Influence of orifice orientation on a synthetic jet-boundary-layer interaction

The mean streamwise velocity field downstream of a synthetic jet embedded in a turbulent boundary layer (Re-theta = 830) was investigated experimentally. Of particular interest was the change in the mean flowfield resulting from changes in the yaw orientation of the rectangular synthetic jet orifice. Three yaw angles (beta = 0, 10, 20 deg) were considered. Time-averaged and phase-averaged hot-wire measurements were obtained at two positions downstream of the synthetic jet actuator. The measurements show that when the orifice is aligned with the mean freestream velocity (beta = 0 deg), a flow structure consistent with a weak counter-rotating vortex pair was observed in the boundary layer. For beta = 10 deg, the mean streamwise velocity contours suggest the presence of a single vortex in the boundary layer, whereas for 0 = 20 deg, the flow structure resembles a horseshoe vortex formed as a result of flow blockage by the jet.