Abstract
Keywords: wheel, wheelhouse, rim, Ahmed body, CFD
According to the international findings of experiments, the addition of wheelhouses and rotating wheels to an aerodynamically optimized car body results in an increase in drag- and lift coefficients by 30% and 40%, respectively. Some of the publications report the dominance of the effect of rear wheels over that of the front wheels in drag increase for the case of both model and full scale cars. In the past years extensive investigations were carried out by using CFD tools to determine an appropriate model of the flow field inside wheelhouses of cars. In this paper the flow field is computed by means of RANS modeling.
The paper summarizes the results of the investigation on the effect of wheelhouses and wheels mounted on a given configuration of the well known Ahmed-body. The Ahmed-body was chosen because a number of results from both experimental and numerical investigations on this body without wheels are available in the literature. This gave the basis for validation of the CFD results.
Most of the investigations, including also the present ones were mostly carried out by using simplified wheels without detailed tread and rim. As the geometry and the opening of wheel rims plays essential role regarding to the cooling of brake discs authors investigated the effect of open wheel rims on the topology of the flow field within the wheelhouse as well, as their effect on the force acting on the simplified vehicle model. For the investigation of the effect of the wheel rim openings the generic vehicle body (Ahmed-body) was used. Three different configurations were then investigated where the difference was the amount of opening of the rim. Besides the investigation of the flow field topology the change of forces acting on different surfaces of the vehicle model are analyzed by means of integration of static pressure and shear stress distributions.
In this study ANSYS-Fluent 6.3 software was used for detailed flow field analysis, validated against measurements published in the corresponding literature. Conclusions concerning the mechanism of change in flow field topology and that of the forces acting on various parts of the vehicle are drawn.