Research on the wave transmission characteristics of a flexible chamber inserted in the fluid-filled elastic pipeline

In the acoustic calculations of pneumatic pipeline systems, it is commonly assumed that the walls of the pipeline are rigid. It leads to the development of various acoustic theories based on rigid wall. However, in situations involving high-density fluids or thin-walled structures, the propagation of waves in the pipeline becomes complex due to the strong vibroacoustic coupling. In such cases, the wave transmission characteristics calculation methods based on the rigid wall assumption are no longer applicable. This paper employs the pipeline waveguide theory to estimate the wave transmission characteristics in the presence of complex wave behavior within the pipeline. Once the accuracy of the proposed method has been verified, the wave responses of a flexible chamber inserted in the fluid-filled elastic pipeline are analyzed. The analysis shows that the lowest-order fluid-type waves and the lowest-order longitudinal extension waves are found to propagate in the pipeline. The incident lowest-order fluid-type wave and its transmitted wave of the same mode can be successfully separated from other waves. The elasticity of the pipe wall can significantly affect the acoustic characteristics of an expansion chamber. Nevertheless, significant disparities in the wave amplitudes and limited sampling pose challenges to accurate calculations of the transmission loss.