Analysis of a simplification strategy in a nonhydrostatic model for surface and internal wave problems |
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| Authors: | Jinghua Zhang Wensheng Jiang Xueqing Zhang |
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| Institution: | 1.Key Laboratory of Marine Environment and Ecology of Ministry of Education, Ocean University of China, Qingdao 266100, China2.Tianjin Research Institute for Water Transport Engineering, Ministry of Transport., Tianjin 300456, China3.Physical Oceanography Laboratory/Qingdao Collaborative Innovation Center of Marine Science and Technology, Ocean University of China, Qingdao 266100, China4.Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China |
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| Abstract: | This paper examines the simplification strategy of retaining only the nonhydrostatic effect of local acceleration in a three-dimensional fully nonhydrostatic model regarding the submesoscale wave phenomenon in the ocean. Elaborate scale analysis of the vertical component of the Reynold-averaged Navier–Stokes (RANS) equation was performed, confirming the rationalization of this simplification. Then, the simplification was implemented in a RANS equation-based nonhydrostatic model NHWAVE (nonhydrostatic WAVE) to make a simplified nonhydrostatic model. Numerical examples were taken to test its performance, including surface sinusoidal waves propagating on an idealized East China Sea topography, tidally induced internal lee waves and small-scale solitary waves. The results show that in a considerably wide range of nonlinear strengths, the simplified nonhydrostatic model can obtain similar results as those in the fully nonhydrostatic model, even for smaller-scale solitary waves. Nonlinearity influences the applicability of the simplification. The stronger the nonlinearity is, the worse the simplified model describes the nonhydrostatic phenomenon. In general, the simplified nonhydrostatic model can simulate surface waves better than internal waves. Improvement of computational efficiency in the simplified nonhydrostatic model is reasonable, reducing the central processing unit time duration in the fully nonhydrostatic model by 16.4%–20.6%. The specially designed algorithm based on the simplified nonhydrostatic equation can remarkably reduce the computational time. |
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| Keywords: | simplification of nonhydrostatic model submesoscale wave internal lee wave |
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