This is a prime example of interference drag.
Aerodynamic Safety Precautions:.
The high speeds at which racecars travel at create dangerous scenarios for the drivers and fans. Car designers use fluid mechanics to lessen the effect of cars leaving the ground during racing. Racecars are designed to stay on the ground as long as they are moving forward, but if they are turned sideways or backward, they can generate a lot of lift due to the design. .
To reduce the chances of cars getting airborne, engineers have developed several extreme anti-lift devices for use on racecars. Roof rails, side skirts and recessed edges on the right side windows are passive aerodynamic safety features on stock cars. Rails are thin vertical strips running front to rear along the edges of the roof. .
Figure 6 (Typical Motion of Spin).
In order to prevent lift, air has to be moving slowly. The sharp protuberances of the roof rails break up the streamlined airflow and reduce unwanted lift. .
Figure 7 (Roof Rails).
Skirting around the lower edge of a car's side keeps high-pressure air from getting under the vehicle if it is moving sideways, lessening the tendency to spin, or fly. Because racetracks turn left and cars tend to move to the right when they go out of control, the right windows are recessed, that gives the window an edge to interrupt streamlined air when a car turns right, producing the same effect as roof rails.
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Figure 8 (Safety Precautions).
Staying Grounded:.
• SPOILERS: A metal strip that helps control airflow, down force (the pressure of the air on a car as it races), and drag (a resisting force in a car's air stream). The front spoiler or "air dam" is underneath the car's front end near the axle; the rear spoiler is attached to the trunk lid.
• ROOF RAILS: Airflow over a smooth surface can create lift. These strips are designed to break up streamlined airflow across that lift.
• SIDE SKIRT: This skirting keeps air from getting under the car if it moves sideways.
