Optimizing Jets for Active Control of Wake Refinement for Ground Vehicles

The present study investigates active drag reduction of an Ahmed body with a rear slant angle of 25 deg. The drag is reduced by implementing slot jets on the rear slant and rear surface of the Ahmed body. Transient numerical experiments were conducted using the improved delayed detached eddy simulation (IDDES) turbulence model. Jet velocity, position, size, and angle were parametrically varied, and time-averaged drag coefficients for various jet configurations were calculated. Reynolds numbers based on the length of the Ahmed body were varied, but special focus was given to the high-drag case when Re = 1.4 × 106. It was found that by using slot jets at the rear and rear slant, the drag coefficient was reduced by 22%. In order to investigate the physical mechanisms for the reduction in drag, proper orthogonal decomposition (POD) was used to visualize the turbulent coherent structures in the near wake of the Ahmed body.