Aerodynamic drag control by pulsed jets on simplified car geometry

Aerodynamic drag control by pulsed jets is tested in a wind tunnel around a simplified car geometry named Ahmed body with a rear slant angle of 35°. Pulsed jet actuators are located 5 × 10⁻³ m from the top of the rear window. These actuators are produced by a pressure difference ranging from 1.5 to 6.5 × 10⁵ Pa. Their excitation frequency can vary between 10 and 550 Hz. The analysis of the control effects is based on wall visualizations, aerodynamic drag coefficient measurements, and the velocity fields obtained by 2D PIV measurements. The maximum drag reduction is 20 % and is obtained for the excitation frequency F _j  = 500 Hz and for the pressure difference ∆P = 1.5 × 10⁵ Pa. This result is linked with a substantial reduction in the transverse development of the longitudinal vortex structures coming from the left and right lateral sides of the rear window, with a displacement of the vortex centers downstream and with a decrease in the transverse rotational absolute values of these structures.