Force analysis of underwater object with supercavitation evolution

Abstract

Supercavitation generally occurs as a result of flow acceleration along underwater body surface and is numerically investigated in this study using a compressible Navier-Stokes equations solver. Here, the supercavitating flow is assumed to be the homogeneous mixture of pure liquid water and vapour which are in kinematic and thermodynamic equilibrium. Liquid phase and cavitation are modeled by Tait equation of state (EOS) and isentropic one-fluid formulation, respectively. Convective terms of the governing equations are numerically integrated using Godunov-type, cell-centered finite volume MUSCL scheme on unstructured triangular mesh, whereas time integration is handled with the second-order accurate Runge-Kutta approach. Our interest is focused on the force analysis of traveling object with the formation, growth, evolution and even collapse of supercavity enveloping the object. It is found that skin friction drag exerted on the object can be reduced significantly by the formation of supercavity where viscosity of vapour is much smaller than that of liquid water. It is also observed that form drag acting on the object is influenced by the supercavitation. Collapse of supercavity over the body due to external perturbation not only damages underwater object but also alters form drag on it.