Control of Fin Shock Induced Flow Separation Using Vortex Generators

This work demonstrates the control of the shock-induced separated flow generated by a sharp fin placed on a cylindrical surface (fin-on-cylinder shock-wave/boundary-layer interaction) with an incident Mach 2.5 flow. Well-quantified distortions in the form of streamwise vortices are embedded into the boundary layer using single subboundary-layer vortex generators (VGs). At four device heights downstream from the VG trailing edge, the boundary layer exhibits a peak deficit in the streamwise velocity from the undistorted boundary layer of 60%. At 15 device heights, the boundary layer was energized to a peak surplus of 25% in the streamwise velocity. These two VG streamwise placements (four and 15 device heights) were employed to emphasize the impact of direct vortex interactions and boundary-layer energization on separation vortex control. It was found that having an energized boundary-layer incident on the fin-on-cylinder SBLI made very little change to the separation vortex size and the associated pressure distribution. However, placing the vortex generator much closer significantly mitigated the separation vortex size, and several azimuthal placement locations showed an elimination of the separation vortex. Cross-sectional velocity and vorticity fields showed a strong reduction in spanwise velocity and streamwise vorticity above the separation vortex in the successful configurations.