NUMERICAL SIMULATION OF PROPELLER TIP VORTEX CAVITATION INCEPTION CONSIDERING THE EFFECT OF NUCLEI GROWTH AND COLLAPSE

Tip vortex cavitation (TVC) is the earliest type of cavitation that occurs on propellers, and it significantly enhances the underwater radiated noise level of ships once it happens. Therefore, TVC inception prediction is vital for cavitation inception speed determination and has attracted much attention from experts and scholars in the ship field. The explosive growth of microscopic nuclei under the action of low pressure of vortex core is an important mechanism for tip vortex cavitation inception, while the conventional macroscopic cavitation models in Eulerian framework use empirical parameters to model the influence of microscopic nuclei and cannot accurately simulate this process, which affects the accurate prediction of propeller cavitation inception. To overcome the limitations of traditional simulation methods, this paper develops and applies an Eulerian-Lagrange cavitation inception numerical method based on bubble dynamics and water phase compressibility to simulate TVC inception. Comparison with experimental results shows that this model can accurately predict propeller TVC inception. This paper not only investigates the effects of different incoming nuclei sizes on cavitation inception from a microbubble perspective, but also studies the significant influences of tip vortex flow characteristics on nuclei evolution, and thus reveals the sound generation mechanism of cavitation inception in propeller tip vortex flow field. Under optical criterion for cavitation inception, larger-sized gas nuclei are more likely to be captured by tip vortices and grow explosively. Nuclei gradually approach the vortex core low-pressure region under tip vortex suction. Nuclei grow explosively under continuous low-pressure action at the vortex core, and rapidly contract and collapse rapidly after reaching maximum size, producing strong acoustic pressure pulse.