A COUPLED FEM BEM FOR FLUID-STRUCTURE INTERACTION USING RITZ VECTORS AND EIGENVECTORS

In this paper, the finite element (FEM) and the boundary element metho d (BEM) are combined together to solve a class of fluid-structure inte raction problems. The FEM is used to model the elastic structure and t he BEM is used to model the acoustic fluid. Quadratic isoparametric el ements are used in both the FEM and BEM models. Continuity conditions of pressure and normal velocity are enforced at the fluid-structure in terface on which the normal vector is not required to be uniquely defi ned. An enhanced CHIEF formulation is adopted to overcome the nonuniqu eness difficulty at critical frequencies. To reduce the dimension of t he coupled structural acoustic equations, the structural displacement is approximated by a linear combination of either Ritz vectors or eige nvectors. An error norm and a participation factor are defined so that it is possible to evaluate the accuracy of a solution and to omit vec tors with small participation factors. Example problems are solved to examine the accuracy of the numerical solutions and to compare the eff iciency of the Ritz vector and eigenvector syntheses.