Aerodynamic Analysis of the Ride Height Dependency of a High-Performance Vehicle Equipped with a Multichannel Diffuser in Ground Effect

Racing and high-performance vehicles utilize their underbody floor and diffuser as efficient mechanisms to generate the majority of their downforce. Previous work has primarily been focused on simplified bluff bodies with plane diffusers. The little published work on more complex multichannel diffusers has shown improved downforce generation over plane diffuser, but with limited understanding of the flow features and their response to ride height. This study analyses the performance and complex flow features of a high-performance vehicle equipped with a multichannel diffuser at various ride heights. A comparative assessment between RANS and DDES simulations is performed, which shows that both models adequately predict downforce and underbody flow features at high to medium ride heights, but only the DDES model is able to capture the unsteady flow behavior, which dominates the diffuser at low ride heights. Subsequently, an in-depth aerodynamic analysis of the vehicle’s ride height dependency is conducted using the DDES simulations. The analysis shows the crucial role of the diffuser’s side plate vortices on the flow entertainment and formation of vortices at the separators. Moreover, the analysis describes the influence of ride height on the strength and stability of the vortex flow in the diffuser. Findings at very low ride heights demonstrate that strong interaction between the vortices and flow along the ground plane cause the formation of relatively unstable vortices, which provide less flow entertainment and thereby cause a reduction in downforce.