Active control of the wake behind the cylinder

Active control of the flow around a circular cylinder using a synthetic jet (SJ) array was experimentally investigated in a small wind tunnel. The prevailing method was flow visualization. Modification of the wake was investigated at two values of a dimensionless momentum coefficient (C-mu = 0.21 and 1.02). Various alpha and C-f parameters were tested (where alpha is the angle between SJs and the main flow direction and C-f is the frequency ratio). It was found that the control moves a separation point more downstream, i.e. the width of the wake can be reduced. Moreover, increasing frequency ratio C-f causes refining of the vortex structure. When the SJs are placed at the front or rear stagnation points, the wake tends towards the symmetrical pattern.