Parametric Amplification in the Dynamic Radiation Force of Acoustic Waves in Fluids

Acoustic amplification and bifurcation in a moving fluid

The quasi-accumulation solutions of acoustic wave in a moving fluid are obtained by using the Lagrange parameter variation method to solve the differential equation that describes the interaction between the acoustic waves and the flow. The results show that the nonlinear interaction causes the period-doubling followed by the odd multiple half-period bifurcation and all order subharmonics are generated subsequently, of which the amplitudes depend not only on the acoustic Mach number but also on the Mach number of the flow. The latter result indicates that the acoustic wave has been amplified b…

湍流对水声吸收与放大作用的研究

Hydroacoustic Absorption and Amplification by Turbulence

本研究通过实验发现，水下湍流在高频范围内可显著吸收或放大声波，最大衰减或放大超60%，且无谱展宽，表明存在未被传统理论解释的新机制。

Parametric Instabilities in Shallow Water Magnetohydrodynamics Of Astrophysical Plasma in External Magnetic Field

This letter discusses rotating magnetohydrodynamics (MHD) of a thin layer of astrophysical plasma. To describe a thin plasma layer with a free surface in a vertical external magnetic field we use the shallow water ap- proximation. The presence of a vertical magnetic field essentially changed the wave processes dynamics in astrophysical plasma compared to the neu- tral uid and plasma layer in a thoroidal magnetic field. In present case thre are three-waves nonlinear interactions. Using the asymptotic mul- tiscale we deduced nonlinear wave packets interaction equations: three magneto-Poincare wa…