Exciting a cavitating tip vortex with synthetic inflow turbulence: A CFD analysis of vortex kinematics, dynamics and sound generation

Abstract

Cavitating tip vortices are one of the main contributors to underwater radiated noise (URN). To predict URN and evaluate propeller designs, it is necessary to predict cavity dynamics. To this end, a tip vortex generated by an elliptical wing is simulated in wetted and cavitating conditions, using scale-resolving simulations. The vortex is excited by synthetic inflow turbulence with varying inflow turbulence intensities. Vortex kinematics and cavity dynamics are analysed, and validated against experiments and a semi-analytical model from literature. The far-field radiated noise is analysed using an acoustic analogy. Using a background noise correction, the sound due to inflow turbulence is removed, and the sound due to cavity dynamics is isolated. Based on the sound spectra, the main noise generating mechanisms are identified. Cavitating simulations predict an increase in far-field radiated noise of approximately 15 dB, while doubling the inflow turbulence intensity results in an increase of approximately 10 dB.