Interior Storm
To the everlasting frustration of meteorologists, it remains a fact that the weather will never be truly predictable. But at an advanced wind tunnel research facility near Paris, a team of Nissan technicians has a special power at their fingertips. With the flick of a switch, they're able to precisely control the forces of nature – everything from a miniscule breeze right up to the winds in the most powerful tropical storms.
Their goal? To perfect the art of automotive aerodynamics.
"The objective is to reduce the aerodynamic drag of the vehicle, which basically means making it easier for the car to cut through the air," explains Sarwar Ahmed, Aerodynamics Engineer at Nissan Europe.
Far from being something that's barely there, air can actually put up a huge amount of resistance. In fact, aero forces increase exponentially with speed, meaning in turn the car has to work exponentially harder to maintain forward motion against the oncoming air.
For electric vehicles, reducing drag is even more crucial. On long-distance high speed driving, without aerodynamic design "the vast majority of your battery energy would be used simply to push through the air", explains Sarwar.
Sculpting a shape
As a result, every millimetre of a car's design needs to be meticulously evaluated to ensure the its shape is as streamlined as possible. The best place to test this? In the giant wind tunnel.
"During the early stages of vehicle development, Nissan will have more than one styling concept," says Sarwar. "We use the wind tunnel to provide feedback on what initial features or concepts work better or worse for aerodynamics." This begins by defining the proportions or the general shape of the vehicle, a stage where "there can be quite significant changes," adds Sarwar.
But it's not just the overall shape that impacts how aerodynamic a vehicle is. Sometimes, refining just one specific feature can lead to major improvements. For example, "The wheels and tyres contribute around a third of the vehicle drag," says Sarwar. "But a relatively small part - like wheel deflectors - can guide the flow of air around the tyres". Similarly, "the grille shutters that close off air going into the motor bay make a massive improvement to the drag."
One feature that is often adapted from wind tunnel testing is the positioning of the wing mirrors on each model. Through computer analysis of airflow over the test model, the team can identify where vortex shedding (areas of low pressure) around the mirrors is strongest, which can have the effect of pulling the car back. To mitigate this on the all-new electric Nissan Ariya, for example, this means "the mirror location has been flag mounted, instead of sail mounted," observes Sarwar. "This is better for aero acoustics too!"
Finely Tuned, Ferocious Power
To capture its sensitive scientific data, the wind tunnel is purposely built for its field of physics. A moving ground allows the vehicle's wheels to rotate to simulate driving on a road, while the floor within the wind tunnel also sucks air in front of the car to reduce the boundary layer growth, further increasing the accuracy of measurements. Even more impressively, "The entire thing sits above a giant balance below ground that can detect the smallest of forces, and torque measuring in 6 degrees," explains Sarwar.
Yet despite these delicate features, the wind tunnel boasts some serious power. When at full throttle, the turbine's huge blades can generate a sustained windspeed of up to 240km/h – that's equivalent to a powerful Category 4 Hurricane1 – all contained within 4 walls! Although, as Sarwar admits, "that is a bit excessive for us. We tend to only need to test at 140kph!"
While testing at such speeds can be a lot of fun, it all come back to a serious purpose: saving energy output from the vehicle, thereby cutting emissions in cars with combustion engines or helping EVs go further. As the world switches to electric, Sarwar points out that "aerodynamic development and testing will only have to increase, to make sure our customers get the best EV range they can."
The new Nissan Ariya puts this ethos at the heart of its design. Following wind-tunnel testing, its sculpted shape means it is expected to be the most aerodynamically efficient model in all of Nissan's crossover lineup. So, in the race towards greener personal mobility, you can be sure that more Nissan models will be tested against the storm-force power of the wind tunnel.
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Related: Ariya expected to be the most aerodynamic Nissan crossover ever built |
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1 Measured on the Saffir Simpson scale
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