Numerical Simulation and Control of the Flow Around One or Two Ahmed Bodies

The aim of this work is to show that the drag coefficient of a bluff body is mainly linked to the circulation and the distance of the vortices in the close wake of the body. Thus an active control can be used to push away the vortices to decrease the pressure forces at the back. For the size of the vortices a passive control by means of porous layers is used taking benefit of the Kelvin-Helmholtz instability to change the vortex shedding. For two bodies with a short distance between them, the presence of strong vortices in the wake of the first body changes significantly the pressure force in front that governs the drag of the second body. The results of the control processes are illustrated on a single Ahmed body and on two Ahmed bodies following each other on top of a road.