Abstract The problems of Acoustic-Structural Interaction (ASI) are commonly encountered in the simulation of the thin-walled structures immersed in the fluid. This interaction can affect the acoustic properties of the fluid and the dynamic characteristics of the structure. In this paper, a Non-Uniform Rational B-Splines (NURBS)-based Isogeometric Finite Element (FE) - Boundary Element (BE) symmetric coupling method is developed to study the ASI problems and the free vibration of the elastic structures submerged in the fluid. The geometry of the thin-walled structures is exactly modelled and discretized by utilizing the Isogeometric Reissner-Mindlin shell elements. This shell theory simplifies the continuity enforcement between NURBS patch boundaries. The Isogeometric Boundary Element Method (IGABEM) is applied to describe the acoustic field. In order to impose coupling constraints, a transformation equation of unknown variables on the interface between sound field and structure field is established, that is, sound pressure versus external force and particle velocity versus displacement. Different from the non-symmetric matrix obtained by the traditional direct BEM, a new variational formulation is introduced to obtain the symmetric coupling coefficient matrix, which maks this coupling approach suitable for a broad class of solvers and improves the robustness of the computation. The reliability and stability of the symmetric coupling method are verified by numerical examples considering acoustic and structural loadings. It is concluded that the symmetric coupling method possesses high accuracy, and can circumvent the limitation of traditional coupling method in solving open boundary problems.

中文翻译：

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用于声-结构相互作用的等几何对称 FE-BE 耦合方法

摘要 声-结构相互作用（ASI）问题是浸入流体中的薄壁结构的模拟中经常遇到的问题。这种相互作用会影响流体的声学特性和结构的动态特性。在本文中，开发了一种基于非均匀有理 B 样条 (NURBS) 的等几何有限元 (FE) - 边界元 (BE) 对称耦合方法来研究 ASI 问题和浸入水中的弹性结构的自由振动。体液。利用等几何 Reissner-Mindlin 壳单元对薄壁结构的几何形状进行精确建模和离散化。这种壳理论简化了 NURBS 补丁边界之间的连续性实施。等几何边界元法 (IGABEM) 用于描述声场。为了施加耦合约束，建立了声场与结构场界面上未知变量的变换方程，即声压对外力和质点速度对位移。与传统直接边界元法获得的非对称矩阵不同，引入了一种新的变分公式来获得对称耦合系数矩阵，这使得这种耦合方法适用于广泛的求解器并提高了计算的鲁棒性。通过考虑声学和结构载荷的数值算例验证了对称耦合方法的可靠性和稳定性。结论是对称耦合方法具有较高的精度，