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Gone with the wind tunnel: auto industry warms to simulation

Michael Nash speaks to Ales Alajbegovic, Vice President, Ground Transportation Applications at Exa Corporation, about the growing demand for and capability of simulation in vehicle design

Using simulation tools to aid vehicle design processes is not a new phenomenon. But as the software becomes increasingly sophisticated, a growing number of OEMs could replace existing testing methods with more efficient and accurate simulation tools. Exa Corporation, a developer and distributor of engineering simulation software, believes that a growing number of companies are beginning to realise the advantages of using simulation tools when it comes to the vehicle design process.

Busy times ahead

According to Ales Alajbegovic, Vice President, Exa, the company’s simulation software is in high demand, and he predicts further growth in the future. “We are getting busier because a growing number of OEMs and Tier 1 suppliers are using sophisticated simulation tools at an increasingly early stage in the design process,” he explained. “One of the big generators of this push is the fact that the OEMs are recognising the product and cost benefits of early design optimisation.”

Exa TESLA streamribbonsOver the past decade, simulation software has become a standard design tool used in the automotive industry, Alajbegovic adds. “There is still a wide range of differences between automotive companies. There are those that have made computing power a part of their strategic capability, and those that are still lagging behind. But many are being progressive in using computations, and are getting to the point where the models and algorithms of the simulation software they use can predict a wide range of things from a very early stage of the design process.”

This, he says, is critical to save money and reduce time in the design process all the way up to vehicle production. “Designing a car or truck entails an incredibly complex system, and every single part, no matter how big it is, will affect the aerodynamic performance of the entire vehicle in a non-negligible way. Simulation is so important to control this, identify early on, and discover how the system is going to behave. It is the key enabler for the new companies entering the automotive market that don’t have existing infrastructure and design processes in place. Tesla Motors is a good example.”

Do OEMs really need to use simulation tools during the design process, or can they rely on other forms of testing to help identify issues and discover how the vehicle performs?

The main offender

Wind tunnels have played a key role in the development of vehicles for generations. However, as OEMs strive to represent real world fuel economy and emissions figures with their models, these early representations are proving inadequate.

“When it comes to aerodynamics, there are many improvements still left on the table when using only a wind tunnel as the design tool,” explains Alajbegovic. “The wind tunnel is still only an approximation of the reality, and the conditions it attempts to mimic can be a far cry from what the car really experiences on the road.”

The issue of the gap between real-world emissions and efficiency figures and those obtained during lab tests was taken to a new level when the Volkswagen emissions scandal broke. Since then, many OEMs have come under the microscope with their models being tested in and out of the laboratories.

Using wind tunnels to approximate design can add uncertainty to the gap between real-world and lab test figures, says Alajbegovic. “There are all these different parameters that aren’t represented in the wind tunnel, like the road conditions, for example. Traffic turbulence, wind gusts and rotating tires can have a big impact and wind tunnels cannot properly re-create them. Also, every wind tunnel is different, so one vehicle tested in ten different wind tunnels will produce a big variety of results. Which one is the right one?”

For this reason, he thinks that wind tunnels should not been seen as a design tool. “They merely provide approximations in a controlled environment that you’ll never get on the road. And we have to be as honest as we can in the representation of real-world figures for the benefit of the end customer.”

Exa TeslaIn order to accurately represent the aerodynamics of vehicles during design, and subsequently the fuel economy and emissions figures, some OEMs are using simulation tools as well as wind tunnels, “but using them in different ways,” Alajbegovic explains. “For example, the wind tunnels are very useful in the validation of simulation tools.”

Furthermore, one of the big bonuses of software is that simulations can easily explore large variations in vehicle geometry. “This, in conjunction with the modern optimisation methods, can help find design solutions that are not practically possible using physical prototypes,” he adds. “Companies that continue to spend a lot of time and money on wind tunnels and prototypes without taking advantage of simulation to reduce the amount of experimentation as part of the design process simply won’t survive.”

Alajbegovic believes these could be the reasons behind the Jaguar Land Rover (JLR) decision to exclusively use simulation tools in the aerodynamic design of its XE released in 2015. “There were no physical prototypes built and the predicted aerodynamics performance was validated on the first production car,” he says. “It is interesting that Jaguar XE also achieved the lowest aerodynamics drag of any previous Jaguar car.”

Push comes to shove

Returning to the global trend of growing demand for simulation tools, Alajbegovic describes two factors that are having a big impact on OEMs. “The first is model proliferation, because there is clearly a demand for more niche vehicles with differentiating designs. The industry has learnt to have common architectures underpinning these vehicles to save on costs, but then the rest of the vehicle must be unique.”

Exa Jaguar XE simulationInstead of subjecting all these different designs to tests in wind tunnels, Alajbegovic feels it would be much quicker and simpler for OEMs to use simulation tools.

“There is also the regulatory side of the equation,” he continues. CO2 and fuel economy regulations are also prominent considerations in vehicle design, he says, and as a result, one of the company’s largest growth drivers.

Alajbegovic thinks that the 54.5mpg target in the US and 90g/km of CO2 in Europe will be hard to meet, but is confident that simulation can play a significant role in helping OEMs.

Looking ahead to the future, he believes simulation tools can help companies improve vehicle aerodynamics and fuel economy. “A 2% aerodynamic improvement gives you 1% fuel economy improvement. Achieving a drag coefficient (Cd) of 0.20 is the new target, which I think will be achieved in the next two to five years. Further aerodynamic drag reduction will have a dramatic affect on the design of vehicles.”

This article appeared in the Q1 2016 issue of Automotive Megatrends Magazine. Follow this link to download the full issue.

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