Influence of Rear-end Shape on Transient Aerodynamic Characteristics Caused by Time Variation of the Relative Wind Direction

Abstract

In the present study, unsteady vehicle aerodynamics caused not by a periodic condition but by an intermittent disturbance has been investigated, especially focusing on the aerodynamic drag. Aerodynamics of simplified vehicle models, which had different geometry only in the rear-end corner, were measured in a wind tunnel with a transition of aerodynamic yaw angle. From the measurement results, relationship between unsteady aerodynamics and aerodynamic phenomena has been investigated. A model with the rounded corner shape showed hysteresis on the aerodynamic force. Transitional phenomenon of flow separation on the rear-end corner was considered as a cause of the hysteresis.