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Greenpower PitStop Chat: An introduction to Aerodynamics

22 June 2020

Author: The Greenpower Team

Greenpower PitStop Chat: An introduction to Aerodynamics

Our recently launched PitStop Chat series aims to give an insight into different elements of the Greenpower challenge. From extracting more potential from your car, to gaining the confidence to approach local businesses for sponsorship opportunities, we hope our PitStop Chats will prove informative.

The first topic we delved into was the complex field of aerodynamics. We asked our CEO Paul van Veggel and Trustee, aerodynamicist and former participant Nash Vracas to join us to share their expertise on what it is and how to use it to your advantage.

Here are our key takeaways:

What is aerodynamics?

Nash: “Aerodynamics is the study of the movement of air around an object. There’s lots of different applications of this, from aircraft, to motorsport and automotive, to building structures, and even in sports! Athletes’ equipment and clothing can affect their aerodynamics.”

Paul: “You can study aerodynamics in a number of ways: you can observe it, you can simulate it on computers through computational fluid dynamics (CFD), and you can study it using tools like wind tunnels. But you can also do it yourself on a track, using just your Greenpower car.”

Why is aerodynamics important in the Greenpower challenge?

Paul: “Aerodynamics really has an impact on how far a Greenpower car can go, and how efficient it can be. You may not think it is going very fast but the challenge is a game of small margins; it’s all about getting to the end, going a further distance than anybody else. Even the smallest of changes can make that difference. If you have two cars that are very competitive mechanically and one has better aerodynamics, it will stream ahead of the other by the end.”

Nash: “With a Greenpower car, you’ve got three forces acting on it. You have forward propulsion from the motor, you’ve got resistance between the tyres and the road and aerodynamics pulling you backwards. In Greenpower cars, the total resistance from aerodynamics is about 75%, so it’s quite significant. You also have to look at it as a holistic system – if you have two cars with the same aerodynamics, but one is considerably heavier than the other, the lighter car will perform better. If you’re ever in the situation where adding some material that will add a couple of extra grams in weight but will result in a reduction of drag, then lean towards that.”

Should a team focus on the nose or the tail of the car?

Paul: “It depends. It’s really hard to perfect one part of the car without affecting the rest of the car. If you have a blunt nose and a pointy tail, the car won’t be very good. If you have a messy tail and a beautifully sculptured nose, it also won’t be very good. Aerodynamics is about the entire shape, not just the front and the back of the car, and how the shape of the car changes over the entire length of the car. There isn’t one particular answer, and it’s about making the best shape around your space constraints where you can’t go any smaller.”

Nash: “As rule of thumb, we tend to work front to back, but you can’t just look at one area over another. Generally, a nice, smooth nose helps with flow attachment – where the airflow sticks to the surface of the car. You may get to certain points where the design of the car means the flow no longer wants to stick to the car, and that’s when we get separation. You can actually feel this if you touch the A pillar of a car when you are driving – you might suddenly stop feeling the air on your hand. The overall shape is important to optimise air flow, and that’s why on the Greenpower grid you see so much variation in design.”

Paul: “You won’t get it right first time, and it won’t be perfect. You will need to start at the front and work to the back, analyse what you have got, and iterate it. That’s the only way you will make a good car.”

Nash: “It’s a long process, but it is worth it!”

You can watch the full PitStop Chat with Nash and Paul on our YouTube channel, as well as enjoy the other videos in the series.