非定常空化流致噪声的数值模拟

The loading noise of unsteady cavitating flow around a hydrofoil is calculated by combining CFD and acoustic boundary element method, meanwhile, the corresponding cavitation noise is predicted by bubble volume pulse method in spherical cavitation bubble theory. The results indicate that non-cavitation loading noise is mainly subject to a linear spectrum at low frequency. Moreover, the acoustic fundamental frequency is basically the same as the vortex shedding frequency, and the spectrum peaks are at its low-order harmonics. However, when cavitation occurs, the continuous spectrum is significantly enhanced compared with the linear composition, and the overall acoustic pressure level of loa-ding noise is increased compared with that of non-cavitation. In addition, the bubble noise becomes the main noise source with a broad spectrum. The first and second peak frequencies of the acoustic power spectrum density are consistent with the cloud cavitation and the trailing vortex shedding frequencies, respectively. Nevertheless, the acoustic power density of bubble noise is concentrated in the higher frequency bands, which may be resulted from the growth and shedding behavior of multi-scale bubbles behind the tail of cavity.