A numerical study of unsteady cavitation on a hydrofoil

Abstract

The unsteady turbulent cavitation on a hydrofoil with finite span and NACA-0015 section is studied numerically. For the computations, a two-phase flow approach based on homogeneous mixture approximation is adopted in which liquid-vapor mixture is modeled as an inter-penetrating continuum with the phase compositions represented by volume- fraction and the inter-phase mass transfer computed using a finite-rate model derived from bubble dynamics. An implicit, finite-volume based projection algorithm was developed that couples velocity, phase compositions, and pressure. Turbulence is modeled using Reynolds-averaged Navier-Stokes (RANS), large eddy simulation, and RANS/LES hybrid approaches. A suite of multiphase computational fluid dynamics (MCFD) solvers was built using OpenFOAM, an object-oriented, open-source CFD tool-kit, being validated for steady and unsteady cavitating flows on hydrofoils and marine propulsors. The large eddy simulation (LES) and the RANS/LES hybrid results on the hydrofoil closely reproduced the salient features of the unsteady sheet/cloud cavitation such as the breakup of sheet cavity by re-entrant jet, and the formation and collapse of cloud cavity. The lift and drag force predictions in a range of cavitation number were also found to be in good agreement with the experimental data in terms of the mean values, the root-meansquare values, and the spectral contents.