Wake Analysis and Drag Reduction for a Square Back Ahmed Body Using LES Computations

The trend of automotive design induces vertical shape in the region of the rear tailgate, which leads to important aerodynamic losses in the rear back of vehicles. Experimental wake analysis performed behind a square back bluff body shows influence of the vortex transport in the mixing layers backward the detachment region. It is therefore important to carry on studies on turbulent wake understanding in order to find solutions for drag reduction with the current vehicle design. This paper presents LES simulation results computed in order to describe transport of large vortices produced in the 3D wake structure behind a square back bluff body. Prior to this result analysis, we will show comparison with experimental results, helpful to validate these transient computations, performed with different pulsed jets implemented at the top end of the square back, close to the separation zone. Analysis of these computations results will also focus on the relation between amplitude of the flow structure and Cd results.