Fluid-structure Coupling Methodology For Undersea Weapons

Abstract

Accurate prediction of underwater explosion damage to naval targets is an important aspect of weapon design. The stiffness of water makes ths a difficult problem; target deformation modifies the pressure in the surrounding fluid, changing the pressure loading. Thus, it is necessary to couple the fluid and structure simulations. This is accomplished by running both simulations as separate processes that communicate after each fluid integration step. The fluid solution is carried out on a fixed, Cartesian product grid, which does not coincide with the body surface. Geometry routines included in the Euler module determine which cells are in the fluid, in the structure and intersected by the structure surface. A modified stair-step boundary treatment that accounts for local surface motion and orientation represents the body surface without introducing a complicated data structure or restricting step size. This approach can accommodate thick, singly wetted or thin, doubly wetted surfaces. The latter are common in underwater applications where naval vessels may have fluid backed surfaces. Computational examples are presented that include a moving piston, planar shock interaction with a cylinder as well as explosive loading of a double walled cylinder, an externally stiffened cylinder and a ship. The first two cases are two-dimensional and demonstrate the efficacy of the method, whle the latter are three-dimensional and provide proof of principle for the application of this method to complex naval structures. Transactions on the Built Environment vol 71, © 2004 WIT Press, www.witpress.com, ISSN 1743-3509