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《Using velocity-induced acoustic oscillations as a standard ruler at cosmic dawn》

  • 来源专题：声学研究所所级服务
  • 编译者： ioalib2
  • 发布时间：2019-10-12

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  • 《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.
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    • Science News from research organizationsScientists observe how acoustic interactions change materials at the atomic level. Date: September 24, 2019 Source: DOE/Argonne National Laboratory Summary: By using sound waves, scientists have begun to explore fundamental stress behaviors in a crystalline material that could form the basis for quantum information technologies. Share:FULL STORY When exposed to stress and strain, materials can display a wide range of different pr...
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