The Effects of Cooling Air on the Flow Field around a Vehicle 2016-01-1603

Cooling air flow is an important factor when it comes to vehicle performance and operating safety. In addition, it is closely linked to vehicle aerodynamics. In recent years more and more effort is being spent to optimize the losses generated by the flow through the vehicle. Grille shutters, better sealing and ducting are only some examples for innovations in this field of work, resulting in a lower contribution of the cooling air flow to overall drag.

But cooling air not only affects the internal flow of the vehicle but also changes the flow around it. This paper will show changes in the flow field around the generic DrivAer model resulting from cooling air flow, especially in the wake behind the car and in the region around the front wheels. The results were gathered using PIV measurements, multi-hole-probe measurements and pitot tube measurements in the 1:4 model scale wind tunnel of IVK University of Stuttgart. Unless stated otherwise, all the measurements were conducted with rotating wheels and ground simulation. Additionally, CFD simulations were performed using the Lattice-Boltzmann solver Exa PowerFLOW. These simulations allow an even closer look at the flow field around the vehicle, especially in the under-floor region that is hardly accessible in measurement.