Research On Cavitating Flow Using Openfoam

Cavitation is a kind of flow phenomenon which frequently happens in the working period of a variety of hydrodynamic turbo machines.The nature of cavitation is the phase change from water to vapor.In early times potential method and experimental methodology are widely used to investigate cavitating flow.With the development of computer science, more and more researchers have started to apply numerical method to the research of cavitating flow around various objects.In this thesis three aspects of research efforts have been accomplished using the open source OpenFOAM, which include the comparison of the effect on the predicting capacity about different turbulent models and cavitating models, the calculations of cavitating characteristics of2D hydrofoils and the unsteady simulation of cavitating flow around a3D.Twist11N hydrofoil.Three grids of different density are used to compare the influenc of grid on the simulation results, the velocity field, the distribution of turbulent viscosity, the wake and hydrodynamic forces on the foil are discussed, which reveal that the case with400grids on the foil is appropriate for the simulation. Adopting the fine grid, the effect of turbulent models and cavitating models on the results are investigated. From the analysis of forces on the hydrofoil and flow parameters we find standard k epsilon turbulent model and Schnerr cavitating model are more effective for the simulation of cavitation.Using the standard k-ε turbulent model and Schnerr cavitating model the steady flow around2D NACA0009hydrofoil and transient flow around2D NACA0015are studied. For the NACA0009case, the flow cavitating numbers are set to the variation between0.3and1.2. The lift and drag on the foil and the cavity shape above the suction side have been studied due to the variation of cavitating number. Under the conditons of angle of attack as8degree and cavitating number as0.8the cavitating flow around NACA0015is investigated in detail to reveal the periodic variation of velocity, pressure distribution and cavity shape. On the basis of Foeth’s experimental data, the numerical model of Twist11Nfoil is established to study the fully wetted flow and cavitating flow. Through the analysis of the cavitating flow around Twist11N foil, we find that the cavity length in streamwise and the width in spanwise decrease with the increment of cavitaing number.