Numerical Analysis of the Flow Over Convertibles

In the present study, the exterior air flow over convertibles together with the interior flow in the passenger compartment has been calculated using the commercial CFD program STAR-CD. The investigations have been performed for a SLK-class Mercedes with two occupants. The computational mesh consists of about 3 million hexahedra cells.

The detailed informations of the calculated flow field have been used to elaborate the characteristic flow phenomena and increase the physical understanding of the flow. The influence of different geometrical modifications (variations of roof spoiler, variations of the draft stop behind the seats etc.) on the flow field and the air draft experienced by the occupants has been analyzed.

To proof the accuracy of the numerical results, wind tunnel experiments in a full scale and 1:5 scale wind tunnel have been carried out for the basic car model as well as for several geometrical variations. Detailed comparisons of the measuring and computational results showed an acceptable agreement of absolute velocity values as well as trends of the geometrical variations.