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<p>Flow-induced vibration and the resulting acoustic radiation are critical concerns for underwater pipeline systems, yet the mechanisms governing the spectral characteristics of radiated sound remain poorly understood, particularly for lightweight polymer pipes. This study investigates the acoustic radiation of a submerged polypropylene random (PPR) pipe subjected to internal water flow through experiments in an anechoic tank. A U-shaped pipe configuration was constructed, and acoustic signals were measured using a vector hydrophone 1 m from the pipe across 38 flow velocities ranging from 0.198 to 3.773&#xa0;m/s. The acoustic spectra across the flow velocities are consistently dominated by a stable frequency component at 73.2&#xa0;Hz, which remains invariant with flow velocity—a defining characteristic of the PPR pipe's acoustic response. At several discrete velocities (0.58, 0.66, 1.74, and 2.04&#xa0;m/s), the sound pressure RMS increases by nearly an order of magnitude, with over 99% of the acoustic energy concentrated at this single frequency-a hallmark of strong structural resonance. To explain this phenomenon, a theoretical model based on cylindrical-shell vibration theory with added-mass effects is developed to estimate the wet modal frequencies. The calculated wet natural frequency of the 16th bending mode is approximately 72.4 Hz, closely matching the experimentally observed dominant frequency (relative error 1.1%). This agreement reveals that the radiated sound is governed by high-order structural bending modes excited by turbulent pressure fluctuations in the internal flow. These findings elucidate a resonance mechanism underlying flow-induced acoustic radiation in underwater plastic pipelines and provide practical guidance for vibration and noise control in marine engineering applications.</p>

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Flow-induced acoustic radiation of a submerged PPR pipe is governed by high-order bending mode resonance

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月8日

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  • Jiayao Sun,
  • Shiqi Mo,
  • Oleg Gaidai

摘要

Flow-induced vibration and the resulting acoustic radiation are critical concerns for underwater pipeline systems, yet the mechanisms governing the spectral characteristics of radiated sound remain poorly understood, particularly for lightweight polymer pipes. This study investigates the acoustic radiation of a submerged polypropylene random (PPR) pipe subjected to internal water flow through experiments in an anechoic tank. A U-shaped pipe configuration was constructed, and acoustic signals were measured using a vector hydrophone 1 m from the pipe across 38 flow velocities ranging from 0.198 to 3.773 m/s. The acoustic spectra across the flow velocities are consistently dominated by a stable frequency component at 73.2 Hz, which remains invariant with flow velocity—a defining characteristic of the PPR pipe's acoustic response. At several discrete velocities (0.58, 0.66, 1.74, and 2.04 m/s), the sound pressure RMS increases by nearly an order of magnitude, with over 99% of the acoustic energy concentrated at this single frequency-a hallmark of strong structural resonance. To explain this phenomenon, a theoretical model based on cylindrical-shell vibration theory with added-mass effects is developed to estimate the wet modal frequencies. The calculated wet natural frequency of the 16th bending mode is approximately 72.4 Hz, closely matching the experimentally observed dominant frequency (relative error 1.1%). This agreement reveals that the radiated sound is governed by high-order structural bending modes excited by turbulent pressure fluctuations in the internal flow. These findings elucidate a resonance mechanism underlying flow-induced acoustic radiation in underwater plastic pipelines and provide practical guidance for vibration and noise control in marine engineering applications.