Numerical Simulation of Cavitating and Non-cavitating Flows over a Hydrofoil

Abstract

The compressible hydrodynamic approach previously developed for small Mach number non-cavitating flows has been extended to simulate cavitating flows as well as non~cavitatingflows. The extension is made possible by assuming a complex equation of state relating density and pressure to cover the liquid phase and the gas phase. Thus, the cavitation phenomenon is regarded as a single-phase flow phenomenon enabling the elimination of the cavity closure condition. The numerical model is an unsteady 3~ dimensional flow model based on a large eddy simulation approach. It is applied to typical thin hydrofoils and thick hydrofoils at non~cavitating conditions and various cavitating flow conditions, including moving cavity, stable sheet cavity and sheet cavity/cloud cavity cyclical flow conditions. Computations are carried out primarily for 2-dimensional foils, but 3-dimensional flow characteristics are also examined. The computational results are compared with some available data; good quantitative and qualitative agreements are indicated. It is considered very significant that the sheet cavitation/cloud cavitation phenomenon is found to be similar to the viscous boundary layer flow separation/vortex shedding and washout phenomenon in many respects. Cavitation is found to trigger boundary layer separation in otherwise non- separated flow.