EU Research Winter 2016

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Creating Efficiencies in Aircraft Design Two EU funded projects, ALPES and AeroGust, coordinated by the University of Bristol, are developing new methods to speed up and improve the accuracy of key processes involved in the design of more environmentally friendly aircraft. The aim is determining how loads, such as those caused by gusts of wind, interact with aircraft. Professor Jonathan Cooper explains the methods and the objectives of the projects that will lead to more efficient and cost effective aircraft designs A key job in the design of an aircraft is to make sure it can cope with the stresses arising in flight or from manoeuvres on the ground. For instance, when an aircraft is buffeted by strong winds, this will affect all the parts of the plane’s structure as well as impacting on passenger comfort, so calculating the way that each component and also the entire aircraft reacts to gusts is essential knowledge before a plane can be built. “Say you’re flying and the pilot says, ‘buckle up, we’re going through bumpy weather’,” explains Professor Cooper, illustrating the challenge. “This is an example of loads, in this case due to socalled gusts or turbulence. Aircraft need to be designed to cope with those loads and also those resulting from manoeuvres as a plane flies around, or during take-off and landing, turning and braking. So the loads department, in conjunction with the aerodynamicists, will compute the hundreds of thousands of different loads that might be encountered during a flight, and stress calculations then need to be performed for many different parts of the aircraft.”

A massive computation The computational task has to account for the effect of loads on every element of the aircraft design, in every possible situation. In practical terms, this means calculating all possible combinations of fuel and passenger weights in different situations such as flying high or low, or flying fast or slowly. The number of variables is vast. From these calculations it is possible to reveal a complete picture of all the stresses on the structure of the plane and to determine the critical cases. Only when

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Aircraft flying in a vertical gust field. you have that information, can you understand where you might be able to make adjustments in the design, such as making parts thicker where the stress is too high, for example. “Some parts of the aircraft will be most affected by gust loads, and others by landing, or turning on the runway and so on, and these critical cases are determined from all the simulations. Once you’ve done one entire set of simulations, the structures department can work out where they may be able to change the structure in some way to make it safer and also lighter in weight – and then the process starts over again.” The problem is, as it takes so long to process each set of variables, the time and expense to rethink major aspects of design may not always be practical. It would be hugely beneficial therefore, if the time and effort it takes to compute loads early on in the design phase, was made more efficient. New approaches need to be explored to see where

efficiencies can be made, whilst maintaining accuracy. This is where the five researchers in the ALPES project come in, working on solutions that will streamline processes whilst improving accuracy. The engineers are all engaged in PhDs, conducting new research, whilst dividing their time between the University of Bristol, Siemens in Belgium and Airbus. “We are doing some brand-new science but we are doing it with an industrial focus,” said Professor Cooper. “We are doing things that Airbus are interested in, that are going to help improve their aircraft designs. It takes 8-10 years to develop a new design but if we can bring that down to five years, you get a tremendous competitive advantage. So we are looking at creating efficiencies – if we’ve got 500,000 different cases that we need to look at and we can reduce that to 50,000, or even 5000, we immediately speed the process up dramatically.”

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