Rapid computation of sound transmission in fluid-filled pipes coupled with an outer elastic medium

Abstract

Determining the sound propagation characteristics of fluid-filled pipes is essential in acoustic stealth and leakage detection research. This study develops a rapid method for assessing the acoustic transmission properties of fluid-filled pipes under practical conditions involving an external medium. Initially, coupled equations for the fluid-filled pipe and the surrounding medium are established. Based on the dispersion characteristics, the influence of different external media on the propagation of the s = 1 wave mode is analyzed. Overall, the surrounding medium affects both wave speed and transmission loss within the pipe. Specifically, the added damping introduced by the external medium increases acoustic transmission loss. When the external medium exerts an axial force on the pipe, its axial natural frequency increases (by about a factor of 100 when embedded in soil compared to water), thereby suppressing resonant peaks in the transmission loss. The loading effect of the external medium also alters wave speed. When the pipe is embedded in soil, the low-frequency wave speed increases notably. A transfer matrix describing the relationship between variables at both ends of the pipe is derived using fluid pressure and displacement and pipe force and displacement. This model accounts for the external elastic medium, a feature frequently neglected in prior studies, to provide a more accurate representation of practical scenarios such as buried and subsea pipelines. Based on this matrix, a method for calculating transmission loss is developed, substantially reducing the time required to solve complex partial differential equations. The computed transmission loss aligns well with simulation data, validating the proposed method. Overall, the approach considerably enhances computational efficiency, making it suitable for engineering applications.