An effective approach for topological design to the acoustic–structure interaction systems with infinite acoustic domain

This research contributes to the topology optimization of acoustic–structure interaction problems with infinite acoustic domain by focusing on two issues, namely, the variation of the acoustic–structure interface and free-floating elements. To handle the variation of the coupling interface, we divide the analyzed domain into the bounded and unbounded domains by using a virtual surface. For the bounded domain where the coupling interface may appear, we model it with the mixed displacement–pressure (u/p) finite element method (mixed FEM). Then, the boundary element method (BEM) is utilized to model the non-reflecting boundary conditions on the truncated surface. The mixed FEM enables the explicit representation of the acoustic–solid interface in the optimized domain to be circumvented. By spatial variation of the mass density, shear and bulk moduli in the mixed FEM, the topology optimization procedure can be easily implemented similar to standard density approaches. With regard to the free–floating elements, we establish a connected component filter to delete these useless elements. This treatment avoids unreasonable but possibly optimized results. The proposed method is verified by several optimization examples.