On the trapping of wave energy round islands
On the trapping of wave energy round islands
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DOI：
10.1017/s0022112067001181
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发表时间：
1967-09
影响因子：
3.7
通讯作者：
M. Longuet-Higgins
中科院分区：
文献类型：
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作者：
M. Longuet-Higgins
研究表明，岛屿可以以类似于原子核捕获粒子的方式捕获长波能量。捕捉到的波的频率形成一个离散的集合，由岛屿的形状和周围海床的轮廓决定。如果在很远的距离处的深度趋向于一个恒定值，那么被捕获的模式一定会泄漏一些能量到无穷远，尽管由此产生的衰减速率可能非常小。捕获模式的初始能量可以从相同频率的入射辐射或从锐脉冲中吸收。文中还详细讨论了直线脉冲入射圆形岛屿的具体例子。地球自转的影响是将围绕岛屿向相反方向传播的一对波的频率分开。频率的分裂在波中产生慢拍，就像在任何固定点看到的那样。岛上的轻微不对称导致每对渐进模式之间缓慢的能量交换。在南大洋麦夸里岛的长波记录中，出现了周期为6分钟、拍周期约为3小时的规律振荡，这表明了本研究的意义。
It is shown that islands can trap long-wave energy in a way similar to the capture of a particle by an atomic nucleus. The frequencies of the captured waves form a discrete set, being determined by the shape of the island and the contours of the surrounding sea bed. If the depth at great distances tends to a constant value, the trapped modes must leak some energy to infinity, though the consequent rate of decay may be exceedingly small. The initial energy of the trapped modes may be absorbed from incident radiation of the same frequency or from a sharp pulse. The particular example of a rectilinear pulse incident on a circular island is discussed in some detail. The effect of the rotation of the Earth is to split the frequencies of a pair of waves progressing in opposite directions round the island. The splitting of the frequencies produces slow beats in the waves as seen at any fixed point. Slight asymmetry in the island induces a slow exchange of energy between each pair of progressive modes. The present investigation was suggested by the occurrence of regular oscillations having a period of 6 min and a beat period of about 3 h in long-wave records taken at Macquarie Island, in the Southern Ocean.