Effect on drag of the flow orientation at the base separation of a simplified blunt road vehicle. Abstract The separated flow past the square-back model used in the experiments of Ahmed et al. [1] is controlled using flaps at the end of the top and bottom faces. A parametric study of the flow regarding the slant angle of the flaps is performed from pressure and force measurements as well as particle image velocimetry (PIV). When the bottom flap orientation is fixed, variations of the top slant angle evidence a drag versus lift quadratic dependence. This relationship presents self similarities changing the bottom flap angle.It is then observed that the lift is an affine function of both slant angles and the force a second order polynomial containing a coupling term between the two angles. These drag evolutions varying both angles are discussed and interpreted as contributions of the wake size, a drag induced by the lift and a local drag induced by the inclination of the flaps.