Indy cars and F-1 race cars are complex machines. In order to optimize the car performance, engineers and constructors commit large amounts of time and money to R&D. Aerodynamic efficiency is the goal of each team in developing a competitive car for the next racing season. Testing techniques vary from wind tunnels, to on-track data, and even computational methods, such as Computational Fluid Dynamics (CFD). Originally employed in aerospace design techniques, CFD applications are now used in structural analysis, automoblile design and other non-aerospace fields. In Indy car and F-1 racing, teams can spend up to 100 days (per year) testing in wind tunnels and have full time aerodynamicists analyzing new chassis designs. Each team seeks an aerodynamic advantage which will result in a competitive edge.
In 1993 the Rahal/Hogan Indy car team began building a new chassis. Team designers included a CFD application in component design. The project was headed by MIT researcher and lecturer David P. Keenan. "CFD", says Keenan "has matured to the point where we can use it in the conceptual design phase for exploratory work. It should cut out a lot of model building early on, allowing us to get through a lot of concepts more quickly than was previously possible." Keenan used an airfoil shape that allowed the Indy car design team to specify the pressure distribution over its surface. "What we do is build a computational model of the full vehicle, run CFD calculations, and use powerful visualization tools that come with the software (Rampant, from Fluent Inc. Lebanon N.H.) to explore the complete flow domain". Keenan and the design team look for such things as high and low pressure regions and vortices, measurements that cannot be duplicated in wind tunnels. According to Keenan, the use of CFD in Indy car racing, "is a two-pronged effort. We are not only exploring CFD to understand the flow over the car, but also developing tools that will be advantageous to race engineers. We can tell them what the flow will do, but they have to figure out how to make the Indy car take advantage of it."
Throughout the motorsports world of today, and in particular the Indy Car (CART) series, the seasons are becoming longer. No sooner has one season ended that another is beginning. Test teams and engine developers are employed year round to meet the challenge of the upcoming season. To remain competitive, a team must undergo continous development, even if there are strict rules on modification. As a result, there is a demand for advanced design and analysis techniques which are practical, cost-effective and above all, accurate. Computer simulation will continue to to be used as a design and development tool in order to:
- Reduce time scales (elapsed time from computer model to component design).
- Increase performance.
- Enhance engineering knowledge.
Design modifications in the future will be based on the overall aerodynamic package of the car. Driver safety is always a major concern when regulations are changed in the CART series. One area of concern is the drivers helmet. The drivers helmet is exposed to airflow in excess of 200mph. Severe buffeting can not only effect the aerodynamics of the car, but can jeaopardize the driver's safety in the event of a frontal impact. Helmets are now being designed with aerodynamic aids mounted on the back of the helmet. According to Simpson Race Products (safety helmet designer), the aerodynamic aid performs three separate functions:
- It prevents the helmet from lifting at high speeds.
- It stops the buffeting effect (on the drivers head and neck).
- It helps clean up the airflow from the helmet going back to the car's rear wing.
The stability of the current Indy Car racing regulations has led to similar chassis designs. There is very little difference in the physical appearance of the various team cars. The difference in car performance is the result of fine aerodynamic design and car setup, particularly on speedway circuits. The size and shape of the front and rear wings (speedway setup) are areas that will see changes in future designs. A race car that is set up to allow the driver to lap the Indianapolis Speedway wide-open can have too much downforce. Downforce comes with the penalty of unwanted drag. The optimum car setup is to run a minimum downforce so the car is faster down the straights, while still running wide-open in the turns. One way to achieve this is to reduce the size of the front and rear wings. The anhedral front wing and reduced rear wing was one solution seen in the 1994 Indianapolis 500. One team owner takes it a step further. Jim Hall suggests, "I think you could run at Indianapolis with no wing at all." The necessary downforce being created by the venturi tunnels in the uderbody of the car. Drag reduction is the major concern in future chassis designs. Hall asserts, "I think you have the major part of the car near the front and it would be teardrop-shaped. Less drag. I think the wheels still have to stick out, don't they? I think you have a lot of work to see if it's worth trying something radically different from what they're running today. But I think you could do it. I mean, today you've got a simulation program so that you could see how it would work without actually doing it. Or you could make a model and bring it to a wind tunnel. In a few hours you could have a big laugh and say, 'No we're going to go back like we thought we should'." Or maybe it would bring about a whole new chassis design that would be:
- Adapatable to different engines.
- Adapatable to the different race ciruits.
- Aerodynamically efficient.
Information provided by: http://www.nas.nasa.gov