Generation of internal solitary waves over a large sill: From Knight Inlet to Luzon Strait
Generation of internal solitary waves over a large sill: From Knight Inlet to Luzon Strait
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DOI：
10.1002/2016jc012206
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发表时间：
2017-02
影响因子：
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通讯作者：
Zhiwu Chen;Y. Nie;Jieshuo Xie;Jiexin Xu;Yinghui He;S. Cai
中科院分区：
文献类型：
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作者：
Zhiwu Chen;Y. Nie;Jieshuo Xie;Jiexin Xu;Yinghui He;S. Cai
利用完全非线性、非流体静力学数值模型研究了奈特进水口护岸上游内部孤波（ISW）的产生。虽然上游水力跃迁启动了内孤波的产生，而且水力跃迁和上游影响都有助于内孤波的产生，但研究发现，上游影响占主导地位，水力跃迁对于内孤波的最终产生并非必要。减小潮汐作用力或上游陡坡宽度可使水流处于亚临界状态（即水力跃变消失），ISW 可通过上游影响引起的长波扰动的非线性陡变而产生。增大潮汐作用力或上游陡坡宽度可能会产生水力跃层，阻挡强大的上游传播扰动。水力跃层随后会变成湍流孔，并在潮汐减弱时分散成一列 ISW。潮汐作用力的进一步增强可能会将湍流孔向下游冲刷，并在退潮末期向上游发射一列 ISW。通过将分层强度降低 1 个数量级，近岸流处于跨临界状态，ISW 在靠岸斜坡上共振产生。此外，还讨论了与吕宋海峡内潮释放机制和非稳态利波模型之间的联系。本研究对奈特湾的 ISW 生成过程有了更深入的了解，并确定了奈特湾的生成机制与吕宋海峡的生成机制之间的联系。
A fully nonlinear, nonhydrostatic numerical model is utilized to investigate the generation of Internal Solitary Waves (ISWs) upstream of the Knight Inlet sill. While an upstream hydraulic jump initiates the ISW generation and both hydraulic jump and upstream influence contribute to the generation, it is found that upstream influence is dominant and the hydraulic jump is not necessary for the ultimate generation of ISWs. Decreasing the tidal forcing or upstream sill width may render the flow subcritical (i.e., the hydraulic jump disappears) and ISWs can be generated by nonlinear steepening of long wave disturbances induced by upstream influence. Increasing the tidal forcing or upstream sill width may generate a hydraulic jump blocking strong upstream propagating disturbances. The jump subsequently becomes a turbulent bore and later disperses into a train of ISWs as the tide relaxes. Further increase in the tidal forcing may sweep the turbulent bore downstream and a train of ISWs is emitted upstream toward the end of waning tide. By reducing the stratification strength by 1 order of magnitude, the near-sill flow is in the transcritical regime and ISWs are resonantly generated over the lee side slope. Connections to the internal tide release mechanism at Luzon Strait and to the unsteady lee wave model are also discussed. The present work provides some more insights into the ISW generation process at Knight Inlet and the connection between the generation mechanism at Knight Inlet and that at Luzon Strait is identified.