Abstract: The coupled finite element method(coupled FEM) and coupled finite element method/boundary element method(coupled FEM/BEM) are always adopted to solve the structural-acoustic problems. and it is known that the finite element methods behave “over-stiffness” which induce the large numerical error for the structural-acoustic problems. In order to soften the “over-stiffness” and improve the results of FEM, a coupled ES-FEM model is extended to solve the structural-acoustic problems consisting of a plate structure interacting with the fluid medium. Three-node triangular elements and four-node tetrahedral elements are used to discretize the two-dimensional(2D) plate and three-dimensional(3D) fluid, respectively, as they can be generated easily and even automatically for complicated geometries. Numerical studies have verified that the gradient smoothing technique can provide a proper softening effect to the model, and hence significantly improve the accuracy of the solution for the coupled systems, which will lay the foundation for further applications.

Key words: edge-based smoothed finite element method (ES-FEM);structural-acoustic;vibration and Noise