk assesment and risk mitigation solutions and management system certification around the world.

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Lloyd’s Register ODS has recently been involved with the investigation of a number of vibration and noise related habitability problems aboard feeder containerships of 2000-3000 TEU capacity having all-aft deckhouses; feeder containerships are relatively small vessels that transpor t cargoes to and from large, long-haul container terminals.

The effect of these vibrations range from unacceptable levels of noise and poor crew comfort through to sleep disturbance in the living quarters and damage to ships structures. Simply writing down the 13 mm/s peak level of vibration recorded on the bridge was a challenge!

Spectral analysis of the vibration signal confirmed that the source of the vibrations was not from the engine nor from ancillary machinery, but instead resulted from propeller cavitation; a function of the propeller inflow.

Lloyd’s Register ODS has been working actively on improving and validating methodologies for the prediction of propellerradiated hull pressures. Validation material is provided by means of propeller observations through a borescope and hull pressure measurements at ship scale. CFD simulation is used to improve the prediction of propeller inflows, i.e. ship wakes.

Extensive pressure and vibration measurements were performed by Lloyd’s Register ODS on behalf of the builder, while the images of cavitation were obtained as part of ongoing research within the Cooperative Research Ship (CRS), a joint-industry research body. To remedy the high vibration and noise levels, this ship was fitted with vortex generators to alter the inflow into the propeller causing a reduction in hull pressures radiated from the collapsing sheet and tip vortex cavitation on the propeller.

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Propeller analysis Experiments were carried out at model scale to examine the extent to which the hull’s wake influenced the pressure fluctuations generated by the propeller, which were responsible for the ship-wide vibrations. Analysis of the experimental results identified pressure pulses at the first and second blade passing frequencies, a phenomenon generally ascribed to sheet cavitation. Subsequent observations using a borescope showed that generous amounts of thick sheet cavitation grew and collapsed as each blade passed through the wake peak in the 12 o’clock position.

This propeller, shown in Figure 1, operated in an inflow field that, at model scale, exhibited a strong and highly retarded axial wake peak between the 10 o’clock and 2 o’clock positions.

Between the 10 o’clock and 12 o’clock position the propeller inflow angle increased, causing cavitation to grow. The subsequent decrease in inflow angle, between the 12 o’clock and 2 o’clock position, gave rise to a dynamic collapse of the cavitation volume.

The radiated pressure field is directly related to the dynamics of the cavity volume variation and thus the strongest contribution to the hull pressure pulse is generated during the dynamic collapse phases of on-blade and off-blade cavitation volumes.

As a remedy against the large radiated pressure from the collapse of substantial sheet-cavitation volumes, triangular fin-type

..::FEATURE ARTICLE Marine

p Fig:04 Comparison of computational and experimental axial wake.

p Fig:02 Axial wake turbulence model comparisons at full scale (top) and model scale (bottom).

p Fig:03 Axial wake with and without vortex generators at full scale (top) and model scale (bottom).

vortex generators were fitted to the hull several propeller diameters upstream of the propeller plane. Such devices are placed sufficiently far ahead of any region of retarded hull flow to promote mixing of the low-energy boundary-layer flow with the more energetic free stream flow. This inhibits flow retardation in the streamwise direction thus reducing the axial velocity deficit in the wake peak. The present devices halved hull pressure amplitudes at blade passing frequencies.

Subsequent video observations suggested that fitting of vortex generators had the desired effect in that the volume of the cavitation region were significantly reduced.

Inflow prediction The performance of a propeller is strongly dependent on the quality of the ship wake, i.e. the propeller in-flow. When the quality of the propeller inflow is poor and there are large variations in propeller inflow angle, cavitation will develop, which can cause significant pressure fluctuations. As we have seen, the addition of vortex generators can improve the ship wake and, correspondingly, reduce the pressure fluctuations that cause ship vibration.

The traditional method of studying propeller inflow wakes involves measuring the wake at model scale, without an operational propeller, and then using empirical methods to scale accordingly. Although successfully used many times in the past there are some shortcomings of this method, namely the scaling of axial inflow using empirical methods rather than computing from first principals, scaling of the axial wake component only and not the tangential component (a significant factor in the prediction of propeller cavitation) and the lack of hull-propeller interaction. CFD methods can be used to address all three of these shortcomings although in the current study the third will not be considered as no propeller is modelled.

CFD analysis was performed to predict the nominal wake of the feeder container ship travelling at 21.5kn with a draft of 11m using STAR-CCM+.

Calculations were performed at both ship scale and model scale with comparisons made between CFD results and model test data.

Three different turbulence models were evaluated for suitability to this type of study, namely the 1 equation Menter, k-ω SST and Reynolds Stress (RSM) models were used. Significant differences were observed between the results obtained using each of the different models, as shown in the wake contour plots presented in Figure 2. The result obtained using the k-ω SST model fails to predict the ‘hook’ shape commonly observed in wake profiles, the result obtained using RSM, however, is much closer to the experimental observations.

Comparisons between results and experiment at 60% of the propeller

radius show that of the three turbulence models the RSM shows the closest agreement to the experimental data. Accurate prediction of tangential and radial wake components is still difficult when using Reynolds Averaged Navier Stokes (RANS) type turbulence models, primarily due to the deficiencies of these turbulence models in predicting swirling flows. However, reasonable agreement with experiment is still attainable, as shown in Figure 4.

Measured ship scale wake data is rare, and none was available for this particular container ship. However, given that the techniques employed to predict wakes at ship scale are identical to those used at model scale, it is reasonable to assume that both sets of results will be of similar accuracy. Indeed, CFD wake analyses performed by Lloyd’s Register ODS for ships with available measured ship scale data have shown this to be the case. Large differences between full scale CFD results and those derived from the model tests results using empirical scaling factors were seen, which serves to emphasise the advantage of CFD over empirical methods. Such methods have been used extensively in the past but the increased accuracy of CFD wake predictions can now be utilised to provide better results.

One of the key advantages of CFD, not just in the marine industry, is the ability to visualise and analyse detailed flow features that would otherwise be unavailable. For example, the CFD results identified vortices above and below the propeller hub. The grid of measurement locations in an experiment would usually be too coarse to capture data behind such small-scale features.

As discussed earlier, vortex generators were placed upstream of the propeller to help reduce cavitation and the corresponding vibrations. The CFD results, seen in figure 3, show that at both model and ship scale, a more shallow wake peak is observed and, at ship scale, reduced velocities are seen throughout.

However, significant differences in the flow field are observed at model and ship scales. This is due to the relatively thinner boundary layer at full scale, which reduces the ability of the vortex generator to mix the higher velocity free stream flow into the boundary layer itself.

Conclusions Validation of the ability of CFD to accurately predict propeller inflow has so far been carried out at model scale. Lloyd’s Register ODS is currently working on ship scale propeller cavitation-characteristic predictions and, upon completion, it is expected that CFD will become the standard method for determining propeller inflows. The results demonstrate that the choice of turbulence model can greatly affect the accuracy of results and so further study is to be conducted looking at modified RANS models and DES methods for wake prediction.<

i MORE INFORMATION About Lloyds register please visit: http://www.lr.org

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..::FEATURE ARTICLE Turbomachinery

In the quest to improve efficiency and per formance of gas turbine engines, manufacturers over the past few decades have steadily altered their designs to increase turbine inlet air temperatures. Although this achieves the desired result, it produces the side effect of overheating the blades - and that leads to low cycle fatigue failures. But with oil prices fluctuating and the industry accepting the reality of the need to reduce carbon emissions, the tendency toward higher turbine inlet temperature continues unabated. This poses considerable challenges for the analysis and design of turbine cooling schemes.

To solve these issues, the used of Conjugate Heat Transfer (CHT) simulation amy be employed. This approach has been developed to permit the simultaneous modeling of heat transfers as well as the aerodynamic loadings on the vanes and blades and is gaining increasing acceptance and has been used by vendors such as General Electric, Honeywell, Pratt & Whitney and Solar Turbines (See Sidebar: Finding the Hot Spots).

What is CHT? Modeling production turbine blade designs is a daunting task. Not only is there the complexity of the blade shape itself, but also the hub, the shroud, and the internal cooling passages of the blades and shroud containing ribs and bleed holes. Similar challenges arise in modeling the airflow, which encompasses the primary gas flow past the blades, as well as any tip leakage and the flow of the coolant inside the blades and shroud. A third factor concerns the heat transfer coefficient at the internal and external surfaces of the blades. Finally, there are the stresses affecting the blades.

Given this complexity, two methods have been used to simplify the modeling process. One is to simplify the geometry and boundary flow conditions used in the model so fewer calculations are needed. While this makes the modeling easier, it suffers in terms of accuracy and the results must be experimentally validated.

The alternative is to separately model each of the elements – the internal flow paths, the external flow paths, the blade metal and the surface heat transfers. This certainly simplifies each of the individual steps involved, however, the data from each separate step must then be coordinated accurately with the data from each of the others. This gets complicated when you realize that, for example, the rate of surface heat transfer affects both the temperature of the metal and that of the gas.

CHT takes a different approach. Instead of running several distinct models and then combining them, it runs all models simultaneously. This results in more accurate data and reduces the need to run multiple simulations. When calculating the heat transfer at a given point, for instance, it takes the actual values for the gas flow, gas heat and metal heat at that location, for each step in time, rather than the operator having to input a set of assumptions for these figures.

To clarify this, let’s take a look at the workflow involved in using CHT. This same workflow can be utilized analyzing for steady-state flows, as well as for assessing thermal responses to transient conditions such as startups or changes in operating load.

Setting Up the Model The first step is to import the CAD geometry of the blade, shroud and hub into the Computational Fluid Dynamics (CFD) software. This includes the primary gas path and the blade internal cooling path.

Once imported, the CAD is, automatically tessellated ready for meshing. Next, any needed corrections made to address errors such as edge overlaps or voids between the cells. These corrections can be done using either automatic surface wrapping tools or with partial manual control. Since there will be a large number of corrections you will not be doing it on full manual. When modeling a Siemens Tornado power generation engine being maintained and retrofitted by the Wood Group, for example, 600,000 corrections were needed. A further step is to use the automatic topology detection tools to split the surfaces into three domains – the primary gas path, the internal gas paths and the blade solid. This also identifies the surfaces between each of the domains.

Once the surfaces are identified, volume meshes are created for both the fluid and solid domains. While it is possible to do this using just tetrahedrons, a better system is to agglomerate the tetrahedrons into arbitrary polyhedral cells, typically with 12-16 faces. These can be automatically generated and, since this leads to about about 2/3 fewer cells, calculations run much faster than when using just tetrahedrons while yielding the same fineness of resolution. In the case of the Tornado engine, the process of importing the CAD design making the surface corrections and generating the 10 million cell volume mesh took about 3 hours on a single processor.

Running the Calculations Once the meshes have been created, it is time to run the flow analyses with both heat transfer and stress. While CHT simulations are not new, being able to do it for an internally cooled turbine blade is new, because of the automated process of generating a continuous mesh in the fluid and solid regions. The flow is calculated using a Segregated pressure-based IMPLicit g

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..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Turbomachinery

Eliminating Heat Stress Failures in Industrial Turbines Drew Robb, freelance writer.

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..::FEATURE ARTICLE Turbomachinery

❐ FACTS Finding the Hot Spots

algorithm (SIMPLE) which is extended to deal with compressibility across the full subsonic to supersonic range. Heat transfer is calculated using an enthalpy transport equation that is seamlessly solved across the fluid and the solid domains. Since the fluids and solids have separate heat-transfer coefficients, a thermal diffusion coefficient is calculated for adjacent fluid and solid cells using a harmonic average of their individual heat-transfer coefficients. The flow and heat transfer analysis was run on a four-processor machine and took about 48 hours to compete.

The newest element in this process is to perform stress using a finite volume (FV) methodology using a segregated iterative solver. This method produces consistent results for different types of mesh, including polyhedra.

It also has the advantage of requiring about one-tenth the memory to store the core information compared to a typical finite element iterative solver with the same number of nodes. FV has several additional advantages over FEA including benefitting from full parallel scalability.

Test Results The flow and thermal model on the Tornado engine showed that the temperature stabilized around 500 iterations. Since the blade internal temperature is the primary factor in stress development, the solution was stopped after 1000 iterations. Slices of temperature taken throughout the blade and the fluid showed that there was some small cool down achieved by the internal cooling passages.

Plotting the cooling passage flow by itself, showed that the fluid increased to full temperature within a very short distance of entering at the bottom of the blade.

The thermal and stress analysis showed overheating and high stress resulting in deformation at one corner of the blade shroud end plate. This matched actual damage that was found on the turbine being overhauled.

As these tests illustrated, CHT has the potential to offer turbine manufacturers and aftermarket support firms a simpler, faster way to identify thermal stress problems. Rather than having to run a series of separate simulations, and then having to coordinate the results, running a CHT simulation speeds the design process and potential problems can be addressed before the parts are manufactured. <

i MORE INFORMATION VISIT: www.cd-adapco.com/applications/turbomachinery

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Solar Turbines Incorporated - a Caterpillar company headquartered in San Diego, California that manufactures small and medium-sized industrial gas turbines - used Conjugate Heat Transfer (CHT) to analyze the flow and thermal properties on a cooled C3X transonic turbine guide vane for a NASA under three different sets of operating conditions. The blades were cooled internally by ten round air pipes.

“In order to avoid blade failure caused by hot spots, we need to have very accurate prediction methods for metal temperature,” says Jiang Luo, Ph.D., a consulting aerospace engineer working in Solar Turbine’s aerothermal department.

Solar used CD-adapco’s STAR-CD software to create a 3.1 million cell model of the blade (0.7 million cells), the internal cooling air channels (1.0 million cells) and the external hot gas (1.4 million cells).

STAR-CD was selected since it offered the best accuracy for this type of model. Since the vane has a constant cross-section, a 38,000 cell, 2D mesh was made of the blade’s cross section, and these layers were then stacked into a 3D model.

“The accuracy of the prediction is depended on the heat transfer coefficients (HTC) near the surface, both inside and outside,” says Luo. “In the traditional decoupled method, you specify the HTC on the surface without computing it directly.

But with this new method, we have a model that includes the outside hot gas, the inside coolant and also the metal.”

Solar ran the simulations and found that the results were within 3% of previously measured temperature data.

“Right now many companies are still relying on rig tests or engine tests to fine tune their cooling scheme design to eliminate hot spots,” says Luo. “CHT has the potential to accurately predict hot spots earlier in the design process.”

• STAR-CCM+

• STAR-CAD Series

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For more information: info@uk.cd-adapco.com www.cd-adapco.com/energy

3

Expertise

..::WINNERS Calendar Competition

calendar competition Profiling THE best 2009 CALENDAR competition entries

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..::WINNERS Calendar Competition

After an exhaustive two month search, CD-adapco announced the winner of the 2009 Calendar Competition. For the third year running, the competition has given users of CD-adapco software the chance to showcase their post-processing skills by producing striking images of their work.

Stephen Ferguson, CD-adapco’s Head of Marketing Communications, explains: “Post processing CAE results is no longer about just getting numbers out of a simulation, but also being able to engage and inform colleagues from other disciplines about an analysis’ effectiveness. The quality of this year’s entries has once again impressed everyone at CD-adapco and has shown just how skilful our users are in effectively deploying our software across a range of different applications. With over 40 entries to choose from, all of an exceedingly high standard, selecting a winner was extremely hard and is a reflection of both the high levels of skill shown by our users as well as the ease of use of our products.”

With such a wide selection of images to choose from, finding a winner was always going to be tough but one image stood out with Roberto Di Francesco from Innovazione getting the most votes from the CD-adapco judges.

Choosing an Asus Eee PC 900 ultra portable laptop as his prize, Roberto was clearly delighted that his image, Aerodynamic analysis of a sport touring motorcycle, was chosen as the winner “We are very happy to have won the competition and to have our work appreciated by our friends at CD-adapco.”

Adorned with stunning imagery, this elegant desktop calendar celebrates the world of CAE through visually impressive simulation results, covering everything from ship’s propellers to domestic kitchen ovens, from UFOs to gas masks. Each image was submitted by a CD-adapco customer as part of the 2009 CAE Guru competition, and selected by a panel of CD-adapco judges.

“The ability to communicate engineering information, while engaging with an increasingly non-specialist audience, is a key skill for any CAE analyst”, says CD-adapco’s Marketing Communication Manager Stephen Ferguson. “The images in this calendar demonstrate that, although people are becoming increasingly familiar with simulation generated imagery, a carefully generated CAE image still has the power to captivate.”

Claim Your FREE 2009 CD-adapco CAE Calendar We still have calendars available if you haven’t already received one, please visit: www.cd-adapco.com/press_room/2009/01-12-calendar/ to claim yours now.

If you fancy your chances as next year’s grand prize winner, the competition opens from October 2009 and will again feature prizes for the twelve best entries, this year we gave away USB memory sticks for every successful entry. Subscribe online for e-dynamics for our monthly newsletter which will keep you posted on all the competition details as well as our other events: http://www.cd-adapco.com/edynamics

i TO CLAIM YOUR CALENDAR Visit: www.cd-adapco.com/press_room/2009/01-12-calendar/

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..::REGULARS Dr Mesh

Welcome to the ParT-y DR Mesh, CD-adapco.

There are cer tain things that I simply hate doing; ironing, shopping with Mrs Mesh, mowing the lawn, oh and re-organizing impor ted CAD geometry. There isnâ&#x20AC;&#x2122;t a whole lot the folks at CD-adapco towers can do about the first three but the clever STAR-CCM+ developers have been working hard to make the final one less of a chore.

You may have noticed that in STAR-CCM+ 3.06 you could import your native cad files (unigraphics NX, Solidworks etc) well in 4.02 this is taken one step further and the structure of the original CAD is also retained in the form of PARTS. The old structure of STAR-CCM+ is all still there with continua and regions so you can work in the same way you always have, but Parts is introduced as a level above to help organise your model in an easier, faster and more efficient manner. So lets look at an example.

your CAD PART 1 - Grabwe will bring in our

ays First off, as alw going this case I am CAD model, in ks on dis ke bra the of to look at one CAD the rt po . We im the mesh-mobile assembly prt, the NX an as assembly rts as the file impo ll notice is that w region ne first thing you wi a ng ati cre option of In you are given the as a new part. y as before) or it e os ch ll (in the same wa wi d nt the latter an this case we wa accordingly.

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it out PART 2 - Sort is imported you will be

bly Once your assem der and see all the geometry fol able to expand ssemblies and b-a su emblies, your different ass as in the CAD y in the same wa rry parts, all named ger have to wo lon no u yo t ing tha nfused. co g geometry mean ttin ge d an everything about re-naming

..::FEATURE ARTICLE Dr Mesh

PART 3 - Contact!

to these parts is that I need Now the problem with all and where my interfaces t wha hing touc is t wha work out R-CCM+ is clever enough should be....NOT SO! STA contact with each other so in are s to find out which part s into regions (more on part r when you come to turn you you. So to work out the for y read all are es rfac that later) your inte and select “Find parts you want, right click contacts, just select all the R-CCM+ will STA king thin of bit little a r Part/Part Contacts....”. Afte on. e can mov tell you it is done and you

ing gift PART 5 - PARTall your regions are created you

Once normal. d solve them as can then mesh an y help is ma t tha ts hin tra A couple of ex Region w turn on “Perthat you can no ntinua, co sh me your to meshing” in no longer have u yo t tha meaning continua for ing sh me t en setup a differ jects you have thin ob meshing. Also if there etc s ne va non-contiguous ide gu tal, heat sinks, ate such as sheet me automatically cre object mesher to n . thi the w no is ratio geometries t ec asp h hig es for prism only mesh

PART 4 - Tota lly

regionable...

With all my co ntacts found, I can then go ah parts into region ead and turn my s. In this case we want to convert but you don’t ha all our parts ve to if you don’t want to, you can selection of parts just change a into regions if req uired.

So with the parts selected again all you do is right “Set Region” an click, select d then either ch oose an existing this case, hit “n region or, as in ew”. If you choo se to create new your parts then regions from you will be ask ed how you wo regions, bounda uld like your ries and feature curves split. On chosen the right ce you have option everything else is done for you, easy eh!

So what are you waiting for PARTake in this exciting new PARTicular feature and you can join the PARTy, sorry no more puns I promise (PARTly).

i SEND ME YOUR THOUGHTS & SUGGESTIONS FOR FUTURE DR. MESH ARTICLES: dr.mesh@uk.cd-adapco.com

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..::REGULARS Training

TRAINING VENUES Detroit, United States Houston, United States Seattle, United States London, United Kingdom Nürnberg, Germany Paris, France Turin, Italy Bangalore, India

TRAINING Training adds incredible value to the software you have purchased and comes highly recommended by all. Courses are regularly held at CD-adapco offices around the world including: Detroit, Houston, Seattle, London, Nürnburg, Paris, Turin and others.

The courses listed on our website can be scheduled to suit your requirements. To take advantage of this, please request information from your local training administrator.

View your local course offerings, customer testimonials and register for an upcoming course at: www.cd-adapco.com/training.

To Register for a Course: Complete the online registration (www.cd-adapco.com/training) or request a faxable form from your training administrator: USA: training@us.cd-adapco.com (+1) 734 453 2100 UK: info@uk.cd-adapco.com (+44) 020 7471 6200 Germany: training@de.cd-adapco.com (+49) 911 946433 France: info@fr.cd-adapco.com (+33) 141 837560 Italy: info@it.cd-adapco.com (+39) 011 562 2194 Choose from Courses Including: • Foundation Training • STAR-CCM+ Foundation • STAR-CD Foundation • STAR-Design • Advanced STAR-CCM+ • Advanced STAR-CD

• • • • • •

Advanced Meshing Advanced Modeling User Subroutines Spray & Combustion E2P Virtual Tow Tank

• Effective Heat Transfer • Simulation of Rigid Body Motion for Engineering Analysis • Engineering Process Automation through JAVA Scripting AND MORE...

Specialized Courses: New specialized courses relating to application specific areas are developed throughout the year. Check for these courses at: www.cd-adapco.com/training STAR-Tutor Online Training: STAR-Tutor is a virtual classroom that enables you to learn more about CFD and CD-adapco’s solutions, wherever you are. Whether you are new to CFD, using simulation in a new application area, or picking up a CD-adapco tool for the first time, STAR-Tutor can get you up to speed, fast. STAR-Tutor’s innovative format allows you to fit personal development training around your schedule. To view the STAR-Tutor schedule and course list, please visit: http://www.cd-adapco.com/training/STAR-Tutor/ Note: In most situations it will be possible to register trainees on the course of their choice. However, if requests for places on courses are received too close to the course date, this may not be possible. Availability of places can be obtained by contacting your local office. See our website for most up to date

schedules and registration. www.cd-adapco.com/training

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..::REGULARS Events

STAR Conferences CD-adapco organizes annual STAR Conferences to give users of STAR-CD, STAR-CCM+ and the STAR-CAD Series the opportunity to meet CD-adapco staff and other users.

The meetings usually contain presentations from our clients, as well as demonstrations of the latest developments in CFD and a chance to trial the latest offerings from our hardware and software partners.

REGISTER: http://www.cd-adapco.com/events/conference

Events

Integrate. Automate. Innovate. flow • thermal • stress

CD-adapco regularly participates in many global trade shows. To get the chance to talk in person with our experienced and friendly representatives, please make a note of our appearances at the confirmed shows below. For more information please contact our events staff: North America: Tara Firenze tara.firenze@us.cd-adapco.com Europe: Marianne Mueller marianne.mueller@de.cd-adapco.com North America ASEE Northeast Section Regional Conference April 3-4, 2009 Bridgeport, CT ASNE Day 2009 (American Society of Naval Engineers) April 8-9, 2009 Oxon Hill, MD CRAY’s IMEM April 19, 2009 Detroit, MI SAE World Congress 2009 April 20-23, 2009 Detroit, MI COE 2009 Annual PLM Conference & TechniFair April 20-22, 2009 Seattle, WA OTC May 4-7, 2009 Houston, TX Electric Power May 12-14, 2009 Rosemont, IL ASME Turbo Expo June 9-11, 2009 Orlando, FL AUVSI’s Unmanned Systems North America 2009 August 10-13, 2009 Washington, DC Coal-Gen 2009 August 19-21, 2009 Charlotte, NC 38th Turbomachinery Symposium September 15-17, 2009 Houston, TX 2009 SAE/IMechE VTMS September 29-30, 2009 Phoenix, AZ SPE Annual Tech Conference & Exhibition October 4-7, 2009 New Orleans, LA

SAE 2009 Commercial Vehicle Engineering October 6-8, 2009 Rosemont, IL SNAME Maritime Technology Conf. & Expo October 21-23, 2009 Providence, RI Fuel Cell Seminar November 16-19, 2009 Palm Springs, CA Power-Gen 2009 December 8-10, 2009 Las Vegas, NV

Dassault PLM Forum 2009 June 18-19, 2009 Mannheim, Germany VDI Erprobung und Simulation in der Fahrzeugentwicklung 24-25 June, 2009 Würzburg, Germany EUCASS 06-09 July, 2009 Paris, France Offshore Europe September 8-11, 2009 Aberdeen, UK

Europe OMC 2009 March 25-27, 2009 Ravenna, Italy CAEvolution Technologietage March 26, 2009 München, Germany Rina Superyacht Confernce April 01-02, 2009 Genoa, Italy Hannover Messe April 20-24, 2009 Hannover, Germany ACHEMA 2009 May 11-15, 2009 Frankfurt, Germany All Energy May 20-21, 2009 Aberdeen, UK Power Gen Europe May 26-28, 2009 Köln, Germany Nafems World Congress June 16-19, 2009 Greece Engine Expo June 16-18, 2009 Stuttgart, Germany

ASIA ICAPP ‘09 May 10-14, 2009 Tokyo, Japan STAR Conferences STAR European Conference 2009 March 23-25, 2009 London, UK STAR Russian Conference 2009 May 26-27, 2009 Nizhny Novgorod State University STAR Korean Conference 2009 June 8-9, 2009 Location TBC STAR Japanese Conference 2009 June 10-11, 2009 Location TBC STAR Chinese Conference 2009 June 15-16, 2009 Location TBC STAR American Conference 2009 June 22-23, 2009 Dearborn, MI STAR Konferenz Deutschland 2009 November 9-10, 2009 Berlin

i FOR MORE INFORMATION ON OUR EVENTS: http://www.cd-adapco.com/events/

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