登录
 机构网站
  1. 首页
  2. 情报产品
  3. 快讯详情

《Nonlinear acoustic propagation in bubbly liquids: Multiple scattering, softening and hardening phenomena 》

  • 来源专题：声学研究所所级服务
  • 发布时间：2016-04-11

  • The weakly nonlinear propagation of acoustic waves in monodisperse bubbly liquids is investigated numerically. A hydrodynamic model based on the averaged two-phase fluid equations is coupled with the Rayleigh-Plesset equation to model the dynamics of bubbles at the local scale. The present model is validated in the linear regime by comparing with the Foldy approximation. The analysis of the pressure signals in the linear regime highlights two resonance frequencies: the Minnaert frequency and a multiple scatteringresonance that strongly depends on the bubble concentration. For weakly nonlinear regimes, the generation of higher harmonics is observed only for the Minnaert frequency. Linear combinations between the Minnaert harmonics and the multiple scatteringresonance are also observed. However, the most significant effect observed is the appearance of softening-hardening effects that share some similarities with those observed for sandstones or cracked materials. These effects are related to the multiple scatteringresonance. Downward or upward resonance frequency shifts can be observed depending on the characteristic of the incident wave when increasing the excitation amplitude. It is shown that the frequency shift can be explained assuming that the acoustic wave velocity depends on a law different from those usually encountered for sandstones or cracked materials.

92浏览量
原文链接
相关报告

  • 《Numerical analysis of three-dimensional acoustic propagation in the Catoche Tongue: The Journal of the Acoustical Society of America: Vol 138, No 4》
    • 来源专题：水声领域信息监测
    • 编译者：ioalib
    • 发布时间：2016-12-20
    • Analysis of modeled time series data is presented to provide insight into propagation physics of horizontally refracted sound in the Catoche Tongue region of the Gulf of Mexico. The analysis is motivated by the observation of out-of-plane arrivals in measured time series data. In particular, the extended duration of the refracted arrivals is shown to be caused by interaction with multiple locations along the steep sides of the Tongue. Comparison of the modeled time series is made to previous work by Sturm [J. Acoust. Soc. Am. 117(3), 1058–1079 (2005)], who examined the frequency dependence of out-of-plane modal arrivals for the wedge-shaped ocean.
    100浏览量
    原文链接

  • 《Impacts of environment-dependent acoustic propagation on passive acoustic monitoring of cetaceans》
    • 来源专题：水声领域信息监测
    • 发布时间：2016-11-21
    • Significant effort has been made over the last few decades to develop automated passive acoustic monitoring (PAM) systems capable of classifying cetaceans at the species level; however, these systems often require tuning when deployed in different environments. Anecdotal evidence suggests that this requirement to adjust a PAM system’s parameters is partially due to differences in the propagation characteristics. The environment-dependent propagation characteristics create variation in how a cetacean vocalization is distorted after it is emitted. If this is not accounted for, it could reduce the accuracy and precision of automated PAM systems. An aural classifier developed at Defence R&D Canada (DRDC) has successfully been used for inter-species discrimination of cetaceans. It achieves accurate results by using perceptual signal features that model the features employed by the human auditory system. To quantify the impacts of propagation on the perceptual features, an experiment was conducted in which bowhead and humpback whale vocalizations were transmitted over 1-20 km ranges during a two-day sea trial in the Gulf of Mexico. The experimental results will be presented and strategies will be discussed for training the classifier so that it is capable of operating in numerous acoustic environments with minimal adjustment of the classifier’s parameters.
    89浏览量
    原文链接