PERFORMANCE CHARACTERIZATION OF A HIGHLY OFFSET DIFFUSER WITH VORTEX GENERATOR JETS

The effect of blowing vortex generator jets on the performance of a hi ghly offset (S-duct) diffuser was investigated experimentally (M(1) = 0.6, Re-eq = 3.46 x 10(7)). Inlet plane total pressure and Mach number contours were mapped using a pitot probe. Exit plane total pressure r ecovery, static pressure recovery, and Mach number contours were mappe d with blowing on and off, using pitot and static probes. Cross-wire a nemometry was used to measure the mean velocity and turbulence intensi ty in three dimensions at three spanwise locations on the exit plane w ith the blowing on and off. Without blowing, the flow on the lower sur face of the diffuser was massively separated. Blowing at 0.50% mass fl ow ratio through three lower-surface vortex generator jets reduced the size of the separated-dow region and the exit plane boundary-layer th ickness, increased pressure recovery, and decreased turbulence intensi ty. Blowing re distributed momentum within the diffuser and altered th e secondary flow structure. However, the exit plane total and static p ressure fields were more distorted with blowing than without.