On the breaking of internal solitary waves at a ridge
On the breaking of internal solitary waves at a ridge
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DOI：
10.1017/s0022112002001556
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发表时间：
2002-10
影响因子：
3.7
通讯作者：
J. K. Sveen;Yakun Guo;P. Davies;J. Grue
中科院分区：
文献类型：
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作者：
J. K. Sveen;Yakun Guo;P. Davies;J. Grue
通过实验研究了两层层状流体系统中凹陷内孤立波的传播及其在底部山脊上的变形。在三个基准位置，即上游、下游和山脊上方，测量了波浪剖面、密度场和速度场。实验的波幅范围为上层深度的0.2-1.9倍，下层与上层之比为3.0-8.5。山脊坡度在0.1~0.33之间变化，最大山脊高度为较厚流体层的三分之二。在脊线上的流动可分为：(I)底脊对内孤立波的传播和空间结构影响不大的情况，(Ii)内孤立波被脊线的阻塞效应严重扭曲的情况(虽然没有发生破波)，以及(Iii)内孤立波在遇到和越过底脊时被破坏的情况。对导致波浪破碎的过程进行了详细的描述。已发现，当下层的流体速度超过定义在脊顶的局部非线性波速的0.7时，就会发生破裂。破碎条件还用入射波的幅度、层厚比和隆起的相对高度来表示。根据实验的输入参数可以确定破波的大小。已发现发射的波总是由超前脉冲(孤立波)和紧随其后的色散波列组成。只有在山脊处发生破裂时，(孤立)波的幅度才会显著减小。在破裂较强的情况下，产生模式二的内波。
An experimental laboratory study has been carried out to investigate the propagation of an internal solitary wave of depression and its distortion by a bottom ridge in a two-layer stratified fluid system. Wave profiles, density fields and velocity fields have been measured at three reference locations, namely upstream, downstream and over the ridge. Experiments have been performed with wave amplitudes in the range 0.2– 1.9 times the depth of the upper layer, and a ratio between the lower and the upper layer in the range 3.0–8.5. The ridge slope was varied from 0.1 to 0.33 and the maximum ridge height was two-thirds of the thicker fluid layer. Over the ridge, the flow has been classified into: (i) cases when the bottom ridge has little influence on the propagation and spatial structure of the internal solitary wave, (ii) cases where the internal solitary wave is significantly distorted by the blocking effect of the ridge (though no wave breaking occurs), and (iii) cases for which the internal solitary wave is broken as it encounters and passes over the bottom ridge. A detailed description of the processes leading to wave breaking is given. Breaking has been found to take place when the fluid velocity in the lower layer exceeds 0.7 of a local nonlinear wave speed, defined at the top of the ridge. The breaking condition is also expressed in terms of the amplitude of the incident wave, the layer thickness ratio and the relative height of the ridge. The wave breaking can be determined from the input parameters of the experiment. The transmitted waves have been found to always consist of a leading pulse (solitary wave) followed by a dispersive wavetrain. The (solitary) wave amplitude is significantly reduced only when breaking takes place at the ridge. Internal waves of mode two are generated in cases with strong breaking.