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LIN Zhenhua,SONG Jinbao. 2014. Numerical studies on the degeneration of internal waves induced by an initial tilted pycnocline. Acta Oceanologica Sinica, 33(7):27-39
Numerical studies on the degeneration of internal waves induced by an initial tilted pycnocline
初始倾斜跃层所致内波的数值研究
Received:August 28, 2013  Revised:November 26, 2013
DOI:10.1007/s13131-014-0503-9
Key words:internal wave  numerical model  wave breaking  energy dissipation
中文关键词:  跃层,内波,数值模拟
基金项目:The Fund for Creative Research Groups by the National Natural Science Foundation of China under contract No. 41121064;the Strategic Priority Research Program of the Chinese Academy of Sciences under contract No. XDA11010104;the Open Fund of State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences under contract No. LTO1104.
Author NameAffiliationE-mail
LIN Zhenhua Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
Key Laboratory of Ocean Circulation and Waves (KLOCAW), Chinese Academy of Sciences, Qingdao 266071, China 
linzhenhuaouc@gmail.com 
SONG Jinbao Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
Key Laboratory of Ocean Circulation and Waves (KLOCAW), Chinese Academy of Sciences, Qingdao 266071, China 
 
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Abstract:
      The pycnocline in a closed domain is tilted by external wind forcing and tends to restore to a level position when the wind falls. An internal seiche oscillation exhibits if the forcing is weak, otherwise internal surge and internal solitary waves emerge, which serve as a link to cascade energy to small-scale processes. A two-dimensional non-hydrostatic code with a turbulence closure model is constructed to extend previous laboratory studies. The model could reproduce all the key phenomena observed in the corresponding laboratory experiments. The model results further serve as a comprehensive and reliable data set for an in-depth understanding of the related dynamical process. The comparative analyses indicate that nonlinear term favors the generation of internal surge and subsequent internal solitary waves, and the linear model predicts the general trend reasonably well. The vertical boundary can approximately reflect all the incoming waves, while the slope boundary serves as an area for small-scale internal wave breaking and energy dissipation. The temporal evolutions of domain integrated kinetic and potential energy are also analyzed, and the results indicate that about 20% of the initial available potential energy is lost during the first internal wave breaking process. Some numerical tactics such as grid topology and model initialization are also briefly discussed.
中文摘要:
      在外界风应力强迫作用形成的倾斜跃层在重力的作用下有恢复到水平的趋势,当外力作用较弱时候,层结流体界面为较弱的往复振荡,而当外力作用较强时,在这个过程中会生成内涌和内波,这提供了一种将能量从较大尺度向较小尺度传递的媒介。在本文中,我们建立了一个包含湍流封闭模型的二维非静力模型,来扩展前期实验研究的相关结果。数值模型可以用来得到前期实验中观测到的关键现象,模拟结果可以进一步提供前期实验中无法得到的各个物理量的定量信息,从而可以帮助我们更好理解这些过程。通过敏感性试验我们可以更好理解非线性在这个过程中的作用。垂直避免可以较好反射入射波,而倾斜边界处内波则发生较强烈的破碎和能量耗散过程。我们可以利用数值模型的结果研究整个关注区域能量随时间的变化趋势,分析结果表明,在第一组内波破碎的过程中大约有20%的初始有效重力位能损失。在文中我们也就一些数值方法如网格的拓扑结构和初始化方法作了相关讨论。
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