Generation of Langmuir circulation for nonaligned wind stress and the Stokes drift
Generation of Langmuir circulation for nonaligned wind stress and the Stokes drift
复制标题
生成非定向风应力和斯托克斯漂移的朗缪尔环流
DOI：
10.1029/97jc00460
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发表时间：
1997
影响因子：
--
通讯作者：
V. Polonichko
中科院分区：
文献类型：
--
作者：
V. Polonichko
朗缪尔细胞的增长率计算从不同方向的风，波，细胞以及用于描述波流相互作用的无量纲参数的各种值的线性稳定性分析。这些参数可以是斯托克斯漂移/摩擦速度比和剪切比Sr，其描述斯托克斯漂移剪切和平均欧拉剪切的相对强度。当风和波浪对齐时，增长率总体上最大。对于斯托克斯漂移和风之间的给定角度（失准角），用于最大增长的单元轴的方向位于风和波浪之间，并且主要由（1）失准角和（2）剪切比确定。对于后者的固定值，生长最快的细胞的方向（优先细胞方向）几乎是独立的一个其他无量纲参数，这可能是斯托克斯漂移/摩擦速度比或朗缪尔数。随着斯托克斯漂移切变相对于平均切变的增加，增长最快的细胞的方向向波方向移动得更近，反之亦然。然而，虽然对于小Sr，优先单元方向靠近风，但是对于合理大的Sr，它不与波浪对齐。当风和波浪不对齐并且斯托克斯漂移切变和平均切变具有相同的量级时，单元以与单元轴成一定角度侧向漂移，其速度与在约0.7倍单元深度的深度处的平均欧拉电流的幅度相当。漂移幅度随着失准角的增加而增加，并且对于较大的剪切比值而言更大。当风和波浪朝向相反的方向时，没有不稳定的来源，并且细胞被阻尼。
The growth rate of Langmuir cells is calculated from a linear stability analysis for different orientations of wind, waves, and cells as well as for various values of the dimensionless parameters describing wave-current interaction. These parameters could be the Stokes drift/friction velocity ratio and the shear ratio Sr which describes the relative strength of the Stokes drift shear and mean Eulerian shear. The growth rate is maximal overall when wind and waves are aligned. For a given angle between the Stokes drift and the wind (the misalignment angle), the direction of the cell axis for maximal growth lies between wind and waves and is mainly determined by (1) the misalignment angle and (2) the shear ratio. For a fixed value of the latter, the orientation of the fastest growing cells (the preferential cell direction) is nearly independent of the one other dimensionless parameter which could be the Stokes drift/friction velocity ratio or the Langmuir number. The direction of the fastest growing cells shifts closer toward the wave direction as the Stokes drift shear increases relative to the mean shear and vice versa. However, while the preferential cell direction lies close to the wind for small Sr, it does not align with the waves for reasonably large Sr. When wind and waves are not aligned and the Stokes drift shear and the mean shear are of the same order, the cells drift sideways at an angle to the cell axes, with a speed which is comparable with the magnitude of the mean Eulerian current at a depth of approximately 0.7 times the cell depth. The drift amplitude increases as the misalignment angle increases and is larger for larger values of the shear ratio. When wind and waves are oriented in the opposite directions, there is no source of instability, and the cells are damped.