Wind tunnel

Shooting the breeze in the Lexus wind tunnel

Automotive aerodynamics is a science that helps to perfect the relationship between airflow and a car’s noise levels, dynamic characteristics and fuel economy. Lexus is a global leader in this field, a fact that is emphasised by an aerodynamics laboratory at the manufacturer’s research and development headquarters in Japan’s Aichi Prefecture.

Opened in 2013, there are many things that impress you about this facility, not least of which is its size. The lab’s enormous wind turbine drives air through a looping, 260 metre tunnel at up to hurricane speeds. The tunnel itself is a cavernous space, 22 metres from floor to ceiling, and venturing inside makes you feel like you’re standing inside a hollowed-out skyscraper.

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At one section of the tunnel, the wind stream enters a testing room where Lexus engineers analyse airflow around key areas of a vehicle. Sometimes tendrils of smoke are used to more effectively evaluate the efficient passing of air around or through components such as the wheels, bumpers and underbody.

“The most important function is to generate a very steady flow of air towards the car, so we can understand precisely how air travels around it,” said Toshiyuki Murayama, group manager of thermal management and aerodynamics at Lexus.

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To better direct this airflow, the tunnel’s continuous loop is punctuated by metal slats (see above), which are slanted at a precise angle to smoothly guide air through the facility. “We had the structural details fine-tuned,” commented Murayama. “So the layout of the walls, the selection of materials, and location of vents and nozzles, all help make this lab one of the most reliable research facilities in the world.”

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Carry on walking around the facility and you eventually find yourself stood on one of a number of turntables, a tool Lexus also uses at its futuristic design house.

“Design and aerodynamics have much in common,” Murayama revealed. “Even a tiny exterior part of a car can change the flow of air around the body – for better or for worse – so it is key that one of our most advanced laboratories is just a stone’s throw away from the design division.”

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How do engineers physically test a car aerodynamically? First, a vehicle is wheeled onto a turntable weighing scale in the central testing room. “Weight distribution to each of the four wheels changes depending on how the wind travels around the car. This affects its aerodynamics, so we closely monitor that too,” explained Murayama.

The turntable also doubles as a rolling road, with belts for each wheel that allow the vehicle to reach top speed without moving forward an inch.

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Next, the wind turbine begins to rotate, generating winds that can reach up to 155mph. Safely shielded from this punishing rush of air is a team of engineers monitoring every tiny aspect of the car’s behaviour, tweaking, reacting, adjusting and fine-tuning to make it more aerodynamically efficient.

It’s not just airflow the engineers are studying – noise-reduction testing is also a major element of the team’s research. “We have an array of microphones on the ceiling and walls that helps us monitor noise on the computer screens,” said Murayama.

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One of the latest production models to have received the full benefit of this new laboratory is the Lexus RC F. Indeed, chief engineer Yukihiko Yaguchi has proudly described the car as being “honed to perfection in the wind tunnel.”

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By simulating road conditions at the laboratory, Lexus can get immediate feedback in the development of its cars without having to leave the premises. Reacting to these results, innovative prototype parts, such as small stabiliser fins made with onsite 3D printers, can be quickly and easily put to the test.

“Every part of the car is designed within the margin of a millimetre,” Yaguchi explained. “We go through every possible layout of the ducts or the sizing of aerodynamic parts. All the details and conditions must be taken into consideration. It is no easy job.”

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