Modal analysis of leakage-induced acoustic vibrations in different directions for leak detection and location in fluid-filled pipelines

The leakage-induced acoustic vibrations are guided by the pipelines and discretized into several modes. Different modes exhibit different dispersive behaviors and generate vibrations of different directions. In this study, the modal characteristics of acoustic vibrations in different directions are investigated theoretically and experimentally. The dispersive natures and the displacement distributions of the guided wave modes in fluid-filled pipelines are analyzed using the guided wave theory. Theoretical analysis predicts that the axial vibrations are dominated by a single non-dispersive longitudinal mode, while the radial and circumferential vibrations are dominated by more than one dispersive modes respectively in the frequency range 0-2.5kHz. Then the experimental investigations convince the theoretical predictions and demonstrate that the axial vibrations are dominated by an individual non-dispersive guided wave with small attenuation rate in the frequency region 0-2.5 kHz. These discoveries demonstrate that, at information acquisition stage, exclusively picking up the axial vibration can significantly improve leak detection and location in the pipelines compared to the conventional detection of the radial vibration.