CFD Simulation of the Impact of Variable Diffuser Geometry on the Stability of a Light Vehicle

Reducing fuel consumption and Greenhouse gases GHG emissions involves improving the aerodynamic coefficients of means of transport. At the same time, guaranteeing the stability of a vehicle travelling at high speed seems to be a key priority for researchers. Reducing lift is essential to increase the downforce exerted on a car. The diffuser plays a serious role in aerodynamic efficiency and greatly improves stability and grip at high speeds. This study delves into the examination of how alterations in diffuser geometry impact the reduction of lift and subsequently drag. Initially, a prototype car model was meticulously crafted utilizing CATIA software, later imported into ANSYS Fluent for comprehensive numerical Computational Fluid Dynamics (CFD) analysis, crucial in evaluating its aerodynamic performance. Employing the Reynolds-Averaged Navier–Stokes method based on the k-ε turbulence model for system closure and a complex unstructured mesh design, the Navier-Stokes equations were solved. The resulting streamline distributions and pressure fields distinctly illustrate the efficacy of integrating a dual diffuser featuring three vanes set at a 15° inclination angle. This modification notably enhances the vehicle’s stability, concurrently reducing the lift coefficient CL by 32.6% and the drag coefficient CD by 3.4% when juxtaposed with the base vehicle lacking a diffuser.