The Impact of Turbulence on Hydroacoustic Waves

TL;DR

This study investigates how turbulence affects hydroacoustic waves, revealing that turbulence influences wave amplitude and phase, with effects varying periodically with frequency and not primarily driven by temperature changes.

Contribution

It provides a detailed analysis of turbulence's impact on hydroacoustic waves, including phase shifts, amplitude variations, and frequency-dependent effects, extending prior research with new experimental insights.

Findings

Turbulence alters both amplitude and phase of hydroacoustic waves.

Temperature rise from friction is not the main cause of amplitude changes.

Wave effects depend periodically on frequency, with thresholds for turbulence influence.

Abstract

Building upon our first paper [Hu, K.X, & Hu, Y. J. (2025). Hydroacoustic Absorption and Amplification by Turbulence, arXiv:2512.07920], the present work conducts a more in-depth investigation into the impact of turbulence on hydroacoustic waves. The study includes the influences of temperature, unsteady laminar flow, standing wave effects, the alteration of phase, the variation of amplification factor with frequency, and the temporal evolution of the acoustic wave. Experiments indicate that the temperature rise caused by friction between the turbulent flow and the pipe wall does not significantly affect the acoustic wave, and therefore is not the primary cause of changes in wave amplitude. When two transducers are placed opposite each other, the acoustic waves can be regarded as a superposition of traveling waves and standing waves. When the pump is shut down after the pipe flow has stabilized, the temporal evolution of the acoustic waves during the subsequent turbulence decay process can be classified into six types. In addition to altering the amplitude, turbulence also changes the phase of waves. The total phase shift of the acoustic wave along the entire pipe equals the sum of the phase shifts in each segment. Both the amplification factor and the phase shift due to turbulence vary periodically with frequency. Acoustic waves with frequencies below and above specific thresholds are essentially unaffected by turbulence. These findings suggest that the interaction between hydroacoustic waves and turbulence constitutes stimulated absorption and emission in water.