Nonlinear Dynamic Analysis of Fluid‐Structure Systems

Abstract

A numerical procedure for computing the dynamic response of coupled fluid‐structure systems is developed and used to evaluate the effects of nonlinear behavior of the structure and fluid. The procedure includes cavitation of the fluid, which is modeled as a bilinear compressible material, in addition to nonlinear models of the structure. A mixed displacement‐pressure formulation for the fluid is used, in which the pressure is approximated independently of the fluid displacements, allowing satisfaction of the bilinear equation of state in the weak sense and not requiring reduced integration for the tangent stiffness matrices. A standard displacement finite‐element formulation is used for the structure. The symmetric coupled equations of motion are in terms of nodal displacements and are solved by a fully implicit time integration method. Response results from analysis of a simple fluid‐structure system show that cavitation and nonlinear structural behavior can interact to affect the response of the coupled system. However, cavitation appears to have a small effect on the earthquake response of concrete gravity dams.