Time-Resolved Visualization of G\"{o}rtler Vortices in a Pulsed Convex Wall Jet using Fast Pressure-Sensitive Paint

The time-resolved formation and structure of G\"{o}rtler vortices in a pulsed convex wall jet are studied in this work. While the presence of G\"{o}rtler vortices in laminar boundary layers on concave surfaces can be clearly observed, their presence in wall jets flowing over convex surfaces is difficult to discern due to transition to turbulence in the outer part of the jet. This work employed fast-response pressure-sensitive paint (PSP), which has a documented flat frequency response greater than 5 kHz, to visualize the time-resolved formation of the wall jet and the details of the G\"{o}rtler vortices. The radius of curvature of the wall jet was 8 cm, and the Reynolds number (based on slot height and jet exit velocity) was varied between $5\times 10^{2}$ and $4\times 10^{4}$. The characteristic spanwise wavelength of the vortices was studied as a function of jet Reynolds number. Furthermore, as the Reynolds number was increased, various secondary instabilities were observed that led to laminar-turbulent transition.