Mutual Interaction between Surface Waves and Langmuir Circulations Observed in Wave-Resolving Numerical Simulations
Mutual Interaction between Surface Waves and Langmuir Circulations Observed in Wave-Resolving Numerical Simulations
复制标题
波解析数值模拟中观察到的表面波与朗缪尔环流之间的相互作用
DOI：
10.1175/jpo-d-19-0288.1
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发表时间：
2020
影响因子：
3.5
通讯作者：
Yutaka Yoshikawa
中科院分区：
文献类型：
--
作者：
Yasushi Fujiwara;Yutaka Yoshikawa
对理想条件下的单色表面波和朗缪尔环流进行了波分解模拟，研究了波流相互作用的动力学。当弗劳德数（在表面施加的风应力的摩擦速度和波相速度的比率）是大的，波成为折射的顺风射流与LC和成为振幅调制的顺风方向。在这种情况下，使用Craik-Leibovich（CL）方程与规定的水平均匀的斯托克斯漂移分布的模拟被发现低估的LC的强度。涡量收支分析表明，水平剪切的斯托克斯漂移波调制引起的风驱动的涡量向下风方向倾斜，加强LC，导致波被调制。这种效应在CL方程中是不能再现的，除非由LC调制的波的Stokes漂移被规定。这种强化机制类似于CL 1机制，因为斯托克斯漂移的水平剪切起着关键作用，但它更有可能发生，因为这种相互作用中的剪切是由LC自动产生的，而CL 1机制中的剪切仅在两个交叉波之间的特定相位关系保持锁定许多周期时才保留。
Wave-resolving simulations of monochromatic surface waves and Langmuir circulations (LCs) under an idealized condition are performed to investigate the dynamics of wave–current mutual interaction. When the Froude number (the ratio of the friction velocity of wind stress imposed at the surface and wave phase speed) is large, waves become refracted by the downwind jet associated with LCs and become amplitude modulated in the crosswind direction. In such cases, the simulations using the Craik–Leibovich (CL) equation with a prescribed horizontally uniform Stokes drift profile are found to underestimate the intensity of LCs. Vorticity budget analysis reveals that horizontal shear of Stokes drift induced by the wave modulation tilts the wind-driven vorticity to the downwind direction, intensifying the LCs that caused the waves to be modulated. Such an effect is not reproduced in the CL equation unless the Stokes drift of the waves modulated by LCs is prescribed. This intensification mechanism is similar to the CL1 mechanism in that the horizontal shear of the Stokes drift plays a key role, but it is more likely to occur because the shear in this interaction is automatically generated by the LCs whereas the shear in the CL1 mechanism is retained only when a particular phase relation between two crossing waves is kept locked for many periods.