MIXED VARIABLE DIRECT COUPLING FEM-BEM APPROACH TO STRUCTURAL-ACOUSTIC COUPLING PROBLEMS

摘要

Prediction of structurally coupled interior acoustic fields subjected to harmonic excitation in the low to mid frequency range using integrated boundary element and finite element methods is presented. Direct boundary element method (BEM) is used to model the acoustic field while either conventional finite element method (H-FEM) or hierarchical finite element method (PFEM) is used to model the elastic structure. Coupled equations of acoustic field and elastic structure are assembled into a complete set of system of equations to obtain the response of the structural-acoustic interacting system. Several case studies selected from existing literature are considered to investigate certain aspects of coupling between structural and acoustical systems. As the first case study, a linear duct problem is emphasized and accuracy of the boundary element results at low frequencies is analyzed by using higher order quadrature integrations. The second case study involves a cavity-backed plate and sound transmission problem is investigated. Mixed variable direct coupling H/P-FEM-BEM approach is applied in the analysis. Cavity surface is discretized with flat rectangular boundary elements. Flexible part of the cavity is discretized either by conforming 36-degree-of-freedom rectangular plate elements in H-FEM modeling or by a single trigonometric hierarchical rectangular plate finite element in P-FEM modeling. Responses in frequency domain are evaluated from accuracy standpoint through comparisons to those obtained in previous studies and to existing analytical results.