Search Results

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.

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.

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.

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.

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.

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.