Finite-amplitude instabilities of thin internal wave beams: experiments and theory
Finite-amplitude instabilities of thin internal wave beams: experiments and theory
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薄内波束的有限振幅不稳定性：实验和理论
DOI：
10.1017/jfm.2020.682
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发表时间：
2020
影响因子：
3.7
通讯作者：
T. Akylas
中科院分区：
文献类型：
--
作者：
Boyu Fan;T. Akylas
本文对分层流体中局部约束重力内波束的失稳机理进行了实验和理论研究。使用在光束传播方向上谐波振荡的水平圆柱作为强制力，使得可以产生空间轮廓包括不超过单个波长的相干有限振幅内光束。对于强迫振幅超过一定的阈值取决于驱动频率，这样的薄波光束被观察到经历一个不稳定性，涉及两个亚谐波扰动与波包样的空间结构。虽然它与小振幅正弦波的三元共振不稳定性（TRI）有相似之处，但目前的不稳定性不能用TRI理论预测，因为初级波不是近单色的，而是包含宽带波数谱。与此相反，实验观察是在良好的协议与一个正式的线性稳定性分析的基础上Floquet理论的预测。最后，实验证据表明，横向梁的变化引起的水平平均流的流型和大大制服的不稳定性。
Abstract A joint experimental and theoretical study is made of instability mechanisms of locally confined internal gravity wave beams in a stratified fluid. Using as forcing a horizontal cylinder that is oscillated harmonically in the direction of beam propagation makes it possible to generate coherent finite-amplitude internal wave beams whose spatial profile comprises no more than a single wavelength. For forcing amplitude above a certain threshold depending on the driving frequency, such thin wave beams are observed to undergo an instability that involves two subharmonic perturbations with wavepacket-like spatial structure. Although it bears resemblance to the triadic resonant instability (TRI) of small-amplitude sinusoidal waves, the present instability cannot be predicted by TRI theory as the primary wave is not nearly monochromatic, but instead contains broadband wavenumber spectrum. In contrast, the experimental observations are in good agreement with the predictions of a formal linear stability analysis based on Floquet theory. Finally, experimental evidence is presented that transverse beam variations induce a horizontal mean flow of the streaming type and greatly subdue the instability.
影响因子：
--
作者：
T. Hibiya;M. Nagasawa;Y. Niwa
通讯作者：
T. Hibiya;M. Nagasawa;Y. Niwa
影响因子：
3.7
作者：
T.Jamin;T.Kataoka;T.Dauxois;and T.R. Akylas
通讯作者：
and T.R. Akylas
关于三维内部重力波束和诱发的大尺度平均流
影响因子：
2.7
作者：
T.Kataoka;T.R.Akylas
通讯作者：
T.R.Akylas