Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 07, 2019 - November 08, 2019
An underexpanded jet impinging on a flat plate is numerically studied in this study. The jet, which is exhausted from a circular nozzle with the nozzle pressure ratio higher than the critical pressure ratio, becomes underexpanded and impinges on the flat plate perpendicularly. Axisymmetric Euler equations are solved using the TVD scheme and the flow field at different nozzle pressure ratios and nozzle-plate distances is simulated to investigate the behavior of shock waves in the jet. At comparatively low pressure ratio, the incident shock wave generated near the nozzle rim intercepts the jet and reaches the jet axis. However, a Mach disk forms across the jet axis at higher pressure ratio and the incident shock does not reach the jet axis but interacts with the Mach disk. A plate shock appears in front of the flat plate, and its location depends on the nozzle-plate distance and the pressure ratio. As a result, it was found that when the plate shock wave is near the node of barrel-shaped cell, the jet oscillates periodically and strongly, and when the Mach disk forms in the jet at high pressure ratio, the periodicity of the oscillation disappears. Furthermore, it was found that the periodicity of the oscillation appears again when the third cell begins to form at larger nozzle-plate distance, even when the Mach disk forms.
