Numerical investigation of cavitating tip vortex dynamics and how they influence the acoustic characteristics

Abstract

The surface waves traveling on tip vortex cavities are one of the main contributors to underwater radiated noise (URN). However, these waves cannot be easily predicted, especially the mode associated with the cavity volume variations, which hinders research into the hydroacoustic mechanism. This paper presents a method for extracting the surface waves from numerical predictions, which successfully captured all the theoretical dispersion relations of these surface waves. This method was then used to analyze the tip vortex cavitation (TVC) dynamics and how they influence the URN with an acoustic analogy. Low- and medium-frequency URN are shown to be mainly emitted by the surface waves related to the cavity volume variations. The significant tones at the dominant frequency and the broadband hump center frequency are further studied with the main noise sources found to be the cavity radial fluctuations and the TVC resonance.