<p>The presence of wall-pressure fluctuations in turbulent cavitating flows can lead to substantial changes in noise, structural vibrations and material erosion. These pressure fluctuations are difficult to model in numerical simulations, and their source has not been well understood due to limitations in measurement techniques. Previous research on cavitation pressure field mainly focus on the leading-edge region and closure region of cavity, while assuming uniform saturated vapor pressure within the cavity. However, the existence of unsteady flow structures which has been verified in both experimental observations and numerical modeling, i.e., re-entrant jet and shock wave, shows the nonuniform and unsteady flow features within cavity. It is worth noting that pressure is the critical parameter to determine the phase change rate for cavity evolution. Consequently, it is necessary to conduct systematic studies of the pressure fluctuation characteristics and illustrate their effects in cavity dynamics. In the current study, flow visualization and wall-pressure measurement in high frequency on the order of MHz were employed using a synchronizing sampling technique to quantify the wall-pressure fluctuation characteristics and their source in transient cavitating flows. Results are presented for cloud cavitating flows under re-entrant jet dominated shedding and shock wave dominated shedding, respectively. Compared with re-entrant jet, the interactions between shock wave and cavity could induce pressure peaks with high magnitude within cavity, which will collapse the local vapor along its propagating path and reduce local void fraction. Furthermore, statistics analysis shows that within the cavity, wall-pressure fluctuations increase with the distance to cavity leading edge increase in the first half of cavity length, and the skewness and kurtosis decrease, indicating the asymmetry and intermittency of wall-pressure fluctuation signals decrease. In shock wave dominated cavity shedding condition, the skewness and kurtosis increase. These results can provide data to improve the accuracy of turbulence modeling in numerical simulation of turbulent cavitating flow.</p>

Wall-Pressure Fluctuations Inside Attached Cavitation

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

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