Acoustic Characteristics Analysis of Double-Layer Liquid-Filled Pipes Based on Acoustic–Solid Coupling Theory

Abstract

Based on the theory of acoustic–solid coupling, the phase velocity-thickness product of a double-layer liquid-filled pipeline is analyzed, and the dispersion relationship between angular frequency and wavenumber–thickness product is analyzed, providing a theoretical basis for ultrasonic guided wave detection. The wave number analytical expression of the double-layer liquid-filled pipeline is constructed, and the dispersion relationship of the double-layer liquid-filled pipeline under different frequency–thickness products and wavenumber–thickness products is calculated through parameter scanning. The dispersion curves of the double-layer liquid-filled pipeline are numerically analyzed in the domains of pressure acoustics, solid mechanics, and acoustic–solid coupling. The numerically simulated dispersion curves show high consistency with the analytically calculated dispersion curves. The analysis of the phase velocity frequency–thickness product indicates that the axial mode dispersion curves of the pipe wall decrease with the increase in frequency–thickness product in the coupling domain, and then tend to be flat and intersect with the radial mode dispersion curves in the coupling domain; these intersection points cannot be used for ultrasonic guided wave detection. The T(0,1) mode dispersion curve in the coupling domain of the pressure acoustics domain remains smooth from low frequency to high frequency. It is found that the dispersion curves of the phase velocity frequency–thickness product, angular frequency wavenumber–thickness product, and the acoustic pressure distribution map of the double-layer liquid-filled pipeline based on acoustic–solid coupling can provide theoretical support for ultrasonic guided wave detection of pipelines.