Tests in Catesby Tunnel offer insights into aerodynamics

The testing used the venue’s distinctive facilities to see in further detail the features behind a vehicle’s aerodynamics, testing drag and resistance in repeatable, reliable conditions.

It is hoped this work will give researchers further insight into how to improve a cars efficiency, such as finding the optimum speed for getting the most out of an electric car battery, or reducing a vehicle’s emissions output.

The first test focused on the drag of one of the University cars and looked at the difference in pressure distribution on the back of the car.

In a statement, Professor of Applied Aerodynamics, Duncan Walker said: “If we were to carry out these tests anywhere else, our results’ validity would be hampered by a series of external influences which are not in our control. Carrying out this work in Catesby’s converted railway tunnel allows us to gain more accurate results as the location allows for endless testing in repeatable conditions. 

“Electric cars are becoming more and more common, and people are anxious about how far they can go on one charge. Aerodynamics plays a key role in that because if you reduce the drag, you can go further – so that’s where our interest lies in this first round of testing.

“This data will also help with those still driving petrol cars in the fact that understanding how to improve a vehicle’s aerodynamic performance can allow us to influence positive design changes to reduce the amount of fuel we burn or how much emissions we are kicking out when driving.”

The second round of testing at Catesby saw academics team up with laser measurement technology developer, LaVision. These tests focused on establishing how a vehicle’s wake changes as its geometry is altered, such as changing the spoiler.

The test works by filling a certain area of the tunnel with thousands of half a millimetre sized helium-filled soap bubbles which are illuminated with a laser. The car passes through the bubbles where high-speed cameras capture how the bubbles move, thereby showcasing the air flow around the vehicle. 

Dr Daniel Butcher, senior lecturer in Applied Fluid Mechanics, said: “Similar testing has been around for some years but how we are using the technology is what’s distinctive. We are seeing the vehicle pass through the light sheet where, typically, you’re in a wind tunnel where the vehicle is static and the air flows over it – so that’s the key difference and the benefit of having the facilities of Catesby available to us.

“Another advantage of conducting these tests in this way comes in the form of being able to measure downstream of the moving vehicle – something that’s almost impossible to do if it’s static. It allows us to measure 10, 20, 30 car lengths after it’s passed through to ascertain what this means for when we’re on the road and around other vehicles.

“These are real-world tests, testing the real aerodynamics around a real car in real and repeatable conditions. The whole test is really a development of the measurement technique but the data we gather here is going to help us validate our research and to better understand where the sources of drag comes from. We can then share this information with vehicle manufacturers to allow them to build more efficient and aerodynamic cars.”