Yellow Flag Caution: Mind-Numbing; Read at Bedtime


Racing Physics: Aerodynamic Design; Driver Aggravation


The ideology which allow aircraft to fly are also pertinent in car racing. The only dissimilarity being the wing shape is mounted upside down producing downforce instead of lift. The Bernoulli Effect means that: if an air (gas or liquid) flows around an object at different speeds, the slower moving air will exert more pressure than the faster moving air on the object. The object will then be forced toward the faster moving air (AERO PUSH). The wing of an airplane is shaped so that the air moving over the top of the wing moves faster than the air beneath it. Since the air pressure under the wing is greater than that above the wing, lift is produced. The shape of the NASCAR racecar exhibits the same attitude. The nature of the bodywork combined with the outer arrangement is alike to an upside down airfoil. The air moving under the car moves faster than that above it, creating downforce or negative lift on the car. Airfoils or wings are also used in the front (lower dam) and rear of the car in an endeavor to produce more downforce. Downforce is essential in maintaining soaring speeds through the corners and forces the car to the track. Light planes can take off at slower speeds than a ground effects race car can generate on the track. In addition the shape of the underbody, combined with the outer configuration (an inverted wing) creates an area of low pressure between the underside of the car and the racing surface. This sucks/vacuums the car to road which results in superior cornering speeds.


The total aerodynamic put together of the race car is emphasized now more than ever before. Teams that plan on staying competitive use track testing and wind tunnels to expand the most proficient aerodynamic design. The center of attention of their efforts is on the aerodynamic forces of negative lift or downforce and drag. The relationship between drag and downforce is especially important. Aerodynamic improvements in wings are directed at generating downforce on the race car with a minimum of drag. Downforce is necessary for maintaining speed through the corners. Unwanted drag which accompanies downforce will slow the car. The efficient design of a chassis is based on a downforce/drag compromise. In addition the specific race circuit will place a different demand on the aerodynamic setup of the car.

A road course with low velocity corners requires a car setup with a high downforce put together. A high downforce tie together is necessary to maintain speeds in the corners and to decrease wear on the brakes… The rear wing is made up of sections that maximize downforce.


The speedway setup looks much different. The front and rear wings are almost flat and are used as stabilizers. The major downforce is found in the shape of the body and underbody. Drag reduction is more critical on the speedway than on other circuits. Since the drag force is proportional to the square of the speed, minimizing drag is a primary concern in the speedway setup. Effective use of downforce is especially pronounced in high-speed corners. A race car traveling at 200 mph. can generate downforce that is approximately twice its own weight.


Generating the necessary downforce is determined in three specific areas of the car. The ongoing test for team engineers is to fine tune the airflow around these areas.
1. Front lower dam assembly
2. Chassis
3. Rear wing assembly


Some common terms seen in many discussions about the COT concerning the Aero Push and the ability to Pass or lack thereof.


• Aerodynamics: The study of the motion of gas/air on objects and the forces created.
• Airflow: The movement of air around the chassis of the race car.
• Bernoulli Effect: states that the pressure of a air (liguid or gas), decreases as the air (liquid or gas), flows faster.
• Cd: Drag coefficient or Coefficient of Drag. It is determined by the shape and smoothness of shape of the object. In this case the car.
• Chassis: Refers to all mechanical parts of the car attached to the structural frame.
• Computational Air Dynamics (CFD): Equations that are known are programmed into computers. The computers provide solutions to the problem of external airflow over vehicle shapes. The body of the configuration and the space surrounding it are represented by clusters of points, lines and surfaces; equations are solved at these points. CFD is divided into three steps. Grid generation, numerical simulation and post-process analysis.
• Downforce: A vertical force directed downward, produced by airflow around an object. Downforce is generated from the front and rear wings and the venturi tunnels on a ground effect car.
• Drag: Force acting on an object in motion through a air (in this case air) in an opposite direction to the objects (chassis) motion, produced by friction.
• Ground Effects: Downforce created by a low pressure area between the underbody and the ground, and downforce created by the front and rear wings.
• Lift: The upward reaction of an aircraft to the flow of air forced over the shape of the wing (airfoil). The front and rear wings of ground effect cars are shaped like inverted wings to create downforce or negative lift.
• Turbulent: Turbulent airflow is when the air streamlines break into eddies and complex changing patterns. This can cause unstable forces on an object. As the airflow moves from the front of the car to the rear it becomes turbulent.
• Venturi Effect: Air speed increases when the air is forced through a narrow or restricted area. The increased speed results in a reduction in pressure. The underbody venturi is shaped to create a low pressure area between the road and chassis which creates downforce.
• Vortex: When an air rotates around its own center, it is called a vortex. Turbulent flow is made up of many little vortices.


I told You it was going to be a rather “*DRY READ*” to say the least,,, but for those who want to know what all the ‘*HEE HAWING*’ is about,,,, this is it…


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