Abstract:
In this paper, the large eddy simulation (LES) of a supersonic jet impinging on a large plate was presented. The nozzle-to-plate space was 2.08 times of nozzle exit diameter, and the nozzle-pressure ratio was equal to 4.03. Results indicated that the location and intensity of shock waves were periodical. As the Mach disc oscillates in the axial direction, the underexpanded gas had more sufficient space for expansion and thus can reach a higher speed. In the wall jet zone, the large-scale annular vortical structure was continuous. Along the radial direction, the large-scale vortices broke up and generated smaller vortices. Sound wave propagation to the upstream from the wall was observed. After reflection from the lip of the nozzle, it propagated to the downstream near the shear layer, and a feedback loop was formed. It dominated the monotone generatione. Fast Fourier transform was applied to the pressure fluctuation. The results verify that the feedback loop had the same frequency as the tone. Proper orthogonal decomposition was employed to analyze the velocity fluctuation. The modes and their energy contribution rates were calculated. The jet boundary, Mach disc and the oblique shock wave, the recirculation area and the wall jet all had strong correlation. The generation and evolution of large scale turbulence structures in turbulent field were presented and analyzed.