Circulation in the nearshore region, which is critical for material transport along the coast and between the surf zone and the inner shelf, includes strong vortical motions. The horizontal length scales and vertical structure associated with vortical motions are not well documented on alongshore-variable beaches. Here, a three-dimensional phase-resolving numerical model, Simulating WAves till SHore (SWASH), is compared with surfzone waves and flows on a barred beach, and is used to investigate surfzone eddies. Model simulations with measured bathymetry reproduce trends in the mean surfzone circulation patterns, including alongshore currents and rip current circulation cells observed for offshore wave heights from 0.5 to 2.0 m and incident wave directions from 0 to 15° relative to shore normal. The length scales of simulated eddies, quantified using the alongshore wavenumber spectra of vertical vorticity, suggest that increasing wave directional spread intensifies small-scale eddies ((10) m). Simulations with bathymetric variability ranging from alongshore uniform to highly alongshore variable indicate that large-scale eddies ((100) m) may be enhanced by surfzone bathymetric variability, whereas small-scale eddies ((10) m) are less dependent on bathymetric variability. The simulated vertical dependence of the magnitude and mean length scale (centroid) of the alongshore wavenumber spectra of vertical vorticity and very low-frequency (f ≈ 0.005 Hz) currents is weak in the outer surf zone, and decreases toward the shoreline. The vertical dependence in the simulations may be affected by the vertical structure of turbulence, mean shear, and bottom boundary layer dynamics.

中文翻译：

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沿岸可变禁止海滩上的三维洋流和涡流模型

近岸区域的环流对于沿海岸以及海浪区和内陆架之间的物质运输至关重要，其中包括强烈的涡旋运动。与涡旋运动相关的水平长度尺度和垂直结构在沿岸多变的海滩上没有得到很好的记录。在此，将三维相位解析数值模型 Simulating Waves until SHore (SWASH) 与冲浪带波浪和禁止海滩上的流动进行比较，并用于研究冲浪带涡流。使用测得的水深测量的模型模拟再现了平均海浪带环流模式的趋势，包括在 0.5 至 2.0 m 的海上波高和相对于海岸法线的 0 至 15° 的入射波方向观察到的沿岸流和离岸流环流单元。模拟涡流的长度尺度，(10) 米)。水深变化范围从沿岸均匀到高度沿岸变量的模拟表明，大尺度涡流 ( (100) m) 可能会因冲浪带水深变化而增强，而小尺度涡旋 ( (10) m) 对水深变化的依赖性较小。垂直涡度和极低频 ( f  ≈ 0.005 Hz) 流的沿岸波数谱的幅度和平均长度尺度（质心）的模拟垂直依赖性在外海浪带中较弱，并且朝着海岸线减小。模拟中的垂直依赖性可能受湍流垂直结构、平均剪切和底部边界层动力学的影响。