Control of a three-dimensional blunt body wake using low and high frequency pulsed jets

We present experimental evidence of pressure changes in the wake of a three-dimensional blunt body by the use of periodic pulsed jets. The jets are pulsed tangentially to the shear layers separated from the trailing-edges of a classical square-back Ahmed body. The Reynolds number based on the model's height is ReH = 3.105. Significant decrease (respectively increase) of the rear pressure are achieved considering low and high frequency pulsing. Low frequency actuation (St = Hf/Uo = 0.4, where f is the frequency and Uo the upstream velocity) is shown to enhance the global wake mode and to increase drag. On the contrary, dynamical effects associated to the particular flow control strategy provides a significant drag decrease for the higher frequency forcing (St = 11.5). Time-averaged pressure on the back surface of the model and velocity measurements on the wake illustrates the main effects of such actuation and introduce new strategies for drag control of three-dimensional geometries.