The basics of Aerodynamics
How does a racing car work and how does it stick to the ground?
Downforce, also known as downward lift (opposite to the lift involved in the aerospace field) is the force of air that pushes the car to the ground, increasing the vertical tyres load and creating grip. The main goal is to have a difference in speed over the top and bottom surfaces of a component, since an increase in speed causes a reduction in pressure. As a consequence, this causes a difference between the upper surface - where, thanks to the geometry of the car, higher pressure is produced - and the lower surface (low pressure) of the car as it moves through the air.
The “negative side” of Downforce
However, downforce comes with a “penalty”: drag - a force that resists the motion of the car. This force also “wears down” some horsepower, as higher velocity requires more horsepower to overcome it. Thus, the main goal of any aerodynamic department is to build a car that can extract the maximum downforce with a minimum production of drag. Aerodynamic balance and efficiency are the key.
As we can assume from the formulas: Downforce= Cl 1/2 pv^2
Drag= 1/2Cd p V^2 A
It’s clear that the more you increase speed, the more downforce and drag you generate.
An aero setup varies depending on the track, since aerodynamic performance changes as conditions change. Too little downforce and the car will be slow in high-speed corners; too much downforce, and the car will be slow on the straights. So, the aim is a good balance between front and rear of the car.
How to produce downforce on a race car
Some of the most common components that produce downforce on a car are the body shape and the use of wings, which - thanks to their profiles- increase the general load.
Coming to the Dallara DW12 (current IndyCar), the introductions (aero kits) taken at the beginning of 2018 were all directed toward exploiting more downforce from ground effects rather than from the front and rear wings. It is fair to say that generally, racing car use ground effects, but some use them more effectively than others.
What is ground effect and how does it work?
Ground effect helps to reduce the pressure that is underneath the car while extracting airflow, thus gluing the car to the track. This decision was made to ensure cars could overtake each other in the race, reducing the dirty air that was caused by close-following. Indeed, with a greater angle of attack on the front wings (as seen in the formula the more aerodynamic surface is exposed to the air, the more downforce is generated), cars would find it more difficult to overtake since turbulent air would create instability on the wings. As can be easily understood, ground effect causes less drag compared to wings, so it produces power with no additional cost. Then, to reduce turbulence issues and improve the show, IndyCar decided to introduce ground effect cars to reverse its downforce production.
