Affiliations: Aeronautical and Maritime Research Laboratory, Defence
Science and Technology Organisation, Melbourne, Victoria, Australia | Department of Civil Engineering, Monash University,
Clayton, Victoria, Australia
Note: [] Aeronautical and Maritime Research Laboratory, Defence Science
and Technology Organisation, GPO Box 4331, Melbourne, Victoria 3001, Australia.
Tel.: +61 3 9626 8754; Fax: +61 3 9626 8999; E-mail:
lloyd.hammond@dsto.defence.gov.au
Abstract: The LS-DYNA/USA (Underwater Shock Analysis) coupled finite element
codes are being investigated as a tool for predicting the local response of
compliant plate structures subjected to far-field underwater explosion. It had previously been observed in LS-DYNA/USA models that
extraneous pressure build-ups emanating from the DAA (doubly asymptotic
approximation) boundaries may occur in the surrounding fluid region of the
model, which inevitably lead to erroneous modelling of fluid-structure
interaction and inaccurate structural responses. These instabilities typically
result in divergence of the solution and eventually premature termination of
the simulation. After a comprehensive investigation, it was found that the
instabilities did not arise if the finite element model was hydrostatically
initialised before conducting the LS-DYNA/USA simulation. The purpose of this study is to investigate the need for achieving
hydrostatic equilibrium prior to the modelling of the shock wave propagation
through the fluid-structure media. The method for achieving static equilibrium
with the current version of the LS-DYNA/USA software is presented. The example
simulations presented show that the hydrostatic initialisation procedure is
effective in removing instabilities occurring at the DAA-fluid boundary,
associated with the USA ambient hydrostatic pressure condition.
