The characteristics of billows generated by internal solitary waves
The characteristics of billows generated by internal solitary waves
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DOI：
10.1017/jfm.2016.823
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发表时间：
2017-01
影响因子：
3.7
通讯作者：
M. Carr;James Franklin;S. King;P. Davies;J. Grue;D. Dritschel
中科院分区：
文献类型：
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作者：
M. Carr;James Franklin;S. King;P. Davies;J. Grue;D. Dritschel
本文采用室内与数值相结合的方法，研究了与破碎内孤立波有关的剪切诱导倾覆巨浪的时空发展。在实验室中，通过锁交换机制产生这些波，并通过等高线-平流半拉格朗日方法进行了数值模拟。确定了每种情况下单个波浪的性质（最大达到高度、崩塌时间、生长速率、速度、波长、索普标度），并对波浪相互作用过程进行了研究和分类。对于宽阔平坦的波浪，其特征与平行剪切流相似，但对于非共轭流动极限的波浪，其波浪特性受到空间变化的波致剪切流的影响。波浪陡度和波幅对确定波浪之间发生的相互作用的类型以及是否可以阻止波浪倾覆具有至关重要的影响。给出了波浪(i)彼此独立演化，（ii）彼此配对，（iii）相互吞没/夹带以及（iv）不能完全倾覆的例子。结果表明，波浪可以达到的垂直范围（以及相关的索普尺度）取决于波浪的振幅，但一旦达到给定的振幅，其值就会饱和。有趣的是，这个振幅小于共轭流动极限振幅。波浪上形成的波浪的数量与波长有关；在给定的分层中，短波比长波支持更少但更大的波浪。
The spatial and temporal development of shear-induced overturning billows associated with breaking internal solitary waves is studied by means of a combined laboratory and numerical investigation. The waves are generated in the laboratory by a lock exchange mechanism and they are simulated numerically via a contour-advective semi-Lagrangian method. The properties of individual billows (maximum height attained, time of collapse, growth rate, speed, wavelength, Thorpe scale) are determined in each case, and the billow interaction processes are studied and classified. For broad flat waves, similar characteristics are seen to those in parallel shear flow, but, for waves not at the conjugate flow limit, billow characteristics are affected by the spatially varying wave-induced shear flow. Wave steepness and wave amplitude are shown to have a crucial influence on determining the type of interaction that occurs between billows and whether billow overturning can be arrested. Examples are given in which billows (i) evolve independently of one another, (ii) pair with one another, (iii) engulf/entrain one another and (iv) fail to completely overturn. It is shown that the vertical extent a billow can attain (and the associated Thorpe scale of the billow) is dependent on wave amplitude but that its value saturates once a given amplitude is reached. It is interesting to note that this amplitude is less than the conjugate flow limit amplitude. The number of billows that form on a wave is shown to be dependent on wavelength; shorter waves support fewer but larger billows than their long-wave counterparts for a given stratification.