Simulation of Active Drag Reduction for a Square-Back Vehicle

An active flow control approach was investigated in order to reduce the aerodynamic drag of a generic square-back vehicle. Using Large Eddy Simulations, it could be shown that steady blowing along the rear edges of the vehicle can reduce the drag by more than 10%. The blowing angle was varied, and a most effective angle of 45 degrees was found. The control method leads to a delay of shear layer vortex generation and to changes in the wake structure that cause a pressure increase on the rear surface of the vehicle. A simple estimation of the energy balance showed that the energy input needed for the active control is relatively large. Only for one case investigated in this study a small net power gain was found.