Numerical prediction of tip vortex cavitation noise of underwater propellers using RANS solver, bubble dynamics and acoustic analogy

摘要

In this study, tip vortex cavitation noise of underwater propeller is predicted using a one-way coupled method consisting of RANS solvers, bubble dynamics model, and the acoustic analogy. First, the hydrodynamic flow field around the underwater propeller is predicted by using the RANS solver. The tip-vortex structure is reconstructed by applying the vortex model in association with the flow field obtained from the RANS solver because the tip vortex suffers from being dissipated by the numerical damping intrinsic to the numerical scheme. Before the vortex model is applied, the vortex core location is identified using the minimum λ_2 criterion. The magnitude of the modeled vortex is determined by using the circulation of the local flow field around the identified vortex core near the tip of the propeller blades. Then, the bubble dynamics model is employed to predict tip-vortex cavitation. The initial nuclei distribution is adjusted to represent the quality of water used in the corresponding experiment. The Keller-Herring and the bubble trajectory equations are solved to predict the volume and the location of each nucleus in the hydrodynamic flow field, respectively. Finally, cavitation noise is predicted by considering each nucleus as a point monopole source. The propeller, named HSP17, is newly designed and manufactured to provide benchmarking data, especially for the effects of the skew angles on the tip-vortex cavitation. The proposed numerical method is applied to predict the tip-vortex cavitation inception and noise of the HSP17. The entire body of submarine is also included to account for the effects of the boundary layer flow of the body upstream on the tip-vortex cavitating flow of the HSP17 downstream. The validity of the present numerical approach is confirmed by comparing the numerical results with the experimental ones.