VWT - Greenpower Car Aerodynamics
So why do we need to look at the aerodynamics of a Greenpower car ? So that you can make it go faster and win races :)
With the Greenpower challenge you have a fixed amount of energy within the batteries to last a race. This allows a certain average power level to be used throughout the race. So the only way to go faster is to improve the efficiency of the car.
It is important for engineers to understand the science aspect of their designs in order to understand what is needed and how best to optimise the design for the environment it is designed to work in. The engineer will at least use basic mathmatics in the design process and quite often farily sophisticated mathematics in calculating parameters and often in simulating the design to test and optimise its function prior to actually building an example.
The following technical information gives some details on the science and mathematics of a Greenpower car: See: http://www.greenpower.beamweb.co.uk/files/TechnicalInfo
In general for a typical Greenpower car, after the motor about a third of the energy goes into overcoming rolling resistance and two thirds overcoming aerodynamic drag. Aerodynamic drag increases with the square of the cars speed and so as you go faster it becomes increasingly important. So although having a lighter Greenpower car will help as it reduces rolling resistance, it is the aerodynamics that play the most significant part in making the car go faster.
Aerodynamics the Core Things
The front: When the car moves through the air it has to push the air aside. This creates a higher pressure on the front areas of the car that holds it back.
To improve the overall car the frontal area (how big the car looks from the front) has to be reduced as much as possible. This is the only real way of reducing the frontal pressure drag. However reducing it can make the cars shape less aerodynamic so its not clear cut.
The rear: As the air comes back together again at the rear areas of the car it can separate from the cars surfaces and create a low pressure "vacuum" area that holds the car back.
This is the area where the shape of the car has the most significant impact and where most work can be done. Getting the air to come back together quickly and smoothly is the target. Long, smooth pointy tails is the way here. You should reduce sharp changes to airflow by reducing the angles of airflow change to the minimum.