Model-data comparisons of shear waves in the nearshore
Model-data comparisons of shear waves in the nearshore
复制标题
近岸剪切波模型数据比较
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
T. Herbers
中科院分区：
文献类型：
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作者：
T. Noyes;R. Guza;F. Feddersen;S. Elgar;T. Herbers
[1]对横波的观测结果进行了比较，横波的沿岸传播曲流平均周期为几分钟，沿岸波长为几百米，与基于非线性浅水方程数值解的模式预测结果进行了比较。该模型（根据Ozkan-Haller和Kirby(1999)）假设了沿岸均匀性和暂时稳定的波浪强迫，忽略了波流相互作用、涡流混合和（非线性）底部阻力系数的空间变化。虽然观测到的和模拟的横波速度谱的形状不同，而且均方根速度波动仅在约3的因子范围内一致，但观测到的横波（海底以上~ 0.5-1.0 m）和模拟的（垂直整合的）横波的跨岸结构的各个方面在质量上是相似的。在平均沿岸流(V)强、剪切波能量大的冲浪带内，观测到的和模拟的剪切波沿岸相速度一致，接近V和Clin（线性不稳定模态的相速度），这与之前的结果一致。在较远的近海，在V较弱且观测和模拟的剪切波能级衰减迅速的地方，模拟和观测到的C偏离了Clin，接近较弱的沿岸流V。模拟表明，较近海岸的强剪切流脱落的沿岸涡旋平流可能有助于近海剪切波相速度的降低。与观测结果相似，模拟的横波速度波动和沿岸横波速度波动的幅度大致相等，模拟的涡度在整个冲浪带上都有变化。
[1] Observations of shear waves, alongshore propagating meanders of the mean alongshore current with periods of a few minutes and alongshore wavelengths of a few hundred meters, are compared with model predictions based on numerical solutions of the nonlinear shallow water equations. The model (after Ozkan-Haller and Kirby (1999)) assumes alongshore homogeneity and temporally steady wave forcing and neglects wave-current interactions, eddy mixing, and spatial variation of the (nonlinear) bottom drag coefficient. Although the shapes of observed and modeled shear wave velocity spectra differ, and root-mean-square velocity fluctuations agree only to within a factor of about 3, aspects of the cross-shore structure of the observed (∼0.5–1.0 m above the seafloor) and modeled (vertically integrated) shear waves are qualitatively similar. Within the surf zone, where the mean alongshore current (V) is strong and shear waves are energetic, observed and modeled shear wave alongshore phase speeds agree and are close to both V and Clin (the phase speed of linearly unstable modes) consistent with previous results. Farther offshore, where V is weak and observed and modeled shear wave energy levels decay rapidly, modeled and observed C diverge from Clin and are close to the weak alongshore current V. The simulations suggest that the alongshore advection of eddies shed from the strong, sheared flow closer to shore may contribute to the offshore decrease in shear wave phase speeds. Similar to the observations, the modeled cross- and alongshore shear wave velocity fluctuations have approximately equal magnitude, and the modeled vorticity changes sign across the surf zone.