Downstream influence of turbulent flow past vortex generators

Abstract

Vortex generators (VGs) are typically positioned upstream of a boundary layer separation region. Their effectiveness depends on incoming flow conditions (Mach number, Reynolds number and boundary layer characteristics), geometrical configuration (vane or ramp, height, width, and angle of incidence) and spacing. Device-induced vortices and following decay allow VGs to be used as a passive control device. This study uses pressure-sensitive paint (PSP) to determine the global surface pressure pattern for a flat plate flow in the presence of VGs (counter-rotating vanes, co-rotating vanes and ramps). The freestream Mach number is 0.64 and 0.83. The ratio between the height of the VGs and the incoming boundary layer thickness is 0.2, 0.5 and 1.0. The standard deviation in the spanwise pressure in the streamwise direction is used to determine the downstream influence of turbulent flow past VGs. Increasing the height of VGs causes device-induced vortices to propagate farther downstream.