Observations and predictions of run‐up
Observations and predictions of run‐up
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启动过程的观察和预测
DOI：
10.1029/96jc02432
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发表时间：
1996
影响因子：
--
通讯作者：
R. Guza
中科院分区：
文献类型：
--
作者：
B. Raubenheimer;R. Guza
对于一个显着的范围内的离岸波浪条件和前滨斜坡，运行的观测相比，现有的数值模型的基础上的深度平均一维非线性浅水方程的半经验公式和预测钻孔破碎波耗散和二次底摩擦。数值模型初始化的海面高程和跨岸速度的时间序列观察到80厘米的平均水深（约50米离岸的平均海岸线）在一个平缓的倾斜海滩和175厘米的水深（100米离岸的海岸线）在一个陡峭的凹海滩。爬高是用一堆电阻丝在海拔5，10，15，20和25厘米以上，并平行于海滩面测量。在海涌频率（标称0.05 < f ≤ 0.18 Hz）下，上升能量受到向岸传播波的碎波区耗散的限制，使得将离岸波高增加到阈值以上基本上不会增加预测或观察到的海涌上升偏移（例如，启动是“饱和的”）。现有的半经验饱和度公式是最一致的观察和数值模型预测的运行偏移最近的床。相反，在亚重力频率（0.004 < f ≤ 0.05 Hz），碎波带耗散相对较弱，来自海滩表面的反射较强（例如，饱和度公式不适用），助跑偏移随着离岸波高的增加而近似线性地增加。数值模型还准确地预测了助跑的舌状形状导致助跑测量对钢丝高度的敏感性。例如，助跑偏移和平均垂直超高（高于离岸静水水位）随着缆线高程的降低而增加，波浪上涌期间助跑舌的连续变薄可能导致在不同缆线高程处测量的助跑偏移之间存在较大的相位差。数值模型模拟表明，助跑测量超过几厘米以上的床不能用来推断，甚至在助跑舌头的流体速度的迹象。
For a significant range of offshore wave conditions and foreshore slopes, run-up observations are compared to semiempirical formulations and predictions of an existing numerical model based on the depth-averaged one-dimensional nonlinear shallow water equations with bore-like breaking wave dissipation and quadratic bottom friction. The numerical model is initialized with time series of sea surface elevation and cross-shore velocity observed in 80 cm mean water depth (approximately 50 m offshore of the mean shoreline) on a gently sloping beach and in 175 cm water depth (100 m offshore of the shoreline) on a steep concave beach. Run-up was measured with a stack of resistance wires at elevations 5, 10, 15, 20, and 25 cm above and parallel to the beach face. At sea swell frequencies (nominally 0.05 < f ≤ 0.18 Hz), run-up energy is limited by surf zone dissipation of shoreward propagating waves so that increasing the offshore wave height above a threshold value does not substantially increase the predicted or observed sea swell run-up excursions (e.g., run-up is “saturated”). Existing semiempirical saturation formulations are most consistent with the observations and numerical model predictions of run-up excursions nearest the bed. In contrast, at infragravity frequencies (0.004 < f ≤ 0.05 Hz) where surf zone dissipation is relatively weak and reflection from the beach face is strong (e.g., saturation formulas are not applicable), the run-up excursions increase approximately linearly with increasing offshore wave height. The numerical model also accurately predicts that the tongue-like shape of the run-up results in sensitivity of run-up measurements to wire elevation. For instance, run-up excursions and mean vertical superelevation (above the offshore still water level) increase with decreasing wire elevation, and continuous thinning of the run-up tongue during the wave uprush can result in large phase differences between run-up excursions measured at different wire elevations. Numerical model simulations suggest that run-up measured more than a few centimeters above the bed cannot be used to infer even the sign of the fluid velocities in the run-up tongue.