Investigation of an explicitly modeled solid ocean floor on a shallow water UNDEX event

Abstract

Current practices for modeling the ocean floor in underwater explosion simulations call for application of an inviscid fluid with soil properties. A method for modeling the ocean floor as a Lagrangian solid, vice an Eulerian fluid, was developed in order to determine its effects on underwater explosions in shallow water using the DYSMAS solver. The Lagrangian solid bottom model utilized transmitting boundary segments, exterior nodal forces acting as constraints, and the application of prestress to minimize any distortions into the fluid domain. Elastic materials were used, though multiple constitutive soil models can be applied to improve the accuracy. This method is unable to account for soil cratering effects, however it provides the distinct advantage of modeling contoured ocean floors such as dredged channels and sloped bottoms absent in Eulerian formulations. The dynamic loading effects of the investigated bottom contours were found to be negligible in the analyzed cases as a result of the bulk cavitation zone which dominates the chosen fluid field and serves as a buffer to the target. In addition to its utility in bottom modeling, implementation of the non-reflecting boundary along with realistic material models can be used to drastically reduce the size of current fluid domains.http://archive.org/details/investigationofn109455530Approved for public release; distribution is unlimited