Surface Discharges for High-Speed Boundary Layer Control

Abstract

Surface plasma discharges have been shown to be effective in altering laminar boundary layers. Judicious choice of electrode shape can create a discharge that emulates a or a bump. The virtual wedge discharge has been shown to create a local pressure rise with potential applications to vehicle control. The virtual creates a lesser pressure rise, but strong distortion of the boundary layer. In the current work the effect of the bump discharge on laminar shock boundary layer interactions is explored. Laminar shock boundary layer interactions are created with an impinging shock on a flat plate at a freestream Mach number of 5. The primary instrumentation is a low-modulus elastomer doped with a pressure-sensitive dye. Intensity distributions from the dye are imaged to interrogate the surface pressure. Displacement of surface markers provides surface shear information. Results show the presence of Gortler vortices in the reattaching shear flow. The Gortler vortices are also evident in temperature-sensitive paint images. These vortices are evident in the intensity images from the elastomer, which can be related to the surface pressure, but are not readily evident in the surface shear measurements. The DC discharge moves the separation line upstream, but does not change the wavelength of the Gortler vortices.