The morphodynamics of a swash event on an erodible beach
The morphodynamics of a swash event on an erodible beach
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DOI：
10.1017/jfm.2014.610
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发表时间：
2014-12
影响因子：
3.7
通讯作者：
Fangfang Zhu;N. Dodd
中科院分区：
文献类型：
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作者：
Fangfang Zhu;N. Dodd
摘要：本文首次采用高精度数值解，将一维浅水和河床演化方程与悬沙平流方程耦合，从而包括河床和/或悬浮荷载，用于研究初始平面可蚀海滩上的两个冲刷事件：Peregrine & Williams (J.流体力学；，第440卷，2001年，第391-399页)和一个单独的波浪接近海滩。采用特征化方法对方程进行求解，并对数值模型进行了验证。Peregrine & Williams [J.流体力学。]， vol. 440, 2001, pp. 391-399)只产生轻微改变的冲刷流，这取决于海滩流动性和沉积物响应时间；一系列相似的最终海滩变化模式导致了不同的海滩移动。悬质和床质输运具有明显的形态动力学特征。对于孤立波，产生一个反冲洗孔（Hibberd & Peregrine， J.流体力学）。，第95卷，1979，第323-345页)。这种形态动力学钻孔最初在海上传播，并导致了海滩床阶的形成（Larson & Sunamura， J.沉积岩石学，第63卷，1993年，第495-500页），主要是由于床载运输。它的高度与床载迁移率直接相关，也与床层摩擦系数密切相关。对这一层阶的冲击动力学进行了解释和说明。利用现场数据量化了床层和悬浮载荷的流动性，并尝试将预测与自然海滩上的单一冲刷事件的测量联系起来。平均预测的床层变化幅度为2毫米左右，在床阶处最大床层变化可达约10厘米。
Abstract A high-accuracy numerical solution, coupling one-dimensional shallow water and bed-evolution equations, with, for the first time, a suspended sediment advection equation, thereby including bed and/or suspended load, is used to examine two swash events on an initially plane erodible beach: the event of Peregrine & Williams (J. Fluid Mech., vol. 440, 2001, pp. 391–399) and that of a solitary wave approaching the beach. Equations are solved by the method of characteristics, and the numerical model is verified. Full coupling of suspended load to beach change for Peregrine & Williams (J. Fluid Mech., vol. 440, 2001, pp. 391–399) yields only slightly altered swash flows, depending on beach mobility and sediment response time; a series of similar final beach change patterns results for different beach mobilities. Suspended- and bed-load transport have distinct morphodynamical signatures. For the solitary wave a backwash bore is created (Hibberd & Peregrine, J. Fluid Mech., vol. 95, 1979, pp. 323–345). This morphodynamical bore propagates offshore initially, and leads to the creation of a beach bed step (Larson & Sunamura, J. Sedimentary Petrology, vol. 63, 1993, pp. 495–500), primarily due to bed-load transport. Its height is directly related to bed-load mobility, and also depends strongly on the bed friction coefficient. The shock dynamics of this bed step is explained and illustrated. Bed- and suspended-load mobilities are quantified using field data, and an attempt is made to relate predictions to measurements of single swash events on a natural beach. Average predicted bed change magnitudes across the swash are of the order of 2 mm, with maximum bed changes of up to approximately 10 cm at the bed step.