The Experimental Analysis of Cavitating Structure Fluctuations and Pressure Pulsations in the Cavitation Station

摘要

The experimental analysis of unsteady cavitating flow has been performed to compare the static pressure dynamics and cavitation cloud structure dynamics. The analysis of the unsteady cavitation flow field was performed in the wake of bluff body in the laboratory cavitation station. The pressure oscillations were measured downstream of the bluff body with a recessed installation of the pressure sensor. The cavitation cloud structure dynamics was visualized using high speed camera. Pressure and image acquisition was performed simultaneously. The results of both measurements were analyzed in low frequency and high frequency intervals. The low frequency analysis of both pressure and cloud structure oscillations was performed in the interval from 0 to 1000 Hz. The high frequency analysis of the pressure fluctuations was performed with band pass filtering from 300 to 400 kHz and amplitude demodulation. Comparison of the static pressure and cavitation cloud structures fluctuations caused by cavitation cloud shedding in the wake of bluff body showed similarity between both signals. Two distinct frequencies of flow oscillations were recognized and the influence of cavitation number on the strength of pressure and cloud structure oscillations was quantified. The amplitude demodulation method was used to show and discuss the connection between the low and high frequency pressure oscillations.