LES Investigation of the noise characteristics of sheet and tip leakage vortex cavitating flow

Abstract

In the present paper, cavitation noise induced by sheet cavity and tip leakage vortex cavity (TLVC) together generated by a NACA0009 hydrofoil are numerically investigated with Ffowcs Williams-Hawkings (FW-H) equations. Large eddy simulation (LES) combined with Schnerr-Sauer cavitation model is utilized and a satisfactory result is obtained as compared with the referenced experimental measurements. It is found that even though the volume of TLV cavity is much smaller than that of sheet cavity, their acoustic levels are comparable to each other. A close relationship is indicated between cavity evolutions and their radiated noises, which vary periodically for both sheet and TLV cavities. Moreover, intense sound pulses of pseudo-thickness and pseudo-loading noise are observed especially during the collapse process. It is indicated that the rise in far field pressure and action of the dilatation term inside the cavities may trigger the collapse of both kinds of cavities in the flow, resulting in sound impulses. It is worth mentioning that in agreement with previous investigations, high pressure distribution and jets at the ends of sub-TLVCs are noted to have a close relationship with the collapse of sub-TLVCs. Noise generated by sheet cavity is higher than that generated by TLV cavity at the dominant Strouhal number of 0.74, with relatively high values of both pseudo-thickness and pseudo-loading noises at the dominant Strouhal number. While noise of TLV cavitating flow has acoustic energy concentrated at either low Strouhal numbers or high Strouhal numbers for the two terms, respectively.