Three-dimensional instability of internal gravity wave beams
Three-dimensional instability of internal gravity wave beams
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内重力波梁三维不稳定性
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
T. Akylas
中科院分区：
文献类型：
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作者：
Takeshi Kataoka;T. Akylas
内部重力波梁的三维不稳定性。R. Akylas马萨诸塞州理工学院机械工程系trakylas@mit.edu摘要基于Kataoka和Akylas（2015）导出的束-平均流相互作用方程，研究了孤立和相互作用内部重力波束对三维扰动的稳定性。这些二维状态被发现是不稳定的调制不稳定性，一个纯粹的无粘机制，以及由于沿沿着光束传播方向的粘性衰减所带来的流效应的结果。介绍内部重力波束（IGWB）是具有一般空间轮廓的时间谐波平面波。这种扰动是具有连续垂直分层的流体中内波运动的各向异性的表现，并且可以被视为各向同性介质中的圆柱波前的类似物。IGWB具有相当大的地球物理意义，因为它们形成海洋内部潮汐的骨干，也可以由于雷暴而在大气中出现。IGWB的大多数先前的研究都集中在二维（2D）扰动在无粘Boussinesq流体与恒定的浮力频率。在这些流动条件下，孤立的均匀IGWB恰好是精确的非线性状态，与光束轮廓无关（Tabaei和Akylas 2003），并且可能由于光束碰撞而发生与边界处的反射有关的显著非线性相互作用（Tabaei等人，2005）。然而，IGWB的三维（3D）传播从根本上不同于其2D对应物：3D的变化使能量的共振转移，通过雷诺应力的作用，流动平均垂直涡度，导致IGWB和其诱导的平均流之间的强非线性耦合。这种3D相互作用机制由两个耦合的非线性振幅方程（Kataoka和Akylas 2015，以下简称KA）渐近控制，这解释了在实验室实验中观察到的伴随强制3D IGWB的强水平平均流（Bordes等人，2012）。根据这一理论模型，平均流量第八届国际研讨会。8月29日至9月，美国圣地亚哥，2016年1月
Three-dimensional Instability of Internal Gravity Wave Beams Takeshi Kataoka and T. R. Akylas Department of Mechanical Engineering, Massachusetts Institute of Technology trakylas@mit.edu Abstract The stability of isolated and interacting internal gravity wave beams to three-dimensional perturbations is studied, based on the beam–mean-flow interaction equations derived in Kataoka and Akylas (2015). These two-dimensional states are found to be unstable as a result of modulational instability, a purely inviscid mechanism, as well as due to a streaming effect brought about by viscous attenuation along the beam propagation direction. Introduction Internal gravity wave beams (IGWB) are time-harmonic plane waves with general spatial profile. Such disturbances are manifestations of the anisotropy of internal wave motion in fluids with continuous vertical stratification, and may be regarded as the analogues of cylindrical wavefronts in isotropic media. IGWB are of considerable geophysical interest, as they form the backbone of the internal tide in oceans and can also arise in the atmosphere due to thunderstorms. Most prior studies of IGWB have focused on two-dimensional (2D) disturbances in an inviscid Boussinesq fluid with constant buoyancy frequency. Under these flow conditions, isolated uniform IGWB happen to be exact nonlinear states irrespective of the beam profile (Tabaei and Akylas 2003), and significant nonlinear interactions may occur in connection with reflections at boundaries and possibly due to collisions of beams (Tabaei et al. 2005). However, the three-dimensional (3D) propagation of IGWB differs fundamentally from its 2D counterpart: 3D variations enable resonant transfer of energy, through the action of Reynolds stresses, to the flow mean vertical vorticity, resulting in strong nonlinear coupling between an IGWB and its induced mean flow. This 3D interaction mechanism is governed asymptotically by two coupled nonlinear amplitude equations (Kataoka and Akylas 2015, hereinafter referred to as KA), which account for the observed strong horizontal mean flow accompanying a forced 3D IGWB in laboratory experiments (Bordes et al. 2012). According to this theoretical model, the mean flow VIII th Int. Symp. on Stratified Flows, San Diego, USA, Aug. 29 - Sept. 1, 2016
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