Control of separation shock unsteadiness in an incident-shock-induced interaction

Separation shock unsteadiness in an incident-shock-induced interaction with and without control is evaluated in a Mach 2.05 flow using a 14(circle)shock generator. An array of mechanical vortex generators (MVGs) in the form of rectangular vanes (MVG1), ramp vanes (MVG2), and a delta ramp (MVG3) is placed 14 delta upstream of the interaction region ( delta= 5.2mm being the local boundary layer thickness at the interaction). Among all the devices tested, MVG1 shows a maximum reduction of the separation length (about 28% relative to the no-control case). The spectra at separation also show a shift in the dominant frequency from 220Hz without control to 539Hz withMVG1. Interestingly, the peak rms (root mean square) value is seen to occur with control at much larger intermittency values (gamma(sigma), (max) = 0.92 for MVG1) in contrast to the no-control case in which it occurs gamma(sigma), (max) = 0.5 as reported so far. The auto-correlation at the separation and reattachment shock locations indicates the presence of relatively small-scale structures with control as compared to the case without control. Out of all the control cases tested, MVG1 exhibits better separation control with a relatively lower unsteadiness level.