Identification of wake vortices in a simplified car model during significant aerodynamic drag increase under crosswind conditions

Wake vortices associated with a significant aerodynamic drag increase in a simplified notchback car model at a certain yaw angle and flow resulting in these vortices are identified in this study. In comparison with previous studies that only indicated the characteristic flow attachment on the leeward rear-end corner of the target car model under a significant drag increase, this study clarified the changes in the wake vortices in the target car model. Computational fluid dynamics simulations at typical yaw angles before and after the drag increase were performed. Two vortex visualization methods that depict the isosurface of the dimensionless vorticity and the vortex core lines of low-pressure vortices with swirling motions were applied. As results, four vortices were identified near the region where the surface pressure of the base decreases. These vortices were formed near the leeward side and center of the base and became stronger as the drag increased significantly. Therefore, these vortices are considered to contribute to the drag increase, in addition to enhancing the Coanda effect of the attached flow along the leeward rear-end corner. The flows associated with the four vortices were also identified by visualizing the streamlines passing through their vortex core lines. These findings will be useful in the suppression of significant aerodynamic drag increase at specific yaw angles.

Automated summary

This study identifies wake vortices associated with a significant aerodynamic drag increase in a simplified notchback car model. It clarifies the changes in the wake vortices and identifies four vortices near the region where the surface pressure of the base decreases. These vortices contribute to the drag increase and will be useful in the suppression of significant aerodynamic drag increase at specific yaw angles.