The analysis of fluid-structure coupled waveforms and the attenuation of these waveforms in a flexible waveguide is carried out. The physical configuration contains an expansion chamber connected by an extended inlet/outlet by means of vertical lined flanges. The governing boundary value problem is solved by using Mode-Matching (MM) technique. The associated eigen expansions of field potentials include non-orthogonal eigenfunctions and the related eigen-sub-systems are classified in the non-Sturm Liouville category, whereby the use of generalized orthogonal characteristics has ensured the point-wise convergence of solution. The low frequency approximation (LFA) which relies on the limited propagating modes is developed and is compared with MM solution. In the low frequency regime, a good agreement between MM and LFA results is found. Furthermore, the numerical experiments are performed to analyze the effects of absorbent linings and edge conditions on the attenuation of flexural modes. The guiding structure is exited with the structure-borne mode incident as well as the fluid-borne mode incident. It is found that the use of edge conditions and the absorbent linings significantly affect the attenuation of structure-borne mode and fluid-borne mode, respectively.

中文翻译：

---

带有吸收衬里的法兰和不同边缘条件的弯曲模式的衰减分析。

对柔性波导中的流固耦合波形以及这些波形的衰减进行了分析。物理配置包含一个扩展室，该扩展室通过垂直的衬里法兰通过扩展的入口/出口连接。通过使用模式匹配（MM）技术解决了控制边值问题。场势的相关本征扩展包括非正交本征函数，并且相关的本征子系统被归类为非Sturm Liouville类，因此，使用广义正交特征可确保解的逐点收敛。开发了依赖有限传播模式的低频近似（LFA），并将其与MM解决方案进行了比较。在低频状态下，在MM和LFA结果之间找到了很好的一致性。此外，进行了数值实验，以分析吸收衬和边缘条件对挠曲模态衰减的影响。引导结构以结构传播模式事件以及流体传播模式事件退出。发现边缘条件和吸收性衬里的使用分别显着影响结构传播模式和流体传播模式的衰减。