Numerical Simulation with a DES Approach

This paper presents a finite-volume-based detached-eddy simulation for the prediction of flow around a passenger vehicle. The flow solver used is ISIS-CFD developed by the CFD Department of the Fluid Mechanics Laboratory of Ecole Centrale de Nantes. The validation is carried out by a crosswind simulation around the squareback Willy model. The model was designed in order that separations are limited to the region of the base for a moderate yaw angle. This model without sharp corners on the fore body and a square base is more convenient for the analysis of unsteady separations limited on its leeward side and base. The angle between the upstream velocity and the direction of the model varies between 0° and 30°. The results are compared to a previous numerical study obtained with a RANS simulation and experimental data. All comparisons (aerodynamic forces, wall pressures, and topology of total pressure) show that DES simulations give a better agreement with experimental data, particularly for the large yaw angles. The second model is the classical Ahmed body with the slant angle of 25°. With a RANS simulation, we have a massive separation in the wake while with DES simulation, the agreement is better with the experimental data. This paper shows that DES simulations give an improvement of the wake prediction for the automotive flow.