High-Speed Schlieren and Pressure-Sensitive Paint Visualization of an Impinging Jet

This study experimentally investigated the transition from asymmetric to axisymmetric unsteadiness in a supersonic impinging jet using high-frequency surface pressure measurements, schlieren, and pressure-sensitive paint (PSP). The experiment utilized a flat-lip, conical nozzle (5 mm exit diameter, Mach 2 design) and an impingement plate positioned six exit diameters away. The Nozzle Pressure Ratio (NPR) was varied between 3.7 and 4.3. While the jet primarily operated in an asymmetric mode across this NPR range, an axisymmetric resonance was identified near NPR 4.1 which generated the strongest pressure fluctuations on the impingement plate. The transition between these two modes of jet unsteadiness was analyzed using the three measurement techniques.