Impact of orifice orientation on a finite span synthetic jet interaction with a crossflow
The formation and evolution of flow structures associated with a finite span synthetic jet issued into a zero pressure gradient boundary layer were investigated experimentally using stereoscopic particle image velocimetry. A synthetic jet with an aspect ratio of AR 18 was mounted on a flat plate and its interaction with a free stream, having a velocity of U 10 m/s (Red 2000) at momentum coefficients of Cm 0.08, 0.33, and 0.75, was studied. The effect of the orifice pitch (a 20 90) and skew (b 0 90) angles on vortex formation as well as the global impact of the synthetic jet on the flow field was explored in detail. It was found that the orifice orientation had a significant impact on the steady and unsteady flow structures. Different orifice skew and pitch angles could result in several types of vortical structures downstream, including: no coherent vortex structure, a single (positive or negative) strong vortex, or a symmetric vortex pair. In all cases, the velocity near the wall was increased; however, cases with higher blockage (i.e. more wall normal, transverse orifice) resulted in a strong velocity deficit in the free stream where orifices with lower pitch angles yielded in an increase in velocity throughout. The analysis is concluded with a summary of quantitative metrics that allude to flow control effectiveness.