A Reynolds-averaged simulation of costal Langmuir cells in a constant depth and variable depth water column

Langmuir turbulence in the coastal ocean is driven by winds and waves and is characterized by Langmuir cells (LCs) that can span the full depth of the water column in unstratified settings. A solution strategy based on Reynolds averaging is introduced, relying on the coherency and persistence of full-depth LCs. Here these cells are resolved by the Reynolds-averaged formulation, treated as a secondary component to the wind and/or pressure gradient-driven primary flow. Two uniform depth simulations performed with the Reynolds-averaged formulation are submitted following the large-eddy simulation setup of Tejada-Martínez & Grosch (2007). Both cases are characterized by a turbulent Langmuir number (Lat) of 0.7 (see Tejada-Martinez and Grosch, 2007) and a wavelength of 6H and 3H (where H is the water column depth), parameters related to the wind and wave forcing conditions in the simulations. The case with the wavelength of 6*H and Lat = 0.7 corresponds to wind stress of 0.1 N/m^2, the significant wavelength of 90 m, and significant wave amplitude of 0.6 m measured in the field observations of full-depth Langmuir cells by Gargett & Wells (2007) in 15 meters depth. The variable depth simulation consists of a domain with depth varying between H=15 meters and H=7.5 meters over a 1 km distance along the x-direction. The depth is constant along the y-direction. The wind and waves are aligned in the y-direction. The wind stress, the wave amplitude, and the wavelength are fixed at 0.1 N/m^2, 0.6 m and 90 m (6*H = 6*15 m). The wave frequency is computed from the dispersion relation. The dataset consists of three-dimensional fields of velocity, turbulent kinetic energy, and epsilon values as a function of time for the uniform depth cases (160, 320, 480, and 640 minutes and 14 hours) and variable depth cases (1450, 290, 435, and 580 minutes). A detailed Readme document describes the model domain, forcing, and solution methods and provides snapshots of vertical velocity fluctuations.近岸海域的朗缪尔湍流（Langmuir turbulence）由风和海浪驱动，其特征为朗缪尔胞（Langmuir cells, LCs）：在非层化环境中，此类胞状结构可贯穿整个水柱深度。本研究引入了一种基于雷诺平均（Reynolds averaging）的求解策略，其依托于全水深朗缪尔胞的相干性与持续性。在此框架下，雷诺平均公式可解析这些胞状结构，并将其视为由风及/或压强梯度驱动的主流的次级分量。本研究基于Tejada-Martínez与Grosch（2007）的大涡模拟（large-eddy simulation, LES）设置，开展了两项采用雷诺平均公式的等水深模拟。两组模拟的湍流朗缪尔数（turbulent Langmuir number, Lat）均为0.7（详见Tejada-Martinez与Grosch, 2007），波长分别为6H与3H（其中H为水柱深度），上述参数与模拟中的风、浪强迫条件相关。其中波长为6H且Lat=0.7的模拟工况，其风应力为0.1 N/m²，有效波长为90米，有效波幅为0.6米，该参数匹配了Gargett与Wells（2007）在15米水深开展的全水深朗缪尔胞野外观测结果。变水深模拟的计算域沿x方向1公里范围内水深在H=15米与H=7.5米之间变化，沿y方向水深保持恒定。风与浪均沿y方向布置，风应力、波幅与波长分别固定为0.1 N/m²、0.6米与90米（6H=6×15米）。波浪频率通过频散关系计算得到。本数据集包含等水深工况（对应时刻为160、320、480、640分钟及14小时）与变水深工况（对应时刻为1450、290、435及580分钟）下的三维速度场、湍动能场与ε场随时间的演化数据。配套的详细Readme文档对计算域、强迫条件与求解方法进行了说明，并提供了垂直速度脉动的快照图。