VOLUMETRIC 3-COMPONENT VELOCIMETRY MEASUREMENTS OF THE FLOW FIELD ON THE REAR WINDOW OF A GENERIC CAR MODEL by

Volumetric 3-component velocimetry measurements are carried out in the flow field around the rear window of a generic car model, the so-called Ahmed body. This particular flow field is known to be highly unsteady, 3-D and characterized by strong vortices. The volumetric velocity measurements from the present expe-riments provide the most comprehensive data for this flow field to date. The present study focuses on the wake flow modifications which result from using a simple flow control device, such as the one recently employed by Fourrié et al. The mean data clearly show the structure of this complex flow and confirm the drag reduction mechanism suggested by Fourrié et al. The results show that strengthening the separated flow leads to weakening the longitudinal vortices and vice versa. The present paper shows that the volumetric 3-component velo-cimetry technique is a powerful tool used for a better understanding of a 3-D un-steady complex flow such as developing around a bluff-body