Aerodynamics, Why are they important?
Aerodynamics is the study of gasses moving over and around a body in motion. This airflow also will affect the body’s movement through the flow. Aerodynamics is used on road vehicles in order to make them safer and maximise fuel efficiency. Aerodynamics is more commonly used in race car designs because of the higher speeds that the vehicles do. In race car design, the same principles of aerodynamics are applied, just with a slight twist. The shape of a race car chassis is remarkably similar to an inverted aircraft wing. When a wing is inverted it creates downforce (negative lift) instead of lift.
Road Car Modifications
Many modifications can be made to a production car in order to raise their aerodynamic efficiency. These modifications can range from being fairly in-expensive, to extremely expensive. The modifications that can be made are listed and explained below.
Spoiler
A spoiler is a device that slows and collects air causing it to stand still. The spoiler creates an area of high pressure replacing the normal low pressure over the rear of the car. This helps reduce the pressure difference between the top and bottom of the car in turn which in turn creates downforce and reduces lift. Spoilers have one major drawback, they increase drag.
Airdams
The easiest way to stop air stagnation under the vehicle is to block the air going there. This is done by means of an “Airdam.” An airdam is a spoiler placed at the front of the car at the bottom of the bumper. Airdams also collect air thus increasing drag although by stopping the drag created by the stagnation under the car, the airdam actually reduces the overall drag. It also creates a pressure difference between the top and the bottom of the front of the car creating downforce giving increased cornering grip and steering response.
Splitters
A splitter is very similar to an airdam in the way it works. Splitters are normally found on the bottom of the airdam. The splitter utilises the stagnant air caused by the airdam to create downforce.
Sideskirts
Side Skirts are needed on a car because the low pressure under the car won’t last long if air can just enter from the sides. Side skirts block airflow entering the underside of the car. The skirts are found between the front and rear wheels on each side of the vehicle.
Undertrays
Undertrays are a great way to reduce pressure under the vehicle and overall lift. Undertrays will not work alone. They must be used in conjunction with side skirts, airdams, and splitters.
Airfoils
Airfoils are the most common of devices for producing downforce. Airfoils (wings) use a pressure difference in order to create downforce similar to the way an aircraft wing works although instead of creating lift as an aircraft does, an airfoil creates negative lift.
Diffusers
Diffusers create the most downforce of all the modifications talked about. They create so much downforce that a lot of governing bodies for motorsports have banned them completely.
A diffuser is a device that expands the directions of the airflow thus increasing the pressure of the flow. The optimum angle for a diffuser is around 9.5° above horizontal. A diffuser located at the rear of a vehicle will also serve as a pressure reservoir to fill the void at the back of the car. Not only do diffusers create massive amounts of downforce but they can also significantly reduce drag.
