Application of pressure-sensitive paint in supersonic nozzle research

An experimental study was conducted to evaluate the pressure-sensitive paint (PSP) technique as a means of obtaining global surface pressure distribution on the inside surface of a supersonic nozzle at NASA Langley Research Center. In this experiment, the PSP technique was used to measure the surface pressure distribution for several configurations of a convergent-divergent nozzle, which was also instrumented with a densely packed array of pressure taps. The PSP and pressure tap data were obtained simultaneously for each configuration of the nozzle, at several nozzle pressure ratios, to determine the effects of supersonic cavity-ramp vortex generators on the nozzle flow and performance. Results from the PSP data agreed very well with the pressure tap data and indicated that a pair of counter-rotating vortices were shed from the cavity vortex generator. The presence of these streamwise vortices caused a delay in the formation of the shock wave inside the nozzle.