International audienceA prior analysis of the effect of steady cross wind on full size cars or models must be conducted when dealing with transient cross wind gusts effects on automobiles. The experimental and numerical tests presented in this paper are performed on the Willy square-back test model. This model is realistic compared to a van-type vehicle; its plane under-body surface is parallel to the ground and separations are limited to the base for moderated yaw angles. Experiments were carried out in the semi-open test section at the Conservatoire National des Arts et Métiers (CNAM) and computations were performed at the Ecole Centrale de Nantes (ECN). The ISIS-CFD flow solver, developed by the CFD Department of the Fluid Mechanics Laboratory of ECN, used the incompressible unsteady Reynolds-Averaged Navier-Stokes equations. In this paper, the results of experiments obtained at a Reynolds number of 0.9 106 are compared with numerical data at the same Reynolds number for steady flows. In both the experiments and numerical results, the yaw angle varies from 0° to 30°. The comparison between experimental and numerical results obtained for aerodynamic forces, wall pressures and total pressure maps shows that the unsteady ISIS-CFD solver correctly reflects the physics of steady three-dimensional separated flows around bluff bodies. This encouraging result allows us to move to a second step dealing with the analysis of unsteady separated flows around the Willy model
