We present a FEM–BEM coupling strategy for time-harmonic acoustic scattering in media with variable sound speed. The coupling is realized with the aid of a mortar variable that is an impedance trace on the coupling boundary. The resulting sesquilinear form is shown to satisfy a Gårding inequality. Quasi-optimal convergence is shown for sufficiently fine meshes. Numerical examples confirm the theoretical convergence results.

中文翻译：

---

FEM-BEM灰浆联轴器在三个维度上解决了亥姆霍兹问题

我们提出了一种FEM-BEM耦合策略，用于在声速可变的介质中进行时谐声散射。借助砂浆变量实现耦合，该变量是耦合边界上的阻抗迹线。结果表明，半线性形式满足戈丁不等式。对于足够细的网格，显示了最佳收敛。数值算例验证了理论收敛结果。