Acoustic waves have been widely used to inspect pipeline defects, including leakage, blockage and corrosion etc. The time-domain excitation of guided waves in the fluid/solid coupled pipeline system has rarely been studied theoretically. This requires the incorporation of a source term in the coupled system. This article introduces a finite element based numerical model to study the excitation of guided waves in the coupled system with a sound source either in the fluid or on the pipe wall. A compatible pair of time-domain Perfectly Matched Layers (PMLs) have been proposed to absorb pipe end reflections in the elastic wall and in the fluid respectively. These fluid/solid PML numerical formulations are coupled and the implementation of the coupling is introduced. The numerical model is validated against an enlarged model without PML, and excellent agreement has been achieved. The numerical model shows that the dominant excited wave mode is a fluid type wave mode when the sound source is a fluid source or a radial elastic line source. However, the dominant excited wave mode is a structure type wave mode when the sound source is an axial elastic line source.

声波已被广泛用于检测管道缺陷，包括泄漏、堵塞和腐蚀等。在流固耦合管道系统中导波的时域激励理论研究很少。这需要在耦合系统中加入源项。本文介绍了一种基于有限元的数值模型来研究耦合系统中导波在流体中或管壁上与声源的激发。已经提出了一对兼容的时域完美匹配层 (PML)，以分别吸收弹性壁和流体中的管端反射。这些流体/固体PML数值公式进行了耦合，并介绍了耦合的实现。数值模型针对没有 PML 的放大模型进行验证，并达成了很好的协议。数值模型表明，当声源为流体源或径向弹性线源时，主要激发波模式为流体型波模式。然而，当声源为轴向弹性线源时，主要的激发波模式是结构型波模式。