Turbulent Flow Measurements of the Under-Expanded Free Jet and Jet Impinging on a Flat Surface

摘要

In this summary, we obtained 2D2C P1V measurements of free jets and impinging jets with the nozzle pressure ratio NPR = 2.77 and nozzle-to-plate distance e = 10 mm. The mean axial velocity profiles obtained at this NPR showed the maximum velocity along the nozzle perimeter. Profiles of RMS fluctuating axial velocity v'_(rms) for NPR = 2.77 had an additional peak at X/D_j = 0. Results obtained from the PIV measurements of impinging jets have shown the jet flow deflection caused by the impinging surface. The jet shear layers were created from the nozzle outlet and traveled further downstream until they impinged on the solid surface. The turbulent kinetic energy contours illustrated significant high levels along the shear layers near the nozzle exit and on top of the solid surface, where the jet shear layers impinged. The presence of a stand-off shock and a stagnation region was observed in the color contours of velocity magnitude, and the peaks of turbulent kinetic energy was found in the region of stand-off shock. Further works will include flow measurements at various nozzle-to-plate distances and nozzle-pressure-ratios.