Mid-wake wing tip vortex dynamics with active flow control

Abstract

The development of a wing tip vortex under the effect of synthetic jet (SJ) actuation was examined for a rectangular, square-tipped wing having a NACA 0012 airfoil using hotwire anemometry at a chord Reynolds number Rec=8×104. Three control configurations were considered for a comparative study, namely case C1 with momentum coefficient Cμ=0.004 and an actuation frequency F+=0.96, case C2 with Cμ=0.04 and F+=0.96 and case C3 with Cμ=0.04 and F+=0.29. Under case C3, the vortex was stretched into an ellipsoid shape with a nearly 60% decrease in the peak circumferential velocity and the core axial vorticity. The vortex core radius largely broadened suggesting that the lower frequency control configuration allowed the synthetic jet to travel larger distances into the vortex bringing turbulent structures within its core. This resulted in an increased mixing and subsequently a more diffuse vortex. Measurements of the vortex development in the near and mid-wake regions (up to x/c=5) showed that the circumferential velocity was largely reduced under the effect of the SJ actuation. The enhanced turbulent mixing at the inner region of the vortex resulted in an accelerated outward diffusion of its core even under non-optimal control configurations.