Dynamics Magazine 302 by CD-adapco

issue 3.02

ENGINEERING SUCCESS

Features

AEROSPACE UAV’s Close Formation Flight

SPORT AUTOMOTIVE BUILDING Bicycle Wheel Aerodynamics World’s Sexiest Electric Car Personal Ventilation Systems

contents Introduction 03 Engineering Success Introduction by David L Vaughn 05

Breaking News • Java™ Hut • Microsoft

Wilson Football Simulation - Cover Story

STAR-CCM+ & Abaqus FEA co-simulation

13 Power-On-Demand AUTOMOTIVE 15 Suzuki Aerodynamics & air-cooling performance 19

Heat Transfer Turning the lights on

Le Mans Prototype Increasing Front Downforce

Battery Design STAR-CCM+ Battery Simulation Module

Aerospace 27 Close Formation Flight Unmanned aerial vehicles take to the skies SPORT 31 Bicycle Wheel Aerodynamics: Increasing workflow productivity with STAR-CCM+ & FieldView BUILDING SERVICES 35 Feel an Open Window Anywhere Personal air ventilation systems INDUSTRIAL & COMMERCIAL APPLICATIONS 39 Flowserve Optimization of Flow Coefficients for Large Control Valves ENERGY 42 Energy Giant Revolutionary wind turbine design 43

A Solar Powered Future Qualitative leap in renewable energy with STAR-CCM+

OIL & GAS 45 The Deeper You Go... Improving deep subsea oil & gas drilling performance Marine 49 Extreme Weight Lifting Resistance Calculation for SeaMetric Twin Marine Lifter 53

RANS Simulation Complex marine flow problems

Regulars 57 Training 58 Global Events

Global offices CD-adapco

Cover Image: Wilson football simulated in STAR-CCM+ (page 22)

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 Assistant Editor Associate Editors Art Direction & Design E-Dynamics Advertising Sales US Events European Events

Stephen Ferguson - stephen.ferguson@uk.cd-adapco.com Deborah Saban - deborah.saban@uk.cd-adapco.com Prashanth Shankara - prashanth.shankara@us.cd-adapco.com Lauren Gautier - lauren.gautier@us.cd-adapco.com Brandon Botha - brandon.botha@uk.cd-adapco.com Chris Dunne - chris.dunne@uk.cd-adapco.com Geri Jackman - geri.jackman@uk.cd-adapco.com Tara Firenze - tara.firenze@us.cd-adapco.com Sandra Maureder - sandra.maureder@uk.cd-adapco.com

Subscriptions & DIGITAL EDITIONS Dynamics is published approximately twice a year, and distributed internationally. All recent editions of Dynamics, Special Reports & Digital Reports are now available online: http://www.cd-adapco.com/press_room/dynamics We also produce our monthly e-Dynamics which are available on subscription. To subscribe or unsubscribe to Dynamics and e-Dynamics, please email info@uk.cd-adapco.com To advertise in Dynamics magazine or e-Dynamics, please download our media kit online: www.cd-adapco.com/products/brochures/dynamics/mediakit.pdf IN LOVING MEMORY - THIS ISSUE IS DEDICATED TO IBRAHIM CD-adapco is mourning the death of Ibrahim Hadžić, a member of the development team in Nuremberg office, who died at the age of 42 on September 27, 2010. He has fought a battle against pancreatic and liver cancer since October 2009, but unfortunately neither the two surgeries nor the chemo-therapy helped. Ibrahim - whom friends called Ibro - never gave up and worked on his tasks through this difficult period until the end of July. We will always remember him for who he was: a dedicated scientist, a loyal employee, a great colleague and a good man in every respect...

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

Resellers

Russia SAROV info@saec.ru South Africa Aerotherm Computational Dynamics martin@aerothermcd.co.za Turkey A-Ztech Ltd info@a-ztech.com.tr

Resellers

Australia Veta Pty info@veta.com.au Greece ENEFEL enefel@enefel.gr Israel ADCOM info@adcomsim.co.il New Zealand Matrix Applied Computing Ltd. sales@matrix.co.nz

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

..::INTRODUCTION Engineering Success

We ensure our customers remain successful with engineering services that provide them with facilitated transfer of technology, burst capacity resources and custom software tools.

Engineering Success Introduction by David L Vaughn CD-adapco’s principal aim is “Engineering Success”: to help our customers to succeed through the application of engineering simulation, driving innovation in their products AND reducing the engineering time and cost associated with bringing those products to market. In its most fundamental form, success works on a personal level, ensuring that individual engineers are able to deliver meaningful simulation results on time and in a manner which can be used to influence the design process.

The articles in this magazine detail just a few examples of the many success stories that we encounter every day. I hope that as you read them, you will be inspired to consider your own application areas, and the ways in which we can help you to be even more successful in the future.

Because CD-adapco was founded by, and is almost entirely staffed by, simulation engineers, we are uniquely placed to understand the challenges faced by you every day. Having walked in the same shoes, we understand the importance of ensuring our software products are accurate, efficient and easy to use.

Enjoy your read.

We also recognize that the path to success is not always a smooth one. We are committed to providing excellent dedicated software support. Engineers are tasked with understanding your processes and issues, and are on-hand at any time to ensure that you are using our software in the most effective and efficient way.

David L Vaughn VP Worldwide Marketing CD-adapco

We ensure our customers remain successful with engineering services that provide them with facilitated transfer of technology, burst capacity resources and custom software tools.

i FOR MORE INFORMATION PLEASE EMAIL: dvaughn@us.cd-adapco.com

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..::INTRODUCTION Breaking News

Welcome to the JAVA™ Hut: a community application exchange for STAR-CCM+ CD-adapco announces JAVA™ Hut, the über-cool way for users to enhance productivity and automate engineering processes with STAR-CCM+. “It’s a community thing,” says Stephen McIlwain, CD-adapco’s Director of Support. “We are constantly surprised by the degree of innovation that our users bring to STAR-CCM+, often writing macros and scripts that enhance STAR-CCM+ in ways that we never would have imagined. JAVA™ Hut fosters this collaboration and communication among the CD-adapco user community for those wishing to extend their use of STAR-CCM+ by sharing and downloading Java™ scripts.” Using the modern software architecture of Java™, engineers using STAR-CCM+ in their engineering processes are further enhancing the potential of the code by scripting JAVA™ applications that link directly into the STAR-CCM+ suite. The Java™ apps are being used to deeply integrate STAR-CCM+ directly into engineering processes, to provide fully automated CAE simulation suites, extend applicability of the toolset into new areas, and link directly to other CAE tools. The intention of JAVA™ Hut (http://javahut.cd-adapco.com) is to provide a collection point for STAR-CCM+ users to share JAVA™ scripts which they

have developed for STAR-CCM+ and also download Java™ scripts from other users that they might find helpful in their analyses. CD-adapco also provides a forum for users to rate the usefulness of the application, provide feedback for the author and suggest possible enhancements. “With new developments in technology and social networking, CD-adapco stays in the forefront of the CAE industry by offering its customers tools to enhance productivity and to get the most from STAR-CCM+,” explains McIlwain. “It is extremely important that we continue to create new methods for our customers to be successful and get even more out of one of the world’s best CFD codes. JAVA™ Hut is just another way for us to do this.” JAVA™ Hut is now available for CD-adapco customers to use.

i MORE INFORMATION http://javahut.cd-adapco.com

Release of STAR-CCM+ V5 heralds new strategic partnership for CD-adapco & Microsoft CD-adapco is strengthening its relationship with Microsoft through tighter support with the Microsoft Operating Systems, Windows 7 and Windows HPC Server 2008, and the integration of STAR-View+ into the Microsoft Office 2010 suite of products. STAR-CCM+ V5.02 was the first release of CD-adapco’s flagship product to be ported directly onto Microsoft Windows 7, giving the industrial community direct access to multidisciplinary engineering simulation from the comfort of this new operating system. Joined efforts between the two companies are underway to incorporate Windows 7 light-up features in STAR-CCM+. For compute-intensive simulations performed over a cluster of Windows computers using Windows HPC Server 2008, STAR-CCM+ will be tightly linked to the job scheduling features, compute node management features and image deployment capabilities. Commenting on the strategic partnership, Jean-Claude Ercolanelli, CD-adapco’s VP Product Management, said: “CD-adapco has been working closely together with Microsoft for many years. The releases of Windows 7 and STAR-CCM+ V5 have given us the perfect opportunity to cement this relationship further. The new fruit of our partnership is the direct inclusion of STAR-View+ into Microsoft Office 2007 and MS Office 2010. This enables our users to distribute their simulation results interactively using MS Word, PowerPoint and Excel: enhancing collaboration between engineering teams by giving everyone access to interactive visualization of simulation results.” Greg Kirchoff, Director of Vertical Global ISVs at Microsoft, added, “Engineering customers want desktop applications to work seamlessly

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with their simulation models so we’re very excited about the STAR-CCM+ announcement around Windows 7 and Office 2010.” STAR-CCM+ 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 well as show and hide features within the scene.

i MORE INFORMATION www.microsoft.com/windows/windows-7

..::INTRODUCTION Breaking News

ADVANTAGES OF ENSIGHT CFD

Large graphics space, easy to use interface, simple calculator for key computation values, startup wizard to simplify workflow We surveyed the market and found out that you need a better CFD post-processor. Using the same highquality graphics and rendering engine of EnSight 9, we created a new product specifically tailored to CFD users. The interface is simple and focused, designed to allow you to explore your data interactively. With EnSight CFD, you will be more effective in analyzing, visualizing, and communicating simulation results to your team. Feature List Read, explore and plot data Rotate, pan and zoom Simple calculator Create isosurfaces, boundary layers, vortex cores, separate/attach lines, and shock surfaces Create particle traces, transient particle traces/pathlines and surface restricted traces

Add annotations Export movies and 3D models Print and save images 32-bit and 64-bit compatible Floating and node-locked licenses Web, email, phone support Windows, Mac OS X, Linux compatible

Directly import STAR-CD .ccm/.ccmg/.ccmp/.ccmt files www.ensightcfd.com 06 dynamics ISSUE 3.01

..::INTRODUCTION Wilson Ball Simulation

Advanced Aerodynamics Simulation of Championship Balls Wilson Sporting Goods Co. Teams with CD-adapco Wilson is taking its soccer balls to the next level in aerodynamics research using CD-adapco’s STAR-CCM+ software on Windows HPC Server 2008. While the attention of the world focused on soccer balls (or footballs if you prefer) this summer, Wilson continues to drive technical innovation in the design of their sports balls by teaming with CD-adapco to redefine state-of-the-art computer simulation of soccer ball aerodynamics. During preparations and all the way through the final match of this year’s World Cup, FIFA fielded complaints from many players concerned with uncontrollable speed and/or unpredictable flight behavior of the official match ball which was developed and manufactured by the tournament’s primary corporate sponsor. The primary objective of this partnership is to ensure that Wilson maintains its competitive edge in the technical design of its products with a focus on ball aerodynamics. “Wilson has long realized the importance of aerodynamics in the design of reliable and high performance golf balls, footballs, soccer balls, basketballs, and baseballs,” said Doug Guenther, Wilson Sporting Goods Co., Vice President of Research and Development. “Several factors lead to the choice of CD-adapco and STAR-CCM+,” stated Guenther. “The ability of STAR-CCM+ to accurately and efficiently solve unsteady flows with boundary layer transition was certainly a key technical factor, but equally important is the support and flexibility offered by CD-adapco. Their dedicated support model and Power-on-Demand offering is an ideal solution for our needs.” The complexities with computational simulation to analyze the flow around soccer balls are well documented. In the past, most computational fluid dynamics (CFD) studies were limited to fundamental models. g

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..::INTRODUCTION Wilson Ball Simulation

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..::INTRODUCTION Wilson Ball Simulation

This was accomplished by simplifying the details in the shape of the ball and ultimately reducing the actual flow physics involved. These simplifications eventually led to inaccurate results, forcing ball designers to perform expensive and time consuming wind tunnel tests. STAR-CCM+ is CD-adapco’s flagship software product which allows engineers to accurately and efficiently simulate aerodynamics (and other types of fluid flow) of any level of complexity using CFD. Using STAR-CCM+ allows Wilson to easily model the genuine shape of the ball including details such as the panels, seams and stitches. This is imperative because these geometric details affect the transition of the airflow from laminar to turbulent, and this is the critical element to accurately predicting the aerodynamic drag and stability of the ball. The initial phases of the project were executed using Power-on-Demand with computer clusters running Windows HPC Server 2008. The Power-on-Demand offering from CD-adapco enables Wilson to take advantage of cloud computing when executing STAR-CCM+ simulations. “Cloud computing is a fantastic cost-effective solution for Wilson, and our Power-on-Demand offering makes it easy to use STAR-CCM+ on the cloud.” said David L. Vaughn, VP Worldwide Marketing for CD-adapco. Vaughn continued, “We are proud to partner with Wilson, not only because of their renowned history of quality products, but because of their innovative vision that includes applying technology to continue providing the best equipment to the world of sports.” Wilson and CD-adapco intend to follow the success of this project with studies focusing on other Wilson Sport categories, including American footballs. <

i FOR MORE INFORMATION ON WILSON, PLEASE VISIT www.wilson.com/

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..::INTRODUCTION Wilson Ball Simulation

About CD-adapco CD-adapco is the world’s largest independent CFD focused CAE provider. Our core products are the technology-leading simulation packages, STAR-CCM+ and STAR-CD. The scope of activities, however, extends well beyond CFD software development to encompass a wide range of CAE engineering services in fluid dynamics, heat transfer and structural engineering with an ongoing mission to “inspire innovation and reduce costs through the application of engineering simulation software and services.” A privately owned company, CD-adapco has maintained 16% organic year-on-year growth over the last 5 years. CD-adapco employs over 400 talented individuals, working at 21 different offices across the globe.

About Wilson Chicago-based Wilson Sporting Goods Co., a division of Amer Sports, is one of the world’s leading manufacturers of sports equipment. The company designs, manufactures and distributes advanced equipment that helps players improve their performance. Wilson’s core categories include Baseball, Football, Basketball, Softball, Bats, Volleyball, Soccer, Youth Sports, Uniforms/Apparel, Golf, Footwear, and Racquet Sports (Tennis, Racquetball, Squash, Badminton and Platform Tennis).

Wilson has long realized the importance of aerodynamics in the design of reliable and high performance golf balls, footballs, soccer balls, basketballs, and baseballs. Doug Guenther, Wilson Sporting Goods Co. Vice President of Research & Development

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..::INTRODUCTION STAR-CCM+ & Abaqus FEA

SIMULIA is the Dassault SystĂŠmes brand that delivers a scalable portfolio of Realistic Simulation solutions. This includes the Abaqus product suite for Unified Finite Element Analysis, multiphysics solutions for insight into challenging engineering problems, and SIMULIA SLM for managing simulation data, processes, and intellectual property. By building on established technology, respected quality, and superior customer service, SIMULIA makes realistic simulation an integral business practice that improves product performance, reduces physical prototypes, and drives innovation. Headquartered in Providence, RI, USA, SIMULIA provides sales, services, and support through a global network of regional offices and distributors. www.simulia.com

ABOVE

Co-simulation is the most practical and accurate method of solving aerodynamic flutter problems

STAR-CCM+ & Abaqus FEA co-simulation makes seamless fluid-structure interaction a reality By working closely with SIMULIA, we have managed to create a tool that, for the first time, brings best-in-class coupled fluid-structure interaction within the reach of a typical engineer. CD-adapco Senior VP of Operations, Dr. Bill Clark

i MOREâ&#x20AC;&#x2C6;INFORMATION VISIT www.cd-adapco.com/press_room

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..::INTRODUCTION STAR-CCM+ & Abaqus FEA

CD-adapco is pleased to announce that its industry leading simulation tool, STAR-CCM+, now includes a direct link to Abaqus FEA from SIMULIA, delivering fully coupled, two-way, fluid-structure interaction (FSI). From the bending of a tree’s branch in the wind to the flutter of an aircraft wing as it crosses the Atlantic, fluids and solids interact in harmony everywhere in the real world. However, in the virtual world of engineering simulation, the picture has rarely been quite so harmonious. Structural analysis and fluid dynamics, although intrinsically linked, have long been quite separate disciplines with the interaction between deforming structures and flowing fluids only being considered at a most basic level. The first products available for FSI simulations were often prohibitively expensive, in terms of computer resources and timescales, and relied upon third-party inter-code communication that had to be specifically configured for each new scenario. For these reasons, the numerical simulation of FSI problems has traditionally been the preserve of research projects and academic studies, operating outside of the main engineering design process. Not anymore. For the first time, CD-adapco’s industry leading simulation tool, STAR-CCM+, will have a direct link to Abaqus FEA, delivering fully coupled, two-way, fluid-structure interaction. Using direct co-simulation coupling provides efficiency and reduced overhead associated with things such as data transfer through file exchanges or use of external middleware software. This will make coupled fluid-structure-thermal calculations a regular part of the engineering design process. “This direct co-simulation coupling is possible because of the strong partnership between CD-adapco and SIMULIA,” said CD-adapco Senior VP of Operations Dr. Bill Clark. “By working closely with SIMULIA, we have managed to create a tool that, for the first time, brings best-in-class coupled fluid-structure interaction within the reach of a typical engineer.” “Our partnership with CD-adapco is a key part of our commitment to provide our mutual customers with a coupled multiphysics solution that helps them gain deeper understanding of their products’ real-world product behavior earlier in their development cycle,” stated Steve Levine, Chief Strategy Officer, SIMULIA, Dassault Systèmes. “SIMULIA is committed to developing new and improved direct co-simulation solutions that enable our valued partners such as CD-adapco to help their customers reduce time and costs of delivering high quality products to market.”

CD-adapco’s partnership with SIMULIA also means that setting up and running the problem may all be done within the easy-to-use STAR-CCM+ environment, with no need for writing scripts and input files or mapping data. Simply point STAR-CCM+ at the Abaqus FEA job you want to run and press “Go.” The powerful physics of both codes may be leveraged in coupled FSI with STAR-CCM+’s full range of available models, providing the ability to study coupled, single and multiphase flows, chemical reaction and combustion as well as flow regimes from low speed to hypersonic. The options available in Abaqus are similarly broad, with coupled simulation supported for static stress/displacement, dynamics (implicit and explicit), heat transfer, temperature-displacement, thermal-electrical and piezoelectric analysis. Put simply, the close-coupling between STAR-CCM+ and Abaqus brings the solution of a wide range of FSI problems within the easy reach of a typical engineer. In terms of both practicality and accuracy, co-simulation (in which both codes exchange data as they simultaneously run) is the only way to tackle problems such as aerodynamic flutter, fluid induced bending, vortex induced vibration and galloping. <

BELOW

Abaqus FEA and STAR-CCM+ co-simulation can be used to solve problems such as tire aquaplaning.

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..::INTRODUCTION Power-On-Demand

The compelling benefits of STAR-CCM+ / Power-on-Demand include: Increased Power: Each license allows access to unlimited computing resources, either on your own cluster or using those of cloud computing services Increased Throughput: Each license allows to run an uncounted number of sessions, concurrently or not Increased Flexibility: Creation of a flexible simulation environment that expands and contracts based on your workload and target performance parameters, providing you with burst capacity

Power-on-Demand: Engineering Simulation in the Cloud In the past thirty years, engineering simulation has evolved beyond all recognition. Once a speculative “Research and Development Tool,” simulation now plays a constant and critical role in almost any product development, generating a constant stream of engineering data that leads the design process. Once the sole domain of PhD-qualified academics, today’s simulations are as likely to be carried out by application engineers and designers as they are by simulation specialists.

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..::INTRODUCTION Power-On-Demand

Perhaps most importantly of all, everyone now has access to “super-computer” technology. Even the most humble of laptops now contain a multi-core processor, while serious engineering simulations can routinely use hundreds, if not thousands, of computer cores at a time. Using client-server software, an engineer can, with a simple laptop, monitor the results of an engineering simulation running on hundreds of cores on a computer cluster than might be physically located on a different continent. However, when it comes to the licensing of simulation software, the more things change, the more they stay the same. Since the very start, users of Computer Aided Engineering (CAE) software have been bound by inflexible annual licensing schemes that take no account of the cyclical nature of simulation demand experienced by a typical enterprise. Each year, users were forced to buy a certain number of “seats” (the number of instances of the software that can be run at one time) and limited to a set number of computer processors that could be run simultaneously. During times of peak demand, users were forced to fight over the same software and hardware resources that often remained unused during less busy times. Until recently, the number of software licenses that a company purchased was determined almost entirely by the extent of the hardware resources to which they had access. Users purchased (or long term leased) an expensive mainframe computer, with as many processors and as much memory as they could afford, and then simply bought a big enough software license to keep that computer number crunching for as many hours a week as possible. If the simulation workload outgrew the number-crunching ability of the machine, the only option would be to purchase a new, bigger computer and additional software licenses to match.

Burst Capacity With little prospect of being allowed to purchase a new super-computer every time demand temporarily increased, users were usually stuck with a fixed number of “software seats,” independent of demand. This often posed some difficult problems: What happens if your company suddenly wins an unexpectedly large short term contract that will push your current simulation capacity beyond its limit? What happens in the weeks before a design freeze, when the whole engineering department is frantically demanding simulation data, and spare computer processors and unused software licenses are rarer than gold dust? What happens, a few weeks later, during vacation time, when demand for simulation results is down, and computers and software licenses lie idle? What has been missing from the traditional license model is a “burst capacity” allowing users to scale up their software usage during busy periods and then scale it back down as necessary. With this in mind, in April 2010, CD-adapco introduced a Real Time Licensing scheme for their flagship STAR-CCM+ engineering simulation tool. Real Time Licensing The “Power-on-Demand” license allows users to access unlimited computational resources for a single hourly fixed fee, breaking the relationship between license cost and computer resources (number of cores) used for a simulation. Rather than purchasing STAR-CCM+ licenses “by the seat” or “by the processor,” Power-on-Demand allows users to purchase licenses “by the hour.” For example, a five hundred hour license would allow you to run as many simulations as you could set up, using as many processors as you have access to, for a period of up to five hundred hours. Hours are purchased in blocks, using an online account, and are immediately available for the user to deploy as and when they are needed. Unused hours are credited back to the users account to be used at a later date. A bulk discount is applied to purchases, so the more hours a user buys, the lower the cost per hour. Power-on-Demand license scheme provides users with a flexible simulation environment that expands and contracts based on workload. This could be used either as a “burst capacity,” to allow users with a traditional annual license to top up their simulation capability at times of peak demand (allowing them to reduce the size of their annual licenses to mean demand level), or to provide an on-demand capability for occasional users. Cloud Computing Each license allows you to access unlimited computing resources, either on your own cluster or using those of cloud computing services such as Amazon EC2 and SGI Cyclone (or any other public or private cloud), giving users immediate access to almost unlimited computing resources without having to worry about infrastructure or security issues. The latest versions of STAR-CCM+ are available on both Amazon EC2 and SGI Cyclone, so the user need only download the light-weight STAR-CCM+ client on their local machine (usually a standard laptop), purchase some hours, and begin the simulation. Although we do not anticipate that our users will immediately begin to run all of their simulations on the cloud, in the few weeks after the Power-onDemand scheme was released, CD-adapco was inundated with requests from our existing customers, all of whom were keen to embrace a more flexible approach to engineering simulation. <

i FOR AN ONLINE VERSION OF THIS ARTICLE, VISIT: www.cd-adapco.com/press_room/2010/31-03-cloud.html

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..::FEATURE ARTICLE Automotive

Simultaneous Evaluation on Aerodynamics & Air-Cooling Performances for Motorcycle using CFD Analysis Yoshihiko Sunayama, Ph.D - Group Leader, CAE Group, Digital Engineering Dept. Suzuki Motor Corporation

In the development of a sports motorcycle, a balance must be achieved between low drag to improve performance and good airflow through the cooling system to maintain reasonable fuel economy. Typically, however, a low drag coefficient ( C D ) and increased flow through the heat exchangers are contradictory in nature, as an improvement in one leads to deterioration in the other. With this in mind, Suzuki looked to STAR-CCM+ to help optimize their bike designs by studying aerodynamics and heat exchanger flow simultaneously. In order to develop a set of best practices for future analyses, a study of the influence of turbulence models and mesh density on motorbike performance was performed. STAR-CCM+ was used and, for validation purposes, its results were compared with wind tunnel measurements on a test vehicle. Computational & Experimental Methods Two mesh sizes---coarse and fine---were considered for this study, both consisting predominantly of hexahedral (trimmed) cells and polyhedral cells in the heat exchangers. Both meshes were generated automatically with STAR-CCM+ and volumetric refinements were used to better capture flow structures around the bike in general and through the heat exchangers specifically. The resulting mesh consisted of approximately 17 millions cells for

the coarse grid and around 24 millions cells for the fine one. The k-ε realizable and k-ω SST turbulence models were also studied. A suitably sized computational domain is key to the accurate, and therefore successful, analysis of vehicle external aerodynamics (of any configuration). Consequently, a rectangular box 8 times the width, 5 times the height and 6 times the length of the bike was used as our simulation domain to ensure that the boundaries had no detrimental effect on the flow field near the motorbike. With the external boundaries in place, a blockage ratio of just 1.6% was achieved. In order to assess the accuracy of the computational results, the values of CD and of the flow velocity through the heat exchangers were measured in the wind tunnel with vane-type anemometers attached at 16 different locations on the back face of the radiator. g

❐ FACTS Boasting an all-new compact engine, shorter wheelbase and new styling, the new GSX-R1000 raises the bar once more in the hotly-contested Supersport class. With significant changes in the engine department, the new GSX-R features a more over-square bore and stroke, larger, titanium valves, a higher compression ratio, and 12 hole fuel injectors, to deliver a finer fuel mist for more complete combustion. All this with a power-plant that is 59mm shorter from front to rear. And it’s not just the engine that’s seen the significant changes either, as the all-new chassis makes the GSX-R1000 more agile than ever before. With a unique engine and chassis package, the aggressive aesthetics and rider controls top-off the flagship GSX-R. With the unique Suzuki Advanced Exhaust System, featuring low-slung MotoGP inspired titanium exhausts, a lighter, sculptured fuel tank, on-board lap timer and revised Suzuki Drive Mode Selector controls, the new bike offers the complete sports package.

Suzuki GSX-R1000 2009.

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Inverted telescopic, coil spring, spring preload fully adjustable, rebound and compression damping force fully adjustable Link type, oil damped, coil spring, spring preload fully adjustable, rebound and compression damping force fully adjustable Radial mount, 4-piston calipers, 310 mm disc, twin 1-piston caliper, 220mm disc 120/70 ZR17M/C (58W) tubeless 190/50 ZR17M/C (73W) tubeless

Front suspension: Rear suspension: Front brakes: Rear brakes: Front tyres: Rear tyres:

999cc Four stroke, liquid-cooled, DOHC 74.5 mm x 57.3 mm 12.8 : 1 Wet sump Electronic ignition (Transistorised) Fuel injection Electric 6-speed constant mesh Chain

Engine capacity: Engine: Bore: Compression ratio: Lubrication: Ignition: Fuel system: Starter: Transmission: Drive:

2045mm (80.5in)

710mm (28in)

1130mm (44.5in)

1405mm (55.3in)

810mm (31.9in)

203kg (447.5lbs)

17.5litres (3.8 UK gallons)

Overall length:

Overall width:

Overall height:

Wheelbase:

Seat height:

Kerb Mass:

Fuel capacity:

❐ FACTS

CHASSIS SPECIFICATION

ENGINE SPECIFICATIONS

DIMENSIONS & WEIGHTS

Suzuki GSX-R1000 2009 SPECIFICATIONS

..::FEATURE ARTICLE Automotive

Creativity - a human gift to develop products that promote better living conditions and satisfy people’s need. Since the founding of Suzuki Motor Corporation, we have always pursued providing ‘value-packed products’ as one of our manufacturing philosophies. Realizing that the value differs according to the times, country and lifestyle, we are fully determined to challenge for the creativity to make such products for customers around the world with our advanced technologies and enthusiasm.

i MORE INFORMATION ON SUZUKI GSX-R1000 2009: www.suzuki-gb.co.uk/bike/gsxr1000k9/tech/

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..::FEATURE ARTICLE Automotive

ABOVE Type A: fine mesh

ABOVE Pressure Distribution

ABOVE Type B: coarse mesh

Drag analysis The experimental and computational results of CD were compared. Cases 1 and 2 are the results of the SST k-ω model with the mesh of type A (fine) and B (coarse) respectively, while Cases 3 and 4 are the results of the realizable k-ε model with, again, the mesh of type A and B respectively. Across all mesh/turbulence model comparisons, the maximum difference between the experimental and the computational results was found to be 2.9%. When comparing turbulence models on a same mesh, the values of CD for the SST k-ω were 0.017 to 0.019 higher than those given by the realizable k-ε model. When comparing mesh sizes for a given turbulence model, the values of CD for the finer mesh were found to be 0.010 to 0.012 higher than those obtained with the coarse mesh. In Case 1, the total drag force of the test vehicle was broken down into the contributions of its different part. This showed that the largest contributor

to the overall drag is the cowling, responsible for approximately a quarter of the total drag. The radiator produces the second higher drag component, representing 13.4% of the total. These observations only highlight the importance of optimizing the radiator flow to minimize the drag while maintaining the cooling performance. For this analysis, the accuracy of STAR-CCM+’ predictions turned out to be more than acceptable, making STAR-CCM+ a reference design tool for future bike applications, providing that an adequately fine mesh and the correct turbulence model are used. Radiator flow The experimental and computational results of the radiator mean flow velocity were compared for both mesh sizes and turbulence models. Velocities were found to be overpredicted by 8.1 to 16.8% compared to experimental

(a)

1.42

1.00

1.02

1.11

1.16

0.83

0.98

0.99

0.89

0.99

0.91

0.86

1.24

1.66

1.45

1.29

(b)

1.34

0.96

1.07

1.14

1.34

0.99

0.91

1.19

0.99

1.22

1.27

1.12

1.26

1.43

1.71

1.43

Table 1 Velocity distribution of flow passing through radiator in (a) Case 1 and (b) Case 3, normalized by experimental velocity.

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..::FEATURE ARTICLE Automotive

Suzuki GSX-R1000 2009.

ABOVE Velocity field around the central section of the motorbike

ABOVE Oil cooler

measurements, with the best agreement reached when using the k-ε SST model - although the results quality showed a higher mesh dependency than with the k-ε turbulence model. To study the flow velocity distribution through the radiator, the velocity was calculated at four different locations, C1, C2, C3 and C4. The results, normalized by the experimental velocity, are shown in Table 1. It can be seen that the best agreement with experiment, for both Cases 1 & 3, is reached in the upper central region of the radiator at points C2 & C3, where high velocities are reached as the bulk flow goes straight through the radiator, between the front forks, tire and cowling. This good agreement between computational and experimental results in the higher velocity regions of the radiator is likely due to the “simpler” nature of the flow field there. The flow in the other areas of the radiator is relatively difficult to model and simulate properly as it includes shear flows from the front forks and flows almost parallel to the frontal surface of the radiator. Conclusion In order to assess both the aerodynamics and air-cooling performances of a motorcycle in a single simulation, a set of best practices has had to be developed and validated. The conclusions obtained from this study are as follows: • An excellent match (less than 3% difference) was found between STAR-CCM+’ predictions and wind-tunnel measurements of CD, giving us the confidence to use STAR-CCM+ for drag evaluation of motorcycles. • A good match (less than 10% difference) was found between STAR-CCM+’ predictions and wind-tunnel measurements of the flow mean velocity throughthe radiator. This shows that although STAR-CCM+’ results are accurate enough for the assessment of air-cooling performance of motorcycles, there is still scope for improvement in the accuracy of STAR-CCM+’ predictions. • The results obtained with the SST k-ω turbulence model showed a higher sensitivity to the mesh size; however using this model in combination with a fine grid led to more accurate results than when using the realizable k-ε turbulence model. <

ABOVE Radiator

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

ABOVE Numerical results for the simple prototype

ABOVE Thermography for the simple prototype

ABOVE Example internal flow of a rear lamp

RIGHT Example bulb temperature

AMET is a high-tech engineering company, active in the design and development of mechanic and mechatronic products and processes based on numerical simulation.

Olsa supplies worldwide components for interior and exterior lighting for vehicles. In order to produce the best products, Olsa R&D laboratory uses the most innovative and modern solutions.

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..::FEATURE ARTICLE Automotive

Turning on the light on heat transfer Flavio Cimolin, AMET S.r.l, Andrea Menotti, Olsa S.p,A, Lucia Sclafani, CD-adapco

The design of rear lamps for the automotive industry is becoming more challenging as an ever finer compromise between product lightness and resistance to heat loads needs to be found. Only after engineers have successfully achieved this delicate but essential balance, style and aesthetics considerations can be added to the equation. OLSA, supplier of interior and exterior lighting components for the worldwide automotive industry, and AMET, an engineering company that specializes in the design and development of products and processes using numerical simulation, have developed a complete methodology for the thermo-mechanical simulation of a lamp. This comprehensive model tracks the exchange of convective and radiative thermal energy from the filament of the lamp, and includes transparency effects from the bulb as well as interactions with other components in the assembly. The approach has been successfully validated by experimental comparison with a simple prototype of a lamp, with results from STAR-CCM+ showing good qualitative agreement and perfect energy balances. The challenge When designing an automotive lamp, accurately predicting its thermal behaviour is essential: intense heat loads can cause severe plastic deformations of both the body and the external lens, possibly resulting in global damage to the whole optical component. This is a significant problem when considering today’s stylish designs which demand the use of thinner and lighter materials (often deployed in unconventional geometric configurations).

In order to be approved for use on an automobile, a newly developed rear lamp must pass a series of physical tests designed to represent the most testing thermal conditions that the lamp is expected to face in operation (including combinations of heat, rain, wind or moisture loads). The use of simulation from the earliest stages of the design process can help to significantly decrease the probability of failing these tests, greatly reducing both costs and development time. Setting up the model An automotive lamp can be seen as a complex thermo-mechanical system in which the stresses acting on the components depend strongly on the heat transfers between them. The principle source of thermal energy is the filament, which can easily reach temperatures of 3500°C or more, and emits radiative energy. Part of this radiation is absorbed by the transparent bulb, which reaches a temperature of 400-600°C, and therefore becomes a significant source of radiation in its own right. Using the STAR-CCM+ surface-to-surface radiation model and a Kirchhoff model of transparency, the model reproduces the fundamental mechanisms of radiative heat transfer. Although radiation is the dominant heat transfer mechanism, the influence of natural convection is also significant as the large temperature differences between the bulb and the main body of the lamp drive the recirculation of the air inside the lamp, resulting in “hot-spots” such as the one directly above the bulb. A typical rear lamp model - including solid meshes of multiple bulbs and other optical or screening-related components, as well as the internal air volume - requires a mesh size of at least 500,000 cells. If external air is considered, the number of cells can exceeds 3 million, leading to several hours of multi-processor computation for a steady state simulation. g

❐ FACTS

ABOVE Mesh of the rear lamp

Headlights are one of the most highly regulated systems on any automobile. The first vehicle headlamps were officially introduced during the 1880s and were based on acetylene and oil, similar to the old gaslamps. The first electric headlamp was produced by the Electric Vehicle Company based in Hartford, CT in 1898. Until 1975, all US headlights had to be round, non-halogen, DOT-approved sealed beam units with 2 large dual-beam bulbs or 4 small single-beam bulbs which gave no room for stylish headlights.

i FOR MORE INFORMATION ON OLSA VISIT: www.olsa.it

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..::FEATURE ARTICLE Automotive

ABOVE Geometry of the simple prototype

ABOVE Heat extraction by the oven

Validation and verification The verification and validation of the approach have been assessed by means of both theoretical considerations and experimental investigations. When considering simple geometries, the radiative heat transfer between the filament, the bulb and the body of the lamp can be directly computed by means of Stephan-Boltzmann law together with energy conservation. This approach shows perfect agreement between the numerical and the theoretical results. Even when considering a very complex lamp configuration in external air, the energy balance between the power dissipated from the filament(s) and that exiting the system is well captured by the numerical model. In order to perform a thorough validation of the methodology, a cubic prototype of a lamp was considered and investigated experimentally by means of infrared thermal camera images and thermocouples. The numerical simulations of the cubic box in external air showed fairly good agreement with the experimental measurements, with an overall error less than 5% on the body of the box. These comparisons are necessary in order to correctly calibrate the important physical parameters of the model, such as the emissivity, reflectivity and transmissivity coefficients on different surfaces, or to exactly calculate the heat transfer coefficient of the external boundary of the lamp.

the heat transfer associated with natural convection has a significant influence on the overall thermal field. In addition, unsteady simulations are essential in the case of complex multi-bulb lamps, where the tests are performed by turning on and off different lights at different scheduled times. The application of a standard unsteady simulation would currently require a very large amount of computing resources. However, a smart alternation of the solvers associated to energy and flow (by means of the “Freeze Flow” and “Freeze Energy” options) results in a dramatic CPU time reduction, making this apparently unfeasible simulation possible using available computer resources.

Advanced issues Thorough investigations of the type described above lead to a confident applicability of this numerical methodology to increasingly complex (and increasingly realistic) geometries. However, the secondary but nonetheless important issue of lamp ventilation and natural convection also requires consideration, as highlighted by the so-called “ventilated oven test”. Another important issue to deal with is the case of open lamps, in which

i FOR MORE INFORMATION ON AMET VISIT: www.amet.it

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Conclusions This new STAR-CCM+-based CFD methodology for the thermo-mechanical simulation of optical devices has proved to be robust and capable, and has helped design thermo-mechanical aesthetically pleasing lights with durable, high-quality, all-weather performance. Furthermore, deploying simulation early in the design process has enabled a significant reduction in the amount of physical testing required to bring products to market.<

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

ABOVE Internal temperature

ABOVE Geometry of the automotive rear-light

ABOVE Centerline plane temperature and velocity field inside domain for the simple prototype

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..::FEATURE ARTICLE Automotive

Le Mans Prototype: Increasing Front Downforce Jean-Philippe PĂŠlaprat - ORECA, France

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..::FEATURE ARTICLE Automotive

ABOVE Coefficient of pressure on the bodywork and flaps (side view)

ABOVE Coefficient of pressure on the bodywork and flaps (front view)

The aerodynamic configuration of a Le Mans Prototype depends on the nature of the track where it races: some pre-installed par ts may be adjusted, such as the rear wing main plane or the flap. Regulations permit the homologation of various versions of the aerodynamic package but place restrictions on how many changes can be made. Typically, up to two “flaps” are allowed to be added on the front fenders in order to increase the front downforce. These flaps are the object of the aero analysis and optimization described in the ar ticle.

The ORECA Group has been a leading contender in motor racing for 35 years. Oreca competes in Le Mans Series and 24 hrs of Le Mans with his own prototype, and also in World Touring Car Championship for Seat Motorsport. Two departments are concentrated on business/marketing operations: the sale of equipment and accessories, and the Special Event Department for marketing and incentive operations. www.oreca.fr/UK

RIGHT Iso-surface of Q-Criterion

Oreca and CFD Oreca started to work with CFD software at the beginning of 2009 and, after evaluating different packages, it was found that STAR-CCM+ offered the best compromise in terms of ease of use and accuracy. Our first aim was to get a better understanding of Le Mans Prototype (LMP) aerodynamics as well as a good support for wind tunnel testing. Moreover, CFD enabled us to develop the aero-package throughout the season thereby reducing our dependence on wind tunnel testing. Aero-configurations LMP cars are designed to compete in LMS (Le Mans Series), ALMS (American Le Mans Series), Asian Le Mans Series and, of course, the 24 Hours of Le Mans. The tracks used for these Championships have different characteristics. On the fastest track, the top speed is over 320kph, the average speed is around 230kph and the straights represent 80% of the track. On the slowest track, the top speed is only 290kph, the average speed is around 175kph and the straights represent 60% of the track.

The aerodynamic requirements for these different types of track are obviously very different. Therefore, the ability to analyze different configurations rapidly is needed. The fast tracks necessitate a reduction in drag and an improvement in aerodynamic efficiency, while on slow tracks the focus is on increasing the overall downforce. Apart from optimizing the levels of aerodynamic drag and downforce, some other aspects of race car aerodynamics such as aerodynamic balance or ride height sensitivity need to be studied. Simulation Properties At Oreca, only “full-vehicle” simulations are carried out, as the addition of flaps at the front of the car can significantly alter the air flow under the car and into the rear diffuser. The k-Omega SST turbulence model was used in conjunction with a trimmed hexahedral mesh, and prismatic layers were added on the car’s surface to help resolve the flow inside the boundary layer, thereby increasing the accuracy of the results. The floor was set up as a “moving wall”, with its tangential velocity being equal to the inlet velocity, while boundary conditions at the wheels and brake discs were chosen to account for their rotational velocities. g

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..::FEATURE ARTICLE Automotive

Dive-Plane

Splitter Side-Panel

ABOVE Configuration 2

ABOVE Configuration 1

ABOVE Configuration 2 (top view)

ABOVE Trimmer mesh of the bodywork

Geometry tested On the front of the car, the rules and regulations permit the addition of up to two “flaps”. The “flaps” can be considered as either a dive-plane or a splitter end plate. The Baseline was a standard HDF (High Down-Force) configuration chosen after the wind-tunnel tests results, with double small dive-planes, which is a good configuration in terms of efficiency. The target was to design new parts which would increase the total level of downforce, switch the aero-balance to the front and keep the same level of aerodynamic efficiency. Two other double dive-plane configurations were tested, the first with bigger parts and the second with splitter endplates combined with a dive-plane. Results For both configurations, parameters such as height and angle of attack were varied to find an optimal design. Furthermore, in order to assess the differences between the various new components, visualization of the pressure coefficient (CP), wall-shear stress and Q-criterion were compared. Using a force report, we could check the impact of each part of the dive-plane and splitter side panel. It was easy to see, for example, whether the effect of the side-panel would modify the underbody air flow or act only under the splitter. As a final result of this aerodynamic analysis, we found that the double dive-plane is the best compromise in terms of downforce, balance and aerodynamic efficiency. With a new aerodynamic package developed with STAR-CCM+, Team ORECA Matmut AIM competed at the prestigious 2009 24 Hours of Le Mans race. The aerodynamic advances achieved during this optimization process made strong running possible during one of the most famous races in the world. < RIGHT (courtesy ORECA Racing) Le Mans in its genes! ORECA has been a constructor since the end of 2007, and it has already made a name for itself with the ORECA 01 racing in LM P1, and the Formula Le Mans prototypes. The Signes-based Group has used the experience gained with these two cars to build the ORECA 03. This new prototype will be on sale for teams wanting to race in 2011 in the Le Mans 24 Hours and in the different Le Mans Series in the LM P2 category.

i FOR MORE INFORMATION ON ORECA VISIT: www.oreca.fr

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CAR

Base

Dive-Plane + Endplate

Dble

SCX

5,28%

9.50%

SCZ

4.27%

8.03%

FRONT BALANCE

3.75%

4.15%

ABOVE Close-up of the dive plane

..::FEATURE ARTICLE Battery

LEFT Streamlines of cooling air flow around discharging battery cells MIDDLE Maximum predicted battery cell temperatures for different discharge rates RIGHT Screen shot of a 30KWh battery pack colored by battery cell temperature

STAR-CCM+ Battery Simulation Module

Since our collaboration was announced last year, the development teams of both CD-adapco and Battery Design LLC have been working hard to bring this exciting project to fruition. The principal objective of the project is to deliver a tool that will allow engineers to simulate flow, thermal and electrochemistry within a single code. Achieving this goal required our multidisciplinary team to overcome numerous hurdles; as well as the fundamental solver enhancements required to provide the pioneering simulation, the upstream pre-processing of battery geometry and input data was also a major task. This article expands on some of the details of the technology and looks at the use of software from the point of view of a battery engineer. Setting up the Analysis “Where do I start?” is a common question we encounter when discussing the input requirements for battery simulation. Of course, an understanding of the electrical and thermal performance of a battery under relevant test conditions is required to ‘characterize’ the battery and hence its response to the simulated conditions predicted. This upstream work is completed using the ‘Battery Design Studio’ package, which builds a characterization from battery discharge curves and other associated data. Geometry information of the battery and surrounding components is also required, the former being automatically generated by STAR-CCM+, with the latter imported from CAD packages or created using STAR-CCM+ 3D-CAD. As battery modules and packs tend to be constructed from a series of identical cells and conducting or structural components, STAR-CCM+’s Battery Simulation Module provides tools to copy out an assembly to quickly create a module or pack. This expedites the creation of the simulation model and allows battery engineers to create fictional packs, as well as respecting physical designs, exploring ‘what if’ cooling scenarios and design changes. The Solver Strategy As already discussed, the pioneering solver computes flow, thermal and electrochemistry quantities within a single solution. The solver can handle all forms of battery cooling from free convection, through forced air convection up to liquid or refrigerant cooling. The interface allows users to choose the battery model solver, ranging from equivalent circuit models - whereby the response of the battery to an electrical load is modeled using a simplified circuit model - to a more complex electrochemistry model - providing detailed

information about the internal cell quantities. These battery models are dependent on the surrounding thermal conditions which will influence their electrical performance during the analysis. By solving both thermal and electrochemistry quantities within one solution, a design engineer can instantly see the impact of a specific installation upon a given cell’s performance. This allows installation designs to be compared, for example to judge the maximum non-uniformity of temperature across a module of battery cells, facilitating design decisions. Since the same core battery cell behavior is maintained, different simulations can easily be compared. The Battery Simulation Module provides simulation data for the battery cell that shows the internal gradients created by the location of current carrying tabs and the applied cooling strategy. Within large format lithium ion batteries, those used in traction applications, controlling these internal gradients, whether thermal or electrical, is the key to obtaining long life from a particular battery pack. Visualizing these gradients as part of a larger simulation provides invaluable data to battery engineers. Post Processing Having computed what potentially could be a large transient simulation, the engineer can now extract data concerning the thermal and electrical performance of this simulated battery pack. The graph above shows output from monitoring the temperature of a battery cell during a range of discharge conditions. Understanding the temperature at which a cooling system’s performance matches a cell’s heat generation is crucial to controlling cell temperature. This is a typical scenario and the Battery Simulation Module allows an engineer to achieve the optimum engineering solution from a given set of spatial and performance constraints. The Battery Simulation Module is available in STAR-CCM+ 6.02 as an additional add-on.

i FOR MORE INFORMATION: steve.hartridge@uk.cd-adapco.com

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..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Aerospace BELOW Vertical component of the velocity field around UAV1 and UAV2 shown in a xy-plane located right above the wing upper surface

UAVs in Close Formation Flight Deborah Saban, Technical Marketing Engineer, CD-adapco.

ABOVE Spanwise component of the velocity field around UAV1 and UAV2 shown in a xy-plane located right above the wing upper surface

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..::FEATURE ARTICLE Aerospace

ABOVE Tangential velocity field behind UAV2

The last decade has seen an increased interest in the development of Unmanned Aerial Vehicles (UAVs) and their applications which are no longer restricted to the military field of operations. UAVs - either remotely piloted or fully autonomous - provide a safer, cheaper alternative to larger, piloted aircraft, as well as a valuable ‘bird’s eye’ observation platform mid-way between ground-based sensors and high-flying satellites. These considerations have opened the way to UAV applications in many other fields, such as homeland security (police surveillance, border patrol, etc.), public services (fire fighting, search and rescue, power-line and pipeline inspections, chemical and pollution sensing, climate monitoring, etc.), and the commercial sector (geographic surveys, aerial communications networks, crop spraying, etc.), and made them the choice of predilection to perform the ‘3D’ (Dirty, Dull and Dangerous) missions. However, as some missions – such as air-to-air refueling, weapons reloading, aerial launch & recovery or aerial surveillance – require multiple vehicle close formation deployments, a detailed understanding of the wake vortex effects caused by one vehicle upon another is needed. This article aims at demonstrating how the CFD software, STAR-CCM+, can be used to investigate the nature of dynamic air vehicle interactive coupling and its consequences during close formation flights. A formation of two identical tailless pushers, UAV1 and UAV2, is considered for these purposes. Both vehicles are flying at the same level in a station keeping scenario and the follower is located 0.9 wingspan behind and 0.9 wingspan starboard of the leader.

The entire simulation process, from pre-processing to post-processing, is performed using CD-adapco’s flagship software, STAR-CCM+. STAR-CCM+’s high level of automation enables the user to focus on engineering data analysis rather than on time-consuming repetitive tasks, as demonstrated through the following steps: 1. The airframe geometry of one Pusher UAV, UAV1, is imported and automatically cleaned up and prepared for meshing: STAR-CCM+’s surface wrapping feature enables any imported geometry, regardless of its complexity and initial quality, to be covered by a clean ‘second skin’ surface mesh. This optional operation can be performed within a few minutes using STAR-CCM+, thereby sparing the CAD and CFD engineer of long and dull hours (if not days) of surface repairing where each individual cell needs to be addressed independently. 2. UAV2 is generated by simply copying and pasting UAV1 to the desired location. This operation can be repeated each time a UAV needs to be added to the formation. g

ABOVE Vorticity magnitude behind UAV1

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..::FEATURE ARTICLE Aerospace

RIGHT Geese flying ‘V Formation’

3. A large boundary volume enclosing UAV1 and UAV2 is then chosen and meshed, using either tetrahedral, polyhedral, or trimmed (hexahedral) cells. The use of polyhedral meshing, which is another of STAR-CCM+’s innovative features, can provide the same accuracy as a typical tetrahedral mesh with at least 5 times fewer cells. Once again, STAR-CCM+ enhances productivity and efficiency without compromising the accuracy of the solution.

4. Several levels of mesh refinement are set up through the use of volumetric controls in order to fully capture UAV1’s wake and its effects on UAV2.

5. The properties of the physics continuum are then defined, including the model to be used, its reference values and initial conditions. STAR-CCM+ is now ready to perform the computation, at the end of which the solution can easily be analysed using STAR-CCM+’s colorful and powerful post-processing tools. The post-processing results clearly show how the upwash, downwash and sidewash generated outboard and inboard of UAV1’s wing tips can affect UAV2’s stability. They confirm the well-known fact that wake vortices represent severe atmospheric disturbances which can be, depending on the relative positions of the air vehicles in the formation, either beneficial or detrimental, not to mention dangerous. Dangerous because of the strong and sometimes unexpected rolling moment that can be induced on a wake-encountering vehicle by such a concentrated core of vorticity. Beneficial because if the follower positions itself in the up-current generated by the leader, the induced drag of the trailing aircraft is dramatically reduced, leading to significant fuel savings and/or an increased range with a given payload. This translates into real economic and environmental benefits, which are certainly not to be overlooked in a time when the emphasis is set on developing newer, greener and cheaper technologies.

This trick has not been invented by CFD engineers: geese and ducks have been using it in their migration V-formation shapes since the beginning of time. However, STAR-CCM+’s colorful post-processing tools enable the CFD engineer to demonstrate it in a more artistic way than ever before. Not just Art for Art’s sake though. STAR-CCM+, with its fast, powerful and user-friendly all-in-one integrated environment, proves to be the ideal platform to assess the benefits, as well as the risks and issues, associated with wake vortex evolution and encounter, thereby providing the enabling science on which the development of new procedures and protocols for UAV close formation deployments may be securely based. <

RIGHT Tangential velocity field behind UAV2

STAR-CCM+ Product Features Single Integrated Process STAR-CCM+’s unique simulation process delivers unrivaled ease-of-use and automation to accurate, engineering CFD. CAD Embedding Powerful CFD from within your chosen CAD package: SolidWorks, Pro/E, CATIA V5 or Unigraphics NX. Surface Wrapping Spending hours or days cleaning CAD or preparing a surface mesh? The Surface Wrapper will cut this time to minutes.

Automatic Meshing Technology Advanced automatic polyhedral or hexahedral meshing gives the ultimate combination of speed, control and accuracy. Additional Physics Modeling The fastest developing solution in CFD, STAR-CCM+ is equipped with a comprehensive selection of physics models. Accurate solutions in an easy-to-use environment.

i VISIT OUR NEW AEROSPACE HUB: www.cd-adapco.com/applications/aerospace

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Turbulence With its extensive selection of turbulence models, STAR-CCM+ is guaranteed to meet your requirements. Post-processing From contours plots, to XY-graphs and streamlines to animations. Extract Engineering insight with STAR-CCM+. Software and Hardware Technology Client-server architecture, object-oriented programming and unrivaled parallel performance, STAR-CCM+ uniquely utilises the latest technology.

..::FEATURE ARTICLE Aerospace

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Bicycle Wheel Aerodynamics:

..::FEATURE ARTICLE Sport

Increasing Workflow Productivity with STAR-CCM+ & FieldView By Matthew N. Godo, Ph.D., FieldView product manager, Intelligent Light

In the world of CFD simulation, maximizing return on investment comes not just from reducing the cost of analysis while increasing output, but from fully mining that output for critical insight and accurate answers. STAR-CCM+ and STAR-CD users are well aware of the many benefits these power ful and popular solver codes bring to the design and engineering process, including the ability to solve complex, large data problems. If analyzing that data can’t be done efficiently and effectively, however, the investment in those resources won’t be fully realized. A high productivity CFD workflow is imperative, both economically and competitively, for exploring multiple designs and complex phenomena within tight design cycles. As we found in a recent study at Intelligent Light, post-processing results with FieldView™ harnesses the value of STAR-CCM+ and STAR-CD solution data and speeds the search for answers, demonstrating both the need for and the value of robust, automated post-processing. Bicycle Wheel Aerodynamics Studying the aerodynamic flow around a rotating bicycle wheel in contact with the ground, including the front fork and frame components, presents a unique CFD challenge. Wind tunnel testing has been used extensively for two decades to study and reduce drag in cycling applications, resulting in significant improvements in equipment and an enhanced awareness of aerodynamics. But

physical wind tunnel testing has significant limitations. Making direct comparisons between test results from different facilities is problematic; contributions to drag cannot be separated out by individual component; vertical forces acting toward or away from the floor cannot be calculated because the wheel is usually affixed to forks; and not least, wind tunnel testing is expensive and time intensive. With today’s sophisticated CFD software and high performance computing resources, we saw an opportunity to put CFD simulation to the test by developing a comprehensive, flexible methodology to model and analyze bicycle wheels. Using STAR-CCM+ and FieldView, we studied multiple wheels and fork/frame combinations at two speeds and 10 different yaw angles totaling 120 cases. The surface wrapping capability of STAR-CCM+ was tremendously helpful in setting up the problems and generating the meshes of each wheel design, handling the detailed geometry well. g

i FOR MORE INFORMATION ABOUT THIS STORY PLEASE VISIT: www.ilight.com/wheel

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..::FEATURE ARTICLE Sport

Technology, Teamwork, Trust For over 25 years, Intelligent Light has been helping customers find the answers to their most challenging problems. Intelligent Light delivers the world’s most advanced technologies for understanding and visualizing large complex data. The FieldView family of products delivers a comprehensive CFD post-processing suite that supports people in mission critical CFD environments. Our long partnership with CD-adapco was born from our shared commitment to meeting the demanding needs of these customers. Industry leaders rely daily on Intelligent Light’s staff for products, consulting, research, and support to make their CFD jobs accurate, fast and easy. Visit us at: www.ilight.com to learn more and experience FieldView for free. www.ilight.com

RIGHT Massless particles called ‘streamlines’ were released from a set of fixed circumferential positions, resulting in highly detailed animations of the air flow. On the suction side we can see that at low yaw, strong recirculation is observed at the top, outer edge of wheel, with weaker recirculation seen at the bottom half, inner edge of wheel. As yaw angle increases, top recirculation extends along front of wheel and combines with inner wheel recirculation. The streamlines and images were created automatically using FieldView FVX routines.

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..::FEATURE ARTICLE Sport

ABOVE Zipp 404 (left); Zipp 1080 (right) In this image, as the flow is drawn into a slotted fork, it can be seen pulling away from the wheel rim and tire. At higher yaw angles, the flow gets trapped behind the fork, and strong recirculation pulls the flow upward.

STAR-CCM+ showed excellent parallel scaling on the complex geometry, making computing this many cases feasible. The tight interface between the two products provided a seamless transfer of FV-UNS files, and by leveraging FieldView’s automation and visualization capabilities, just a few hours of upfront system design resulted in a highly productive workflow that was repeatedly put to the test as the study progressed and new data was added. Meeting research and publication deadlines would have been impossible without the combined strengths of STAR-CCM+ and FieldView. The study’s findings - that drag force does depend on the wheel and is influenced by the choice of the front fork, and that the wheel rim and tire, not the hub and spokes, dominate the overall drag-challenges conventional wisdom and opens up new avenues of exploration for bicycle wheel manufacturers and the cycling industry in general. Robust, reliable automation speeds the workflow During the steady simulations, approximately 3.6 gigabytes of data were generated, while the unsteady simulations resulted in nearly 1.2 terabytes of data. In the past, this quantity of data, its complexity, and the repetitive nature of the calculations would have posed a seemingly insurmountable challenge for researchers. FieldView is particularly well suited to handling transient cases, and we used FieldView’s FVX™ programming language to automate many post-processing tasks, including: • resolving the forces on the wheel into their drag, side, and vertical components; • breaking the resolved forces down to those acting on each component: wheel rim and tire, hub, spokes, and fork; • calculating the resolved forces along the wheel circumference; • creating custom visualizations of flow structures for standardized quantitative and qualitative evaluation. For ease of use, we specifically developed automation routines that were geometry-independent and applicable to both steady or transient simulations with few or no changes. An automated workflow must be robust and reliable, inherently stable and yet flexible in order to evolve and capture best practices.

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ABOVE The surface wrapping capability of STAR-CCM+ delivered high-quality meshes on detailed geometry and allowed the control to maintain surface density on different components.

ZIPP 404

..::FEATURE ARTICLE Sport

DIRECTION OF FLOW t

ZIPP 1080

LEFT Resolved forces around the wheel perimeter were averaged on small circular arc segments for each yaw angle and plotted as a function of the wheel circumference. The tools in FieldView enabled this unique representation of data.

NO FORK

REYNOLDS CARBON

Because FieldView is always 100% backward compatible, these routines can be used without modification with future releases of FieldView. In each instance, tasks that would have taken many weeks to accomplish in a traditional, serial workflow were completed in days. After the initial time invested in writing the routines, we used them extensively - for example, the same FieldView FVX routine was run 60 times to calculate the drag force for all wheel and fork combinations at two speeds. Some tasks, such as calculating circumferential variation, which entailed 3600 calculations for each wheel and fork combination, would simply not have been possible without automation. Advanced, customizable visualization provides insight The larger and more complex a dataset, the more critical it is to be able to quickly and accurately analyze and understand the results. The advanced visualization capabilities of FieldView were put to maximum use in the bicycle wheel study, resulting in unique, unprecedented views of flow features, circumferential variations, and helicity. Two surprises - an unexpected vertical force transition and previously unseen, highly resolved flow structures - were brought to virtual life by the tools and capabilities of FieldView. A method available within FieldView called ‘streamlines’ was used to release massless particles from a set of fixed circumferential positions (created by a simple FieldView FVX routine), resulting in highly detailed animations depicting the flow across the wheel and fork. Much more than just ‘pretty pictures’, these illustrations and animations provided rare insight into the wheel’s aerodynamic performance. The research team was able, in essence, to ‘sit’ on the edge of the wheel and ride through its rotations, capturing and visualizing, for the first time, the complex interactions happening unseen with every turn of the wheel.

BLACKWELL BANDIT

Parallel, batch options fully utilize STAR-CCM+ and HPC investment FieldView maximizes existing hardware and solver/software resources in both concurrent and scalable operations. Intelligent Light’s exclusive batch-only licensing option can cut costs by up to 90% versus individual interactive licenses, while parallel processing can be used to reduce post-processing time on single simulations. Post-processing the large volume of data in the bicycle wheel study was significantly accelerated by STAR-CCM+’s high quality multi-grid export to FieldView Parallel from the transient datasets. Running FieldView Parallel on eight processors accelerated the work by a factor of five. FieldView FVX routines allowed the automated workflow and custom visualizations to be produced in batch mode without user intervention. Batch-only licensing also meant we could post-process, assemble, and interpret multiple cases and time steps concurrently, while keeping the STAR-CCM+ solver running at the same time to generate additional solution data. Performing post-processing while solutions were being generated, and without having to move data off the server due to FieldView’s client-server operation, greatly increased the research team’s work capacity and saved significant time. High productivity CFD wins the race For bicycle wheel manufacturers and designers, the findings of this study offer new and intriguing avenues of exploration in the quest for competitive advantage. Good agreement with experimental wind tunnel studies suggests that the methodology we developed holds considerable promises for future research. Overall, the study provides compelling evidence that CFD simulation can indeed be used to tackle problems and questions previously considered too complex to be easily solved. The power of the STAR-CCM+ solver and the automation and visualization capabilities of FieldView combined to create a highly productive, fast and efficient workflow that maximizes every resource - software, hardware, people, and time - and sets the stage for future discoveries. <

i FOR MORE INFORMATION ABOUT USING FIELDVIEW WITH STAR SOLVERS, PLEASE VISIT: www.ilight.com/cd-adapco

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..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Building Services

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.

RIGHT Streamlines with Personal Breeze turned on

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..::FEATURE ARTICLE Building Services

Feel an Open Window Anywhere

Personal Breeze Air Purifier

Joseph Kummer and JB Allred, Propulsive Wing LLC

Airborne allergens and contaminants found in public places have been proven to have an adverse effect on people, such as a reduced productivity at the workplace, an increased exposure to diseases on airplanes, unhealthy learning environments for children, and sometimes the occurrence of secondary infections in hospitals. One potential solution is the use of personal air ventilation systems, or PAVs. As the problem of poor indoor air quality reaches near epidemic levels (to the extent that certain environments are said to suffer from “Sick Building Syndrome”) and with people spending the vast majority of their time indoor, a solution needs to be found to help the millions of people who suffer due to transmitted disease and allergic reactions to airborne pollutants. Large, bulky, floor air purifiers are generally effective in small to medium rooms but tend to be noisy, expensive, and to consume large amounts of energy. Furthermore, in an open office setting, due to the large room volume and high airflow mixing, these units have only a minor impact on overall air quality. At the other end of the spectrum, small wearable air purifiers typically do not remove contaminants well, and many release ozone as a bi-product of the filtration process, which is itself a pollutant. With funding from the Syracuse Center of Excellence and U.S. Environmental Protection Agency, Propulsive Wing LLC, in collaboration with Allred & Associates Inc. and Syracuse University, has developed the Personal Breeze Air Purifier System, a revolutionary personal air purifier that reduces contaminant and allergen exposure, delivering clean, fresh air to an individual. This methodology, which utilizes the individual’s self generated thermal plume to enhance cleaning effectiveness, is compact, quiet, and consumes only 2 watts. By attaching the Personal Breeze to the front of a desk or to the tray table on an airplane, the user enjoys a light, refreshing breeze of filtered air. Instead of allowing allergens to flow freely up to the breathing zone, the contaminated airstream is diverted, filtered, and then re-injected back into the natural thermal plume. This type of personal air purification provides filtered air to the user for only a fraction of the power consumption and noise of other products. In “breeze” mode, the air purifier simulates the natural fluctuations of real wind: it feels like there is an open window near you, wherever you happen to be. The engineering simulation tool STAR-CCM+ was used to design and develop the Personal Breeze Air Purifier. Simulations were performed of a person working at a desk, onto which the PAV device has been attached. The PAV draws in air from the occupant’s thermal plume, filters it, and blows out a stream of clean air under the person’s chin. Both the external (around the person) and internal (inside the ducting) airflows were modeled and simulated, and the results were used to optimize the air purifier configuration. A number of cases were simulated with the Personal Breeze both off and on. In order to reduce the grid count, simplify the calculations and enable parametric studies, the rotating cross-flow fan of the Personal Breeze was modeled using a simple velocity inlet; this enabled the simulations to be run in steady state g

..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Building Services

Testing of Personal Breeze in Indoor Air Quality Chamber at Syracuse University using Thermal Manikin

Personal Breeze attached to desk and plugged into laptop computer via USB port

Velocity magnitude contours with Personal Breeze fan on

Velocity magnitude contours with Personal Breeze fan off

mode, thereby significantly reducing the simulation time. The grid was refined near the person, the laptop computer, and in proximity of the air purifier in order to correctly resolve the behaviors of the exhaust jet and of the flow in the thermal plume. When the purifier is turned off, the thermal plumes rising from the person and the computer are clearly visible: STAR-CCM+ results show that the air breathed by the person originates from the floor, and moves up through the region at the front of the desk - where the PAV is optimally located - before reaching the breathing zone. When the Personal Breeze is turned on, most of the air which reaches the breathing zone is filtered. Parametric studies were performed to evaluate the effect of the outlet flow velocity and angle in order to optimize the effectiveness of the device and minimize its power consumption. One important characteristic of the Personal Breeze system is that the direction of the natural air flow is only very slightly altered; therefore, the energy input needed by the PAV is considerably reduced compared with a system which aims at significantly changing the flow patterns. Internal aerodynamic studies regarding the flow path within the air purifier were also performed. In particular, the relationships between fan size and speed, filter type, and filter and duct geometries

were investigated to optimize both the power requirements and the dimensions of the PAV. In addition to being an effective filtration solution, the Personal Breeze was designed to be convenient to use in an office setting: the unit interfaces with a computer for power, control, and performance monitoring. Finally, in order to assess and validate the effectiveness of the Personal Breeze system, prototypes were tested in the Building Energy and Environmental Systems Laboratory at Syracuse University. Compared with the ambient air, a reduction of up to 60% in particle contaminant levels in the breathing zone was demonstrated. The final design was proved to meet all specifications, including power consumption smaller than 2.5 watts, Windows-based control, rechargeable battery for portability, on-board environmental sensors and easy filter replacement. Without STAR-CCM+, this would not have been possible within the time-frame of the 1-year grant period. Follow-on designs currently in development will add heating and cooling, humidification and dehumidification, and several other features, with the objective to provide a complete personal environmental solution for the office worker and the traveler. <

i FOR MORE INFORMATION ON PROPULSIVE WING PLEASE VISIT: www.propulsivewing.com

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..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Building Services BELOW Meshed model of a man working at a desk with a laptop computer and a Personal Breeze Air Purifier

BELOW RIGHT Streamlines with Personal Breeze turned off

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..::FEATURE ARTICLE Flow Control

Mark Eight Control Valve Features:

• Straight-through flow allows higher Cv per given size over globe style valves • Less restriction through seat permits less line turbulence • Interchangeable part with other Mark series valves for less inventory • Accurate, high thrust cylinder actuator to shut off against high pressure drops

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..::FEATURE ARTICLE Flow Control

FLOWSERVE

STAR-CCM+ Enables the Optimization of Flow Coefficients for Large Control Valves Gifford Z. Decker, FLOWSERVE - Flow Control Division.

Flowserve is the recognized world leader in supplying pumps, valves, seals, automation and services to the power, oil, gas, chemical, and other industries. With more than 14,000 employees in more than 56 countries, we combine our global reach with a local presence.

ABOVE CAD geometry rendering

The increasing demand for accurate values of the flow capacity coefficient (Cv) for large and non-standard control valves (i.e. those with a diameter of 12 inches or more) has made Computational Fluid Dynamics an extremely valuable tool to reduce the potential high costs and development time associated with flow-testing. For Flowserve, Flow Control Division (FCD), CD-adapco’s flagship engineering simulation software STAR-CCM+ has provided that capability. Efficiency and lead time in the population of Cv values for non-standard and large size control valves can be improved by eliminating flow testing and using CFD to generate accurate values of the Cv. Through the positive outcome of a series of tests, Flowserve FCD has successfully demonstrated how STAR-CCM+ can be trusted to provide customers with highly reliable Cv values for the design and optimization of large control valves. The Challenge This article describes the set-up, results and conclusions of the analysis of a 20-inch Y-body valve whose required Cv value exceeds previous conservative estimates of flow capacity. Instead of conducting iterative experimental tests until a satisfactory design solution is achieved (which would have been very expensive and time consuming), STAR-CCM+ was used to optimize the valve trim parts and obtain the desired Cv value. A validation test was eventually run to ensure that the optimized valve actually meets the Cv requirement. Setup The valve models were created using SolidWorks and imported in STAR-CCM+. The flow being internal and symmetric, only half the fluid domain needed to

RIGHT Streamlines through valve

be modeled. The models were meshed using polyhedral cells and the mesh was locally refined near the throat of the valve in order to capture the high velocity gradients. The fluid physics were then defined using a steady state turbulent flow model, and standard pressure and temperature were used to simulate the conditions prescribed by the testing standard ISA-75.02.01 “Control Valve Capacity Test Procedures”. The boundary conditions were set as stagnation pressure inlet, pressure outlet, and symmetry on the symmetry face. The Cv was computed using a user-defined field function, and for each case, the simulation was run until Cv’s convergence was reached. By keeping the same parameters from one simulation to another and simply using the “replace surface” function to automatically import and test successive valve geometries, the time needed to reach convergence was significantly reduced. g

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..::FEATURE ARTICLE Marine

BELOW Geometry with applied mesh

Results STAR-CCM+ was used to adapt the design of a large and non-standard Y-body valve so that it would meet the specified Cv’s requirement. The fluid flow was simulated with STAR-CCM+ for successive geometries of the valve until the predicted flow capacity coefficient would be high enough. The corresponding geometry was built and sent to a large flow capacity testing laboratory where the valve was tested. The results showed that STAR-CCM+ predictions of Cv matched the experimental measurements within 1%. Further helpful information was collected from STAR-CCM+’s final model, such as: • the pressure distribution in the trim exit holes, • the distance from the trim exit holes to the point of pressure recovery, and • the flow field though the valve. This information can be used to continuously improve the design and functionality of Flowserve’s valves and ensure that they are the most reliable and suitable for customer’s applications. Conclusion CD-adapco’s simulation tool STAR-CCM+ was used to optimize the design of the internal trim of a 20-inch Y-body valve in order to increase its flow capacity to a specified value. Using STAR-CCM+ rather than experimental flow-testing led to a significant reduction in the cost and amount of time required from the design stage to manufacturing and final testing, thereby enabling on-time delivery. The close match between flow-test measurements of the flow capacity coefficient and STAR-CCM+’s predictions increased the level of confidence in STAR-CCM+, making it the reference tool for future similar valve applications.<

ABOVE Pressure distribution in trim exit holes

❐ RECORDS WORLD’S BIGGEST VALVE The biggest valve in operation was constructed by the Lined Valve Co. in 2009 in the United States measures an incredible 34 feet tall, 11 feet wide and weighs 52,000 pounds. It was constructed from wood and fitted to a 96-inch storm and waste water drainage system in Chicago.

ABOVE Flow field visualization

Flowserve VALVES The Flowserve Mark Eight control valve is designed with a unique Y style globe body that provides higher flow capacities and less process turbulence than conventional globe valves. Because of its nearly straight through flow passage, the Y style body is less flow restrictive than a normal globe-style body. This permits less pressure to be converted into velocity as the fluid passes through the seat, resulting in a lower valve recovery factor and higher capacity. Mark Eights straight-through design generates less valve and piping turbulence which significantly reduces harmful noise and vibration levels. Like Flowserves Mark One globe valve, the Mark Eight features streamlined, constant area flow passages, top-entry trim, a four-way positioner, and a high thrust cylinder actuator. The Mark Eight is completely interchangeable with the Mark One except for the body, seat retainer, bonnet, and plug. The packing box, actuator, seat ring, flanges, and gaskets are all standard, off-the-shelf items for fast delivery and minimal parts inventory.

i FOR MORE INFORMATION ON FLOWSERVE PLEASE VISIT: www.flowserve.com

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..::FEATURE ARTICLE Renewable

ENERGY GIANT

ABOVE Windgiant WG 600 wind turbines in action with a height of 42 or 56 metres and a turbine diameter of 22 metres

CD-adapco helps Windgiant to bring Revolutionary Wind Turbine Design to Market Stephen Ferguson, CD-adapco.

In order to meet the world’s energy demands in a sustainable manner, engineers need to deliver robust innovative technology. For 30 years, CD-adapco has enabled energy engineers to do just that in the ‘traditional’ energy sectors, and is now routinely applying the same advanced engineering simulation technology to the renewable energy sector. The Windgiant turbine is based on a revolutionary technology, in which wind flow is accelerated through a multi-bladed fan using a number of concentric aerodynamic shrouds. Compared with traditional three bladed turbine designs, the compact Windgiant turbine delivers a much higher energy per unit surface area and operates at much lower wind speeds (delivering energy at wind speeds as small as 1.5 m/s). Combined with its ultra-low noise energy production (less than 40 dB (A) at 12 meters), the compact design of the Windgiant turbine means that it is suitable for installation in urban residential settings, as well as industrial environments. Currently available in 10kW and 20kW, Windgiant is developing a much larger hybrid-tower which delivers 2.5MW from a combination of wind and solar power. “CD-adapco’s Engineering Services team helped us to demonstrate that our concept was valid, and allowed us to fine-tune our design before investing in expensive physical

prototypes,” said Gerhard Wieser, the designer and innovator behind the Windgiant project. “Having successfully installed a number of Windgiant turbines, I am delighted to report that the devices’ behavior is as predicted by the simulations, with each device delivering plentiful supplies of low-cost electricity in complex urban environments.” Dennis Nagy, CD-adapco’s Vice President of Business Development and Director, Energy Industries, concluded: “In order to maximize their efficiency, most current wind turbines were designed using extensive experimental model testing. Although experimental analysis provides considerable insight into the performance of a particular design, physical prototypes are expensive and time consuming to construct. Engineering Simulation allows the designers of innovative concepts such as the Windgiant turbine to demonstrate their feasibility without committing unnecessary expenditure to the construction of prototypes.” <

Wingiant are widely considered to be ‘the next generation of wind turbine design and construction’. They are a German based organization providing specialized design and construction of small 10kW turbines to super sized 600kW giant wind turbines, as well as the design and construction of wind parks with 6 or more giant wind turbines.

i FOR MORE INFORMATION ON WINDGIANT PLEASE VISIT: www.windgiant.com

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..::FEATURE ARTICLE Renewable

RIGHT Aerial view of a PV panel installation on a factory deck

Prosolia was founded in 2003 in Ontinyent (Valencia,Spain) with the aim of developing environment-friendly energy systems based on solar energy and non-polluting natural resources. With a staff comprising of more than 80 highly-qualified and experienced professionals in the solar energy field, we offer an integral turnkey service to our custumers. Our commitment to the environment and society is evidenced by our sustainable and cost effective systems, as well as our participation in research firms, our sports and cultural sponsorship and our partnership with NGOs.

A Solar Powered Future Qualitative Leap in Renewable Energy with STAR-CCM+ Juan Antonio Carrio - Prosolia.

In 2008, Prosolia Solar Energy responded to the maturity of the Renewable Energy sector in Spain by under taking the development of photovoltaic (PV) panels with increased efficiency. STAR-CCM+, CD-adapco’s flagship software, was chosen to assist us in this challenging task. Introducing STAR-CCM+ to our company allowed our Engineering and R&D&I depar tments to unfold a range of new capabilities by translating the engineering simulation exper tise acquired by CD-adapco throughout the years to Prosolia’s world of renewable and clean energy. i FOR MORE INFORMATION ON PROSOLIA PLEASE VISIT: www.prosolia.com

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..::FEATURE ARTICLE Renewable

ABOVE View of the space between the panel and the roof (10 cm) with prism layers to solve the turbulent flow

ABOVE Flow field and thermal variation on the panels

Renewable energy and CFD Incorporation CFD into our engineering department was not an easy decision for our company. To be worthwhile, the cost of implementing CFD had to be compensated by: • a reduction in assembly costs, • an increase of the level of engineering expertise offered to our customers, and • an improved ability to generate alternative designs. The initial step in the implementation of STAR-CCM+ was to validate its numerical predictions against experimental data using simple models. The satisfactory output of the validation process enabled a ‘best practice’ protocol to be generated for more complex applications. Principle The fundamental premise on which Prosolia relies for PV panel design can be summarized as follows: “A photovoltaic panel is an element that, if correctly installed, does not interfere with its environment and, in turn, generates the maximum possible energy from solar radiation”. This requires the knowledge of structural loads, primarily the effect of the wind on the panels. Different panel configurations were simulated in STAR-CCM+ to determine the most thermally efficient design. The best configuration, based on “the inclination producing the most energy at affordable loads”, was then built and tested. Design and simulation The use of CFD as a tool to design a photovoltaic system is something new. Both global and local thermal effects on the panels are important to ensure that the air flows smoothly through the entire system. First, the original CAD model was simplified and imported into STAR-CCM+ (the effect of these simplifications on the solution was verified to be insignificant a posteriori). Various panel configurations were then added to the factory deck. In order to reach the best compromise between accuracy of the results and computational costs, the computational domain was reduced to a 2D environment and the mesh was locally refined near the panels using volume controls. STAR-CCM+’s automated meshing feature was then used to create a trimmed cell mesh. Secondly, the effects of the wind were assessed. To get the most appropriate panel setting for the given load profile, these were simulated in an empty deck scenario as well as for different panel configurations. As the cell temperature

determines the power output of the panel, the thermal behavior of the PV panels was also examined. A simulation of the flow field around, and thermal variations on the panels enabled the immediate improvement of the configuration’s design, so that maximum cooling could be achieved from the airflow under the panels. Solar radiation was then added to the model. Determining the effects of solar radiation on the panels is a competitive advantage in the renewable energy sector, so using STAR-CCM+ turned out to be a valuable asset for us. The absorption of incident solar radiation by the panels could be accurately calculated, leading to major improvements in temperature control by convection and radiation. To obtain the structural load and thermal parameters of each panel, the free stream velocity was set to 30 m/s and the solar radiation to about 1000 W/m2. All this information is essential to improve a given design, to create new support systems for PV plates with plastic components and to adequately adapt load levels to conventional structures. By helping us to better understand heat transfer phenomena, STAR-CCM+ has enabled us to develop solar thermal systems with improved photovoltaic efficiency, and has become an essential tool for Prosolia’s R&D&I department. Results STAR-CCM+’s predictions of pressure and suction areas for different configurations were compared and the design of the deck was optimized accordingly. To increase the energy production, the photovoltaic panels were tilted by an angle based on the simulations’ results. The turbulent flow was properly resolved and the changes in structural loads well predicted, with numerical results in good agreement with ‘real-life’ temperatures monitored on a PV installation. Conclusions Knowing the flow field around the panels can help the engineer to optimally design the installation. STAR-CCM+’s thermal simulations’ results showed that the cell temperature reduction is directly proportional to the volume of air flowing between the deck and the PV panels; in other words, an increase in the distance between these elements causes an increase in the energy dissipation both by convection and radiation. With the help of STAR-CCM+, a streamlined design process could be established and optimized photovoltaic panels with an increased ratio of energy output over Wp installed could be successfully designed. <

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..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Oil & Gas

Baker Hughes Incorporated (NYSE: BHI) provides reliable, practical solutions when and where our customers need them to lower costs, reduce risk and improve productivity. From the reservoir to the refinery we create value with high-performance products and services to analyze, drill, evaluate, complete and produce oil and gas reserves and then transport and refine the hydrocarbons. For over a century, innovation has been part of our DNA. Baker Hughes was formed in 1986 with the merger of Baker International and Hughes Tool Company, both founded over 100 years ago when R.C. Baker and Howard Hughes conceived ground-breaking inventions that revolutionized the fledgling petroleum era. Since those earliest advancements, weâ&#x20AC;&#x2122;ve never stopped searching for solutions to conquer the next frontier.

The Deeper You Go... The Less You Know Simulation Demonstrates Ability to Improve Deep Subsea Oil & Gas Drilling Performance Dennis Nagy, Vice President, Business Development - CD-adapco

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..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Oil & Gas

RIGHT Streamlines around the drill bit

The key to successful implementation of CFD in drill bit hydraulics is the ability to correlate the CFD results to actual down hole performance of the drill bits Dr. Michael Wells, Director of Research, Baker Hughes

The ongoing push for more producible oil and gas reservoirs is leading the industry into greater offshore depths and harsher environments. The challenge of developing and producing from fields at depths up to 25,000 feet requires workers to operate unproven technology in harsher environments, including greater ambient pressure, lower temperature and different well fluid temperatures, pressures and compositions. Traditional design approaches to developing equipment and systems for shallower offshore wells often donâ&#x20AC;&#x2122;t work effectively in these deeper, harsher environments. Further, the nature of drilling makes it very difficult to diagnose the performance of down hole (in the wellbore) equipment in the field. How can petroleum and marine mechanical engineers move outside their traditional realm of experience to develop new designs that will improve drilling performance in these new challenging environments? To address these difficulties, oil and gas companies and their suppliers are increasingly using computational fluid dynamics (CFD) simulation to optimize the performance of drilling equipment. CFD simulation offers the advantages of providing extensive diagnostic information such as the ability to visualize flows and pressures around the bit under actual drilling conditions. Simulation also makes it possible to quickly and easily evaluate the relative performance of different designs. Dr. Michael Wells, Director of Research for the Hughes Christensen division of Baker Hughes and one of the industryâ&#x20AC;&#x2122;s foremost experts on simulation in oil and gas applications, provides here some examples of how simulation is helping to address a variety of drilling challenges. Optimizing PCD drill bits Dr. Wells has spent a considerable amount of effort in hydraulic optimization of polycrystalline diamond compact (PDC) drill bits. PDC bits typically

have from 3 to 12 blades emanating from the center of the bit outwards. Embedded in these blades are polycrystalline diamond cutters (PDC) which consist of thin diamond wafers attached to carbide backings. The cutters are laid out to ensure that the entire bottom of the hole is cut while promoting bit stability. The region between the blades, called the junk slots, provides a path for the removal of rock cuttings. Commonly, a single nozzle is positioned at the top of each blade that feeds high velocity liquid (drilling mud) through the junk slot to clear loose rock debris from beneath the bit. Various nozzle configurations are possible. Bits are designed with multiple nozzles in a junk slot, a single nozzle feeding two junk slots and with no nozzle at all in a junk slot. Dr. Wells indicated that the first step in constructing simulations of down hole drilling involves the creation of a full, detailed solid model of the bit and the sides and bottom of the hole. The region modeled is a sealed volume element comprising the space occupied by the drilling fluid between the bit and the hole walls and bottom. A realistic bottom hole pattern, created as though generated by the cutters on the bit, is incorporated into the model and the bit is displaced into the rock (hole bottom) by an amount typical for the geological region under consideration. The solid modeling environment is also used to generate text information, blade locations, cutter face centers, nozzle centers and other information that is later used by the CFD model. Realistic operational parameters such as flow rate, nozzle size, rpm and fluid density (mud weight) representative g

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..::FEATUREâ&#x20AC;&#x2C6;ARTICLE Oil & Gas

ABOVE

Figure-8 nozzle used in roller cone drill bit set new field record of 45 feet per hour (fph) compared to previous best of 40 fph (Saudi Aramco).

of the region or application being studied are also incorporated into the model. The goal of the simulation is typically to size, locate and orient the bit nozzles to maximize cuttings transport and minimize erosion. Dr. Wells has developed an optimization process that involves configuring the hydraulics across the bit so that the percentage of the total flow rate that passes through a particular junk slot is roughly equal to the percentage of the total cuttings volume generated by the adjacent blade. â&#x20AC;&#x153;The key to successful implementation of CFD in drill bit hydraulics is the ability to correlate the CFD results to actual down hole performance of the drill bits,â&#x20AC;? Dr. Wells said. Hughes Christensen uses a drilling simulator to tie computed results to actual drilling performance in a controlled environment under representative drilling conditions. The high pressure drilling simulator employs actual drill bits (up to 12-1/4 inch in diameter), under realistic pressures (up to 15,000 psi) drilling actual rock cores to evaluate drilling efficiency and the transport of rock cuttings. Rock cores commonly used are Mancos Shale, Berea Sandstone, Wellington Shale, Crab Orchard, Catoosa Shale, Indiana Limestone, Pierre Shale, Carthage Marble, among others. In some cases, special rock cores are obtained from outcroppings of the formations of interest to particular customers. Historically, a variety of oil and water based drilling muds have been analyzed with having mud weights as high as 16 ppg. Erosion along the face of the bit is also a major concern in a number of fields worldwide. To evaluate erosion rates in drill bits and other down hole tools, Dr. Wells has developed a particle erosion model and incorporated it

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into STAR-CCM+. The process began by performing experiments using a single fluid jet to impinge particles on mild steel and carbide matrix (bit materials) specimens. The tests were designed to measure the erosion coefficient, defined as the ratio of the grams of material eroded from the specimen surface per grams of erodent material impinged on the surface. Dr. Wells has successfully applied this model in wide variety applications. Typically the designer used these predictions to move and orient the bit nozzles to minimize the rate of erosion on the bit surface. While erosion cannot be entirely removed it can be greatly reduced and often directed to less critical features of the bit. Optimizing nozzle exit geometry Dr. Wells has also used CFD to investigate the effects of the nozzle profile and exit geometry on the efficiency of the drilling process. He numerically analyzed the flow produced by several unique, commercially available nozzle designs to identify flow features that might lead to improved bit and bottom hole cleaning. Drilling simulator and field tests were conducted to correlate rate of penetration (ROP) improvements with identifiable flow enhancements brought about by nozzle design. The study concluded that small features built into the exit of a bit nozzle have little effect on the resulting jet. The size of the exit feature is limited by the small diameter of the nozzle body. The smallest features, as used by the Y, star and cross nozzles, tend to disappear in the flow at a distance of roughly one to

..::FEATURE ARTICLE Oil & Gas

ABOVE

Non-optimized (left) and optimized (right) cuttings transport

ABOVE

A successful application of the erosion model: the overall rate of erosion on the surface of the optimised case (right) was reduced by roughly 67% compared to the original case (left)

ABOVE Polyhedral mesh of a roller cone drill bit

ABOVE

Four of the several nozzle exit designs examined in this sudy (clockwise from upper left): a) slot, b) Y, c) star and d) cross

two nozzle diameters from the nozzle exit. Larger features, as seen with the slot nozzle may persist for longer distances from the exit but the flow tends to scale with the smaller dimension (width) and thus the jet decays more rapidly with distance from the nozzle exit. These results suggest that features in the nozzle exit must be relatively large to affect the structure of the jet and thereby the performance of the bit hydraulics. Other nozzles designs were evaluated that either force the jet to swirl about its axis or redirect the jet to some angle with respect to the nozzle axis. The simulations showed the turbulent jets generated by the test nozzles differed only slightly from the standard nozzle. The laboratory drill tests and field results correlated with the simulation by showing no change in bit performance. Using STAR-CCM+, a new Figure-8 nozzle was designed then built to address specific applications where a single bit nozzle was required to provide flow to two junk slots---a scenario typically referred to as split flow. In this environment a single nozzle is directed toward the end of the blade separating the two junk slots. A drilling simulator test was conducted to evaluate the benefit of the new Figure-8 nozzle design. The drill tests were conducted in Catoosa Shale at 120 rpm and 290 gallons per minute (gpm) using 11/32 nozzles. When conventional nozzles

ABOVE

Single Figure-8 nozzle directed toward the end of the blade separating two junk slots

Figure-8 nozzle

were used the drill bit started balling (clogging up with drill cuttings which dramatically reduces performance) at a rate of penetration of 52 feet per hour. When the Figure-8 nozzles were used, the bit did not start balling until it reached a rate of penetration of over 190 feet per hour. Balling is the situation where the reground cuttings and solid particles remaining on the hole bottom tend to adhere to the bit body, particularly in sticky formations such as shales, limestones, and chalks. The configuration using a roller cone drill bit resulted in a new field record at Saudi Aramco. Dr. Wells concluded: “These applications demonstrate that STAR-CCM+ offers the potential for huge advancements in drilling, especially under more challenging conditions. STAR-CCM+ gives design engineers the ability to easily and accurately analyze fluid flow, under harsh realistic drilling conditions making it possible to rapidly evaluate alternatives and provide comprehensive diagnostic information. The method also allows design engineers to optimize the fluid flow around the drill bit during the design phase, rather than after the product has been manufactured.” <

i FOR MORE INFORMATION ON BAKER HUGHES PLEASE VISIT: www.bakerhughes.com

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

::::::EXTREME::::::

WEIGHT LIFTING

ABOVE

Twin Marine Lifter concept

Det Norske Veritas (DNV) was founded in 1864 as a classification society. Today it ranks among the largest in the world, and it provides a wide range of services in various domains. The authors are part of the Technical Consultancy Group in DNV. www.dnv.co.uk

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..::FEATURE ARTICLE Marine

Resistance Calculation for the Twin Marine Lifter Cosmin Ciortan, Kåre Bakken, Det Norske Veritas (DNV)

Twin Marine Heavylift AS (TMHL) is designing the Twin Marine Lifter system for installing and removing platforms. Each of the two heavy lifters has 4 rectangular buoyancy elements at one side, helping to lift the platform (on site) and place it on the bigger transpor t vessel. The buoyancy tanks are a challenge when assessing both resistance and course stability. DNV was called to assess the viscous resistance in calm water, the forces on the buoyancy tanks and course stability.

Transporting the platforms from one location offshore to onshore for dismantling and recycling is a cheaper and more environmentally friendly option than destroying them offshore. Twin Marine conceived a system that achieves this using a Twin Marine Lifter system (TML). The system features buoyancy tanks on one side of the ship, which help lifting the platform by taking part of the weight. The ship is 133m long and 40m wide, with a transit draught of 5.35m. The buoyancy tanks are rather large, with a rectangular section of 10m x 12m. In transit condition, the draught of the buoyancy tanks is 8.9m. Obviously, the presence of large blunt bodies at the side of the ship will have a large influence on the resistance and course stability. Vortex shedding is certain to be an issue for flow analysis. In addition, the interaction between the buoyancy tanks and the hull is another problem to tackle. The simulations were performed using STAR-CCM+. Two grids were used in order to check the sensitivity of the results to grid coarseness, using around 4 and 5 millions cells respectively. Trimmed cells were used, with prisms layers around the hull and tanks and increased refinement in their vicinity.

The prescribed ship motion was advancing head-on, with no incidence angle to the flow. The simulations were performed for velocities of 3, 5, 7 and 10kn. For the 3 and 5kn simulations, the free surface was not considered. The ship and tanks were not allowed to sink and trim; they were considered on even keel. Results The presence of the tanks makes it difficult to validate the results against traditional hulls predictions. It was decided to check the methodology by performing a simulation of the bare hull, without the tanks and with no free surface effects. Therefore, the results refer to the viscous resistance only, and as such can be compared with the ITTC ’57 formula. Even so, as the ITTC ’57 formula refers to a flat plate, a shape coefficient must be employed. The value of the shape coefficient was estimated to be 0.35 for a perfect match with the results. But considering that a typical value for a Very-Large Crude Carriers (VLCCs) is about 0.25 and that the VLCCs bodies in our case are more slender and streamlined than average, the value of 0.35 seems realistic. g

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

TML SYSTEM

MAIN HINGE

HINGE SUPPORT

BALLAST TANKS

SKID WAGON SKID RAILS ON DECK

TELESCOPE BEAM & LOAD POINT

VERTICAL HYDRAULIC CYLINDER

QUICK EVACUATION TANKS

BUOYANCY TANKS

SKID RAILS FOR BUOYANCY TANK FRAMES

BUOYANCY TANK GUIDE FRAME

VERTICAL HYDRAULIC CYLINDER

ABOVE

Schematic of Twin Lifter

The results showed strong vortex shedding due to the tanks and to the flow interaction between them. As a consequence, the individual and total resistance components display a highly irregular pattern in time. The jumps in the curves close to 200s are due to the change of meshes. The most interesting feature is that Tank 1 (the forwardmost one) displays the highest resistance, accounting for about 66% of the total resistance. It is also notable that Tank 2, which is located right behind Tank 1, displays a positive value of the resistance, i.e. it is sucked forward in the wake of Tank 1. Tank 3 gets back to the expected sign of resistance, though its value is low, whereas the resistance of Tank 4 is larger. The time-averaged, stabilized values of the individual and total resistance show a rather regular increase with velocity and confirm the observation that Tank 1 contributes the most to the total resistance and that Tank 2 is sucked forward by Tank 1. The rotation moment is rather large, and increases significantly with the velocity. A quick calculation indicates that at a speed of 7kn, the ship should sail at an incidence angle of about 9 degrees. About 12% of the installed thrust would be required to keep the ship on straight course. A dynamic course keeping is mandatory, considering the quick and irregular oscillations of the vertical rotation moment. Conclusions This case shows that CFD (and STAR-CCM+ in particular) can be successfully used for tackling complex phenomena, with useful results and in a reasonable period of time. The results indicate a periodic pattern of the flow around the hull tanks. The flow is dominated by vortex generation due to the presence of the tanks, and this influences the resistance value for each tank and for the ship. < RIGHT

Resistance and Rotation Curves

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Tank 1 Tank 2 Tank 3 Tank 4 Hull Total

..::FEATURE ARTICLE Marine

ABOVE Free surface around the hull and tanks, 10 kn

ABOVE, RIGHT & BELOW TML Illustration

ABOVE Velocity vectors on the free surface

i FOR MORE INFORMATION ON DNV PLEASE VISIT: www.dnv.com

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

RANS Simulation of Complex Marine Flow Problems [*Reynolds-Averaged Navier-Stokes]

Claus D. Simonsen, Senior Specialist, Hydro and Aerodynamics, FORCE Technology.

FORCE Technology is a global provider of hydro- and aerodynamic consultancy services to the ship and offshore industry. The services cover experimental wind tunnel and towing tank testing plus advanced CFD simulations. In addition to this, FORCE Technology also develops maneuvering simulators and provides training in our full mission maneuvering simulators.

Computational Fluid Dynamics (CFD) is becoming a major element in the consultancy services that FORCE Technology offers to its clients in the marine sector. As the application of CFD to design, evaluation and optimization of ships and off-shore structures in their early development stage increases, and more complex geometries and operations are being considered, a thorough knowledge and a solid experience of the CFD tools-including validation against experiments - is required to meet the present and future challenges related to practical flow problems. To test and demonstrate the capabilities of RANS-based CFD in connection with complex ship flows, FORCE Technology, MAN Diesel A/S and DTU in Denmark have recently been involved in a project under DCMT [Danish Centre for Maritime Technology].

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The goal of this project was to build the complete CFD model of a ship, including appendages and operating propeller, in order to study the flow field, compute the hydrodynamic loads and validate the results against experimental data. Due to the complexity of the problem, the appended hull and the propeller were first modeled individually. Afterwards, the two models were combined by means of sliding interfaces to simulate the entire configuration. All calculations were conducted in model scale. The complete simulation process, from meshing through to post-processing was performed entirely within the STAR-CCM+ integrated environment. For the simulation of the propeller alone, an open-water configuration was considered. In this setup, the propeller is

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

ABOVE

Instantaneous pressure field on the stern region of the hull and on the propeller

advancing through undisturbed water with no hull in front of it. The propeller settings, i.e. advance speed and RPM, were taken from an experimental open-water test to allow direct comparison between CFD and measurement. A polyhedral mesh was used. The flow solver was run in steady mode with the rotation of the propeller modeled using the moving reference frame approach. One of the principle advantages of CFD simulation regards the ability to visualize the flow, which gives the engineer a valuable insight into the performance of the design, not easily available using alternative means. For instance, it provides information about the hydrodynamic loads on the propeller, i.e. the propeller thrust and torque. Comparison between calculated open-water data and data measured in FORCE Technologyâ&#x20AC;&#x2122;s towing tank shows that the computed data agrees fairly well with the measurement.

At the typical operation point of the propeller, both thrust and torque were predicted within 3.4% of the measured values. For the hull alone, the flow was calculated in a traditional resistance test setup. Dynamic sinkage and trim were not predicted, so the model was positioned according to the measured dynamic sinkage and trim position. The speed was taken equal to 1.915 m/s, which corresponds to a Froude and Reynolds numbers of Fr = 0.289 and Re = 7.24 millions respectively. Trimmed cells were used for the mesh. The effect of the free surface was included via the two-phase VOF model available in STAR-CCM+. Comparison between computed and measured data shows that the resistance was calculated within 2.4% of the measured value. To check the grid quality, a grid study on three different grids was made; it showed that the calculated resistance changed by 11% between coarse g

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

and medium grids, while it changed by 1% between medium and fine grids. The fine grid was used for the comparison above. The nominal wake field behind the ship at the propeller plane is important for the design of the propeller and is therefore often extracted from CFD simulations. In this case, the ship is relatively slender, so the bilge vortices - which are normally observed in the centre plane wake - are relatively weak. Consequently, the wake contours are smooth. After calculating the hull and propeller flows individually, the components were combined in order to perform a simulation at the self-propulsion condition. The propeller RPM corresponding to self-propulsion were taken from a previous model test conducted by FORCE Technology. The ship speed was set at 16 knots, corresponding to a Froude number of 0.34. Since the propeller was operating in a non-uniform flow field behind the ship, the simulation was run in transient mode, i.e. time accurate. The propeller was physically rotated by means of a rigid body motion and sliding interfaces. Again, the free surface was modeled using the VOF model. The resistance and propeller quantities were predicted within the same accuracy of the measurement as found in the individual models. A study of the field quantities, i.e. velocity and pressure in the stern region, showed a time varying but periodic flow field while a study of the flow field over time showed that the load on the propeller blades varies with the blade position due to the non-uniform propeller inflow field behind the ship. Furthermore, pressure pulses on the hull above the propeller were observed when the blades passed the twelve oâ&#x20AC;&#x2122;clock position. The post-processing results also illustrates how the propeller accelerates the flow and introduces swirl over the rudder downstream of the propeller. The propeller blade tip vortices could also be traced over the rudder. Consequently, the model provides information which may be useful for rudder design. Conclusion The present study shows an example on how STAR-CCM+ can be applied to solve practical flow problems in the marine industry. Flow visualization gives a valuable insight into the physics of the flow problems. Further comparisons between calculated and measured hydrodynamic forces and moments show that STAR-CCM+ results agree fairly well with measured data, which increases the level of confidence in STAR-CCM+ for its application to the evaluation of design variants in the early development stage. <

ABOVE

Nominal wake field behind the ship at the propeller plane and axial velocity contours

ABOVE

Tangential velocity field in stern region

BELOW

Breaking bow wave

i FOR MORE INFORMATION PLEASE VISIT: www.force.dk

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

RIGHT

Pressure distribution on propeller suction side

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