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Aerodynamics of Race Cars. Joseph Katz. Department of Aerospace Engineering , San Diego State University, San Diego, California ;. Race car performance depends on elements such as the engine, tires, Joseph Katz; Published ; DOI/webtiekittcenve.cf Race car. Race Car Aerodynamics: Designing for Speed (Engineering and Performance). Home · Race Car Performance) Author: Joseph Katz DOWNLOAD PDF.
Joseph Katz , has discussed typical design tools such as wind tunnel testing, computational fluid dynamics, and track testing, and their relevance to race car development. This review briefly explains the significance of the aerodynamic down-force and how it improves race car performance.
Review Computational Fluid Dynamics CFD is a computer-based technology that studies the dynamics of all things that flow.
In Formula One racing, CFD involves building a computer-simulated model of a race car and then applying the laws of physics to the virtual prototype to predict what the down-force or drag may be on various components of the car or how the car will respond in various wind conditions, changing environmental conditions or on different road surfaces.
Steps in Solving CFD Problem On the basis of important features of the problem to be solved, the basic procedural steps are given below. So the flow would definitely be a turbulent one at the front wing surfaces.
It has dimensions of L2 T-2 , e. It becomes negative i. Modeling First of all, a model without endplates has developed to check endplates as flow deflectors. Then three models have been developed from the Basic Model with optimum angle of attack by attaching additional down-force productive plates to the endplate. Figure 1 CAD Model without endplates 3.
Basic Models This primary design sets a Basic Model of the front wing.
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Point of the front wing on the leading edge is 950mm, from the wheel centre as per the regulations. Base plane is taken at a height of 100mm from road. B1, B2, B3, etc with change in angle of attack have been developed. To deflect the flow from wheels so as to reduce drag, a vertical wing endplate is introduced. Thickness of endplate is 32mm. It is assumed that the flow should remain attached on the upper surface of the wing.
Another model has been created with a plate attached to the endplate.
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Mesh Requirements The car front-body is symmetric about a central vertical plane, thus only half portion is used for analysis. Remaining portion has been used for flow analysis.
Figure 5 Boundary conditions of meshed model 5. Convergence of solution for all models is obtained after about 150 iterations. The rapidly developing automotive industry followed and one of the most signicant designs of that era is the 1924 Tropfenwagen droplet shape in German described by Hucho 1998, p.
Note that in automotive applications the vehicles frontal area is used as a reference for the drag and lift coefcients.
Only four years later, in 1929, the Opel-designed rocket race car was the rst to employ wings see vehicle description in Hucho 1998, p. Those wings extended sideways, oriented at a negative angle of attack to create downforce. This major innovation was completely ignored and it took another 35 years to fully realize the signicance of this principle.
To explain the signicance of aerodynamic downforce on race car performance, the tire characteristics must be discussed briey rst.
The motion of air around a moving vehicle affects all of its components in one form or another. Engine intake and cooling ow, internal ventilation, tire cooling, and overall external ow all fall under the umbrella of vehicle aerodynamics. The present discussion, however, focuses on the effects of external aerodynamics only, and ad- ditional information on internal ows can be found in publications such as Hucho 1998, ch. As mentioned earlier, the discussion on race car aerodynamics cannot be complete without briey discussing tire characteristics.
Although it is clear that airplanes y on wings hence the signicance of aerodynamics , the fact that race cars y on their tires is less obvious and requires additional clarication.
Inset depicts denition of side slip. For example, Figure 1 describes the forces acting on a side-slipping tire on the road.
race car aerodynamics designing for speed by joseph katz
The right-hand side schematics depict the three forces e. In this case the vehicle is heading into the -x direction, but due to a positive side force could be inertia due to cornering it slides at an angle , as shown in the gure.
Somewhat similar to the well-known dry friction model, a force is created by the tire, which is proportional to the normal force and initially varies linearly with the slip angle. So the rst obser- vation here is that to generate side force as in cornering the tire must be subject to a certain level of side slip.
When this slip angle is too large [e. Some commercial tires generate less side force under such side-sliding conditions, but race car tire manufacturers desire to maintain most of the side force under moderate sliding conditions.
So beyond the linear slip range a commercial tire may have a negative slope whereas the racing tire should maintain a at shape, as shown. In most forms of racing it is desirable to create the fastest vehicle in a particular category. Traditionally, the effects of external aerodynamics are summarized in terms of drag, lift, and stability.
Usually the side force due to aerodynamic side slip was not examined carefully because race cars go much faster than the prevailing winds, and, instead of lift, the generation of efcient downforce became the main issue.
The three aerodynamic moments came to light when designers realized that vehicle stability and handling can be improved by properly balancing the downforce e. Such desirable aerodynamic downforce can be generated by adding lifting surfaces onto, or by modifying, the vehicles body.
When a vehicle moves fast, lateral instability may become uncomfortable from the drivers point of view. This was observed early with speed record cars that used huge stabilizers similar to airplane vertical surfaces in the back with pure aerodynamic stabilization in mind.
An example of this school of thought can be found in vehicles such as the Blue Flame rocket-propelled car that passed The common design aspect of these two cars is the effort to improve lateral stability by pure aerodynamic means e.
As noted earlier, only toward the end of the s did race car designers realize the huge advantage of using aerodynamics to augment tire traction and subsequently cornering and stability. To explain this statement we must return to Figure 1.
Let us assume for the sake of discussion that the vertical load on a tire resulting from the vehicle weight is kilograms kg.
Based on this gure the maximum cornering force that can be created by this tire is somewhat less than kg. Of course, good racing tires can generate larger forces and also the weight transfer due to vehicle dynamics is ignored here for simplicity.
The above condition can represent a vehicle in a steady cornering maneuver, and tire slip is represented by point A in the gure and tire full sliding is still a few degrees away. However, with aerodynamic downforce the normal force on the tire can be increased, whereas the vehicle weight is unchanged, resulting in improved performance e. If the driver decides to turn at the same speed same side force then the tire will require less slip point B and tire wear and heating will be reduced.
On the other hand, the driver can go much faster e. This simple fact was not realized until the mids, and by properly utilizing the aero-assisted tire performance, dramatic improvement can be obtained in cor- nering, in accelerating out of corners, in braking at high speed only , and in lateral stability.
The handling aspect was particularly important because by controlling the downforce distribution between the front and rear wheels, the vehicle stability could be altered e.The study also includes optimization of wing orientations direct angle of attack and geometry modifications on outer surfaces of the car are performed to enhance down force and lessen drag for maximum stability and control during operation.
The study also includes optimization of wing orientations direct angle of attack and geometry modifications on outer surfaces of the car are performed to enhance down force and lessen drag for maximum stability and control during operation.
In most forms of racing it is desirable to create the fastest vehicle in a particular category. Based on this gure the maximum cornering force that can be created by this tire is somewhat less than kg.
Race Car Aerodynamics : Designing for Speed by Joseph Katz (1996, Paperback)
Thickness of endplate is 32mm. Only four years later, in 1929, the Opel-designed rocket race car was the rst to employ wings see vehicle description in Hucho 1998, p. The motion of air around a moving vehicle affects all of its components in one form or another.