PSI to turbulence during internal wave beam refraction through the upper ocean pycnocline
PSI to turbulence during internal wave beam refraction through the upper ocean pycnocline
复制标题
PSI 到内波束折射穿过上层海洋密斜层期间的湍流
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
S. Sarkar
中科院分区：
文献类型：
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作者：
B. Gayen;S. Sarkar
利用大涡模拟方法研究了半日波内波束与上层海洋密度跃层的非线性相互作用。在通过密度跃层的折射过程中，光束经历参数亚谐不稳定性（PSI），形成频率为（1/2）M2的波。三维大涡模拟能够获得新的结果，量化通过PSI的湍流路径。PSI产生的次谐波的垂直尺度小一个数量级，容易破碎。对流不稳定引发了向湍流的转变，而切变的产生维持了这一转变。在次谐波路径上的点处，湍流在（1/2）M2频率下被调制。光束由于PSI、反射谐波和管道波而遭受显著的劣化，使得只有约30%的入射能量由主反射光束传输。
A numerical study based on large eddy simulation (LES) is performed to investigate the nonlinear interaction of a semidiurnal (M2) internal wave beam with an upper ocean pycnocline. During refraction through the pycnocline, the wave beam undergoes parametric subharmonic instability (PSI) with formation of waves with (1/2)M2 frequency. The three‐dimensional LES enables new results that quantify the route to turbulence through PSI. The subharmonic waves generated from PSI have an order of magnitude smaller vertical scale and are susceptible to wave breaking. Convective instability initiates transition to turbulence, while shear production maintains it. Turbulence at points in the subharmonic wave paths is modulated at (1/2)M2 frequency. The beam suffers substantial degradation owing to PSI, reflected harmonics and ducted waves so that only about 30% of the incoming energy is transported by the main reflected beam.