An oscillatory vorticity generator device for controlling the flow on an aero- or hydrodynamic surface of an element, the oscillatory vorticity generator device comprising: two main walls, positioned opposite to each other, forming a first pair of walls and two other walls, the four walls each having proximal and distal ends, the distal ends connected to an aero- or hydrodynamic surface; a connection connecting the walls at their proximal ends; and an opening in the aero- or hydrodynamic surface, the opening being substantially contiguous with the two main walls and the two other walls.