Accurate Drag Prediction Using Transient Aerodynamics Simulations for a Heavy Truck in Yaw Flow

Abstract

Aerodynamic development of a full-scale truck presents a challenge for experimental testing due to the scale of the vehicle relative to most wind-tunnel test facilities. Numerical simulation is becoming more prevalent for assessing design changes and improving vehicle aerodynamic drag. In this process, the cumulative effects of small design changes are needed. Furthermore, the drag must be considered both at zero crosswind and with five degrees crosswind yaw angle in order to properly represent typical driving conditions. It is well-known that the aerodynamics of heavy trucks are complicated by a very transient wake flow that causes large fluctuations in base pressure, and therefore in the drag coefficient. This effect is often even more prevalent at non-zero yaw angles. The transient wake flow presents a challenge for effectively using simulation tools to predict the drag effects of small design changes, which may have some influence on the wake flow and base pressure.