Numerical Modeling of Underwater Explosion with Fluid-Structure Interaction

Abstract

A numerical model for three-fluid flow including air, water and high explosive (HE) material is extended to fluid-structure interaction (FSI) problems. The aim is to study the complex interactions between compressible multi-phase flows and deformable structures in near field underwater explosions (UNDEX). In this model, the ideal equation of state is used for air. The stiffened gas equation of state is used for water, and the Jones-Wilkins-Lee (JWL) equation of state is used for HE materials to describe the detonation process. An arbitrary Lagrangian Eulerian (ALE) method is then formulated for the five-equation model for the fluids and combined with Lagrangian numerical methods for the structural domain. For the fluid domain, the spatial discretization is performed with a second order finite volume scheme. A tangent of hyperbola for interface capturing (THINC) technique is applied to sharpen the transitioning phase. The temporal discretization is based on explicit Runge-Kutta (RK) method. The Lagrangian numerical method is based on a large-deformation formulation with fully integrated, hourglass-free finite elements and explicit timestepping. The coupling is performed by ‘glueing’ the structure to the surface of the fluid domain. Automatic remeshing is included for possibly large deformations of the structure. Several examples demonstrate the capabilities developed.