Radiation of acoustic and gravity waves and propagation of boundary waves in the stratified fluid from a time-varying bottom boundary
Radiation of acoustic and gravity waves and propagation of boundary waves in the stratified fluid from a time-varying bottom boundary
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DOI：
10.1017/s0022112009005953
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发表时间：
2009-05-25
影响因子：
3.7
通讯作者：
Watada, Shingo
中科院分区：
文献类型：
--
作者：
Watada, Shingo
在频率波数域中研究了重力分层等温可压缩无粘半无限流体中线性化声-重力波的能量流动、辐射和边界波的传播。阻抗Z是海底垂直位移与其上方流体压力的比值，是海底边界波动频率和水平波数（ω，k）的函数。底部边界处Z的振幅和相位将（omega，k）坐标划分为波型区域。与纯声波或重力波的情况相反，Z的相位是连续的，但是在传播波和底部处的捕获波之间的状态边界上快速变化，除了兰姆波分支沿着其振幅是无限的并且相位跨越其跳跃π。Z的相位决定了通过变形的底部边界对流体做功的效率，示出了在Z的相位接近+/-pi/2的状态边界附近从底部向上的波能流减少。为了精确建模流体中的压力波以及声波和重力波的能量流，其源自具有与流体中的声速相当的表观相速度的时间相关的底表面变形，有必要包括对阻抗Z的（Ω，k）的依赖性。
Energy flow and radiation of linearized acoustic-gravity waves and propagation of boundary waves in a gravitationally stratified isothermal compressible inviscid semi-infinite fluid from a time-varying bottom boundary are investigated in the frequency-wavenumber domain. Impedance Z, the ratio of the bottom vertical displacement to the fluid pressure above it, is a function of the frequency and horizontal wavenumber (omega, k) of the bottom boundary undulation. The amplitude and phase of Z at the bottom boundary divide the (omega, k) coordinates into wave-type regimes. In contrast to the pure acoustic or gravity wave case, the phase of Z is continuous but changes quickly across the regime boundaries between the propagating waves and trapped waves at the bottom, except for the Lamb wave branch along which the amplitude is infinite and across which the phase jumps by pi. The phase of Z determines the efficiency of the work against the fluid by the deforming bottom boundary, showing reduced upward wave-energy flow from the bottom near the regime boundaries in which the phase of Z approaches +/-pi/2. For precise modelling of pressure waves and the energy flow of acoustic and gravity waves in the fluid originating from a time-dependent bottom-surface deformation with an apparent phase velocity comparable to the speed of sound in the fluid, it is necessary to include the dependency on (omega, k) of impedance Z.