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A two-seat sports car was designed with the initial marketing goal of breaking the Laguna-Seca racetrack record. This study reports the external aerodynamic modifications that resulted in a significant increase in the vehicle's downforce. The main objective of this study is to report about the method used, which was significantly simpler and much faster than traditional methods used by the automotive industry. Because of the simplicity of the tools used (e.g., computations and wind tunnel), valid engineering conclusions could have been reached only by combining these tools.

The aerodynamic characteristics of a sprint car model were tested in a small-scale wind tunnel. Lateral characteristics such as the side force and rolling moment were measured in addition to the vehicle's downforce and drag. Measured data indicated that during the rapid cornering of these race cars, lateral loads are as important as downforce. Since literature search revealed no aerodynamic data on such asymmetric vehicles, a typical baseline sprint car model was tested first with particular focus on large sideslip conditions. Modified wing and side fin geometries were also tested for improved visibility and in search for additional downforce. The experimental data indicate, for example, that a reduced endplate size of the main wing can improve driver visibility without significant loss of aerodynamic downforce.

Aerodynamic lift and drag coefficients of various open-wheel racing car configurations were experimentally investigated. These configurations included several basic fuselage shapes which, in view of the current regulations, did not make use of the “ground effect” to provide negative lift. To these fuselage shapes, which had some positive lift, both unswept wings and delta wings were added to increase their negative lift. The experiments were made with one-tenth scale models, but in order to evaluate these results, comparison is made with full-scale wind tunnel experiments. The results of this work show that useful conclusions can be drawn, based on the small-scale tests, about the relative effectiveness of these aerodynamic devices. Furthermore, with the aid of these lifting surfaces an overall lift coefficient of about minus one was found to be obtainable.

The aerodynamics of a generic, enclosed-wheel racing-car shape without wheels was investigated numerically and was compared with one-quarter scale wind-tunnel data. Because both methods lack perfection in simulating actual road conditions, a complementary application of these methods was studied. The computations served for correcting the high-blockage wind-tunnel results and provided detailed pressure data which improved the physical understanding of the flow field. The experimental data was used here mainly to provide information on the location of flow-separation lines and on the aerodynamic loads; these in turn were used to validate and to calibrate the computations. This combined computational/experimental approach, with the computations being used primarily to study attached now conditions, can reduce wind-tunnel experimental program length and allow for additional testing of more complex problems such as flow separation.

The design of passenger vehicles for improved aerodynamic characteristics will result in reduced fuel consumption and better road handling during high-speed driving. In this research, techniques were developed to measure the aerodynamic drag and lift forces acting on a full-scale vehicle under road conditions and then were compared with results obtained on reduced-scale models in a wind tunnel. A number of configurations which characterize common vehicle forms were investigated for their effect on aerodynamic efficiency and fuel consumption, Experimental speeds were between 70 and 110 km/h, these being representative of highway driving conditions. A typical passenger vehicle of the three-box type was selected for the experiments, and its exterior form was altered by means of attaching various configurations to its front, rear, and underbody portions.

A three-dimensional computer simulation technique was combined with wind-tunnel testing during the aerodynamic development of an enclosed-wheel prototype race car. This approach proved that valuable time can be saved by investigating some of the important design parameters before a vehicle is built. One of the major advantages of a computational approach is that it contains information such as pressure or velocity distribution on and near the whole vehicle. This abundance of data is essential for understanding major design trends and sensitivities, and can steer the design toward fruitful modifications. Once the vehicle's body plan is finalized, the method can be used to further modify local details and to design and position a complicated rear wing cluster. At this phase of wing design, the availability of the pressure distribution on the entire wing surfaces is vital to a successful design.

During a high-speed drag race a race-car nose may accidentally be lifted by the aerodynamic loads causing the dangerous ‘Blow Over’ phenomenon. Such aerodynamic loads were investigated for a wide range of pitch angles in small-scale wind-tunnel tests, using a Top-Fuel Dragster model. A simple device, creating negative vortex lift, was proposed and tested in an effort to reduce the pitch up moments during the initial phases of the ‘Blow Over’. Results of the wind tunnel tests indicate that when deploying the proposed device, immediately after the front wheel liftoff, alleviation of the ‘Blow Over’ is possible.

A generic, Indy-type, open-wheel, racecar model was tested in a low speed, fixed ground wind tunnel. The elevated ground plane method was selected for the road simulation since one of the objectives was to allow flow visualization under the car (and this is not possible with current rolling ground wind tunnel setups). Consequently, both the groundplane and the wind tunnel floor were transparent to facilitate the flow visualization under the vehicle. The aerodynamic loads were measured by a six-component balance, and an effort was made to quantify the partial contributions of the various vehicle components. The main trends and aerodynamic interactions measured with this setup appear to be similar to data measured in larger wind tunnels using rolling ground simulations. As expected, the two wings and the underbody vortex generators generated most of the aerodynamic downforce.

The aerodynamic drag and lift of a sport-motorcycle was investigated in a full-scale and in a 1/6th scale wind tunnel tests. The results show the large vertical load transfer to the rear wheel as vehicle’s speed increases. Consequently, several simple dive and splitter-plates were tested to balance the motorcycle and primarily increase the front axle aerodynamic downforce. These devices were added at a relatively low position on the bodywork in order to avoid adverse handling effects while leaning in turns. This study shows the level of downforce that can be generated by simple add-ons without major alterations to the bodywork. Consequently, for higher levels of aerodynamic downforce, larger underbody surfaces or wings are needed.

The flow field over a vehicle and the resulting integral quantities, such as downforce and drag are a direct outcome of the vehicle's shape. During the initial developmental stage, therefore, it would be beneficial to have an inverse capability, dictating vehicle shape, based on a prescribed set of desirable aerodynamic parameters. Although such methods exist for airfoil design, their extension to complex vehicle geometries is far more complicated. Consequently, an alternate approach is experimented with here, whereby a desirable trend in the surface pressure distribution is specified. Using an iterative method, the vehicle shape is modified until the ‘target’ trend in the pressure distribution is met. In the present study such a systematic approach was proposed and used to develop an enclosed wheel racecar shape. During this process of refining the vehicles geometry, computational fluid dynamic tools were used.