Calculation Of Tip Vortex And Tip Vortex Cavitation Flows Around Three-dimensional Hydrofoil And Propeller

Cavitation flow is a kind of very complex vapor-liquid two phase flow phenomena, It contains turbulent, transformation, compressible and unsteady characteristics. Cavitation is a hotspot issues in a number of industrial areas like: ship, aerospace and bio-medicine. In the shipping industry, the low pressure in tip vortex core will cause the liquid phase occurre fracture, thus lead to the formation of tip vortex cavitation. Tip vortex cavitation is not only the main vibration and noise sources of ship, but also the arch-criminal of denudation on the rudder after propeller. To control or eliminate these adverse effects of tip vortex cavitation in the design process, it is necessary to accurately understand the mechanism and physical characteristics of tip vortex and tip vortex cavitation. Therefore, the research on tip vortex and tip vortex cavitation on three dimensional airfoil and propeller is very necessary.In this paper, based on the OpenFOAM platform, firstly we simulated the unsteady cloud cavitation on two-dimensional airfoil, by comparing with the experimental results, we verified the numerical method used in this paper. And than analyzed the formation process and development of sheet cavitation, and observed the step by step breaking phenomenon on sheet cavitation.In the research of the tip vortex, we firstly simulated the tip vortex flow around a three-dimensional hydrofoil. The research results show that in the framework of RANS, nonlinear k-ε turbulence model which based on the nonlinear eddy viscosity assumption compared to the standard k-ε turbulence model which based on Boussinesq linear eddy viscosity assumption can better predict the multi-eddy structure and its development and fusion process, and can reduce the turbulent viscous dissipation at the tip vortex. On this basis, this paper simulated the more complex propeller vortex flow, the research results show that nonlinear turbulence simulation can predict the spiral structure of propeller vortex, while the linear simulation is almost failed to predict the spiral structure. Linear turbulence simulation also failed to predict the process of tip vortex rollover to the suction surface of propeller, also the predict development of tip vortex process lags far behind the nonlinear turbulence simulation results.Finally, the tip vortex cavitation flow of propeller are simulated. Found by contrast, the prediction of tip vortex cavitation by nonlinear turbulence simulation can be better, although the linear turbulence simulation can predict the attached cavitation on the suction surface it failed to predict the tip vortex cavitation. And by comparing with the full wet flow, we found that dure to the existence of tip vortex cavitation, the tip vortex structure becomes much more complicated, and the intensity of tip vortex was significantly lower than that full wet flow. that is, to a certain extent the tip vortex cavitation inhibit the development of the tip vortex. By analysis the stress and strain distribution on the tip vortex zone, and the turbulence production, we also found that the linear turbulence simulation failed to predict the nonlinear relationship between stress and strain, and over prediction the tip vortex turbulence dissipation rate.