Numerical investigation of tip vortex cavitation inception and noise around NACA16-020 using bubble dynamics

Hybrid numerical methodology is developed for the efficient and accurate prediction of wing tip vortex cavitation and its noise. The proposed method consists of four sequential steps: prediction of flow field using CFD techniques, reconstruction of tip vortex using vortex models, simulation of tip vortex cavitation formation using bubble dynamics model, and prediction of flow noise due to vapour bubble using spherical monopole source model. The tip vortex cavitation formed in the water flow passing by the wing consisting of NACA16-020 is investigated. First, entire flow field is predicted by solving the RANS equations with finite volume based CFD techniques. However, it is well known that the numerical RANS solution has difficulty in predicting the tip vortex accurately due to its excessive numerical damping. The more resolved tip vortex is synthesized by using the vortex model of which parameters are computed using the RANS solutions. Then initial nuclei were distributed upstream and their development during their journey through the synthesized vortex flow field are simulated using the spherical bubble dynamics model. It is shown that the predicted tip vortex cavitation phenomena match the experimentally observed one. Finally, flow noise due to tip vortex cavitation is predicted by using the bubble noise model which is basically equivalent to monopole source. There are good agreements between the predicted and measured ones. These results highlight the applicability of the current numerical methodology to the prediction of CIS as well as cavitation noise of a wing-shaped body.