On the influence of eddy viscosity in the numerical modelling of air cavities

Abstract

This article aims to link the physical modelling of air cavities to their numerical modelling with a RaNS solver. The largest challenge in predicting the cavity characteristics numerically lies in correctly modelling their closure region. According to Reboud et al. [1], the commonly over-predicted eddy-viscosity at the water-gas interface reduces the development of the re-entrant jet and can thus prevent the occurrence of shedding. Computations were carried out using two different eddy-viscosity correction functions: a power function as described by Reboud et al. [1] and Coutier-Delgosha et al. [2] and a Gaussian function proposed by Rotte et al. [3]. The Gaussian correction function does not contain large gradients when the local density approaches pure gas or liquid. It also has no bias towards one of the fluids and is expected to improve the stability of the simulation and the physical modelling of the problem.