Improved Effectiveness of Vane-Type Vortex Generators for Incident Shock-Induced Separation

Abstract

An experimental investigation is conducted to improve the control effectiveness of an array of vane-type vortex generators (VG) implemented 6 δ upstream of an incident shock-induced separation generated using a 14-deg wedge in a Mach 2.05 flow. Initially, the effect of an array of rectangular vanes (RRV) is studied by varying the vane 1) chord to height (c/h)=7.2, 4.2, 2) angle α=24, 20, 18, and 16 deg, 3) height to boundary-layer thickness (h/δ)=0.75, 0.5, 0.3, and 0.2, and 4) interdevice spacing to height (s/h)=12, 9.5, 7.5, 6.5, 5.7, 5.5, and 5.0. Similar tests were also performed for ramp vanes (RV) with α=24 deg. Due to inherent design differences, an RRV device generates a larger region of vortex influence relative to an RV device. Therefore, reducing s/h significantly reduces the extent of uncontrolled separation regions between neighboring VGs that improves their separation control capability. The best performing RRV devices with vane height h/δ=0.5, h/δ=0.3, and h/δ=0.2 show maximum reduction in separation extent of nearly 80, 74, and 70%, respectively, relative to no control. The equivalent RV devices, however, show much reduced control effectiveness. All controls exhibit a shift in the dominant separation frequency to higher values, indicating a reduction in the overall extent of separation.