Some innovative concepts for car drag reduction: A parametric analysis of aerodynamic forces on a simplified body

The aerodynamic torsor of a vehicle is among the most crucial parameters in new car development. This torsor has been decreased over the years by more than 33%, but beyond that further improvement has become difficult and challenging for car manufacturers. In this context, the present paper focuses on a parametric analysis of the trends in the aerodynamic forces. We report here aerodynamic force measurements carried out on a simplified vehicle model. Tests were performed in wind tunnel S4 of Saint-Cyr l’Ecole for different airflow configurations in order to isolate the parameters that affect the aerodynamic torsor and to confirm others previously suspected. The simplified model has flat and flexible air inlets and several types of air outlet, and includes in its body a real cooling system and a simplified engine block that can move in the longitudinal and lateral directions. The results of this research, which can be applied to any new car design, show configurations in which the overall drag coefficient can be decreased by 2%, the aerodynamic cooling drag coefficient by more than 50% and the lift coefficient by 5%. Finally, new designs for aerodynamic drag reduction, based on the combined effects of the different parameters investigated, are proposed.

Figure optionsDownload as PowerPoint slideHighlights
► Air outlet in the exhaust tunnel is the optimal solution for torsor reduction.
► Drag is smaller when the underside outlet is centered over the model width.
► Drag is independent of the position of the air outlet in the wheel arch.
► Drag and pitch moment coefficients increase with inlet/outlet section ratio up to 0.7.