Influence of Gap Flow on the Cavitating Response of a Rectangular Hydrofoil

Abstract

A commercial URANS solver is used to analyze the cavitating flow field around a rectangular, cantilevered hydrofoil with a small gap between the free end and the wall of a cavitation tunnel. A transport-equation based cavitation model is used along with an artificial compressibility correction for the turbulent eddy viscosity. The objective is to improve the understanding of the unsteady interactions between the 3-D gap flow, sheet-cloud cavitation, gap cavitation, tip vortices, and their dependence on the cavitation index. It is found that the numerically-predicted wetted pressure distributions, cavitation patterns, and load coefficients agree well with experimental measurements and observations. The results suggest that the presence of cavitation significantly modifies the boundary layer flow near the tip and the tunnel wall, disrupts the formation of the tip-leakage vortex, and enhances other secondary flows. Although the numerical model was able to simulate the general dynamics of sheet and gap cavitation, a more refined mesh and higher fidelity turbulence models (e.g. DES or LES) are needed to resolve the fine vortex structures in the tip, tip vortex cavitation, and the highly transient features of 3-D cloud cavitation.