Intra-swash hydrodynamics and sediment flux for dambreak swash on coarse-grained beaches
Intra-swash hydrodynamics and sediment flux for dambreak swash on coarse-grained beaches
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DOI：
10.1016/j.coastaleng.2016.03.004
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发表时间：
2016-06
影响因子：
4.4
通讯作者：
T. O'Donoghue;G. Kikkert;D. Pokrajac;N. Dodd;R. Briganti
中科院分区：
文献类型：
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作者：
T. O'Donoghue;G. Kikkert;D. Pokrajac;N. Dodd;R. Briganti
本文报道了在粗沙滩涂和砾石滩涂上进行的冲淤型冲淤试验，测量了冲淤内的水动力和泥沙通量。用PIV和LIF分别测量流速和深度；利用泥沙捕集器测量流域内泥沙通量。Kikkert et al.（2013）将实测的水动力与不动的、渗透性的河床实验进行了比较，结果表明，河床的流动性会影响冲刷水动力，与相应的不动海滩的最大升力相比，两种海滩的最大升力都减少了约8%。在给定位置测量到的冲刷带内泥沙通量在钻孔到达时具有高通量的特征，随后在冲升过程中迅速衰减，在水流反转前的某个时间变为零。对于砾石滩，反冲沙通量小到可以忽略不计，而对于沙质滩，反冲沙通量随着水流向海滩的加速而缓慢增加，并在最大反冲流速时达到峰值。采用Meyer-Peter和m<s:1> ller床荷载输运公式计算的冲刷带内泥沙通量，以测量的水动力作为输入，并使用Swart和Colebrook公式估计的河床剪应力，与测量的冲刷带内通量的差值在2因子之内。计算通量与实测值的一致性在沙质滩优于砾石滩，冲升滩优于反冲滩。对于沙滩，总冲积和总反冲积的计算值与实测值吻合较好。对于砾石滩，计算和测量的上冲体积呈现相似的趋势，但计算的反冲体积高估了实验中观察到的（可忽略的）体积。
The paper reports on dambreak-type swash experiments in which intra-swash hydrodynamics and sediment flux are measured for swash on a coarse sand beach and a gravel beach. Flow velocity and depth are measured using PIV and LIF respectively; the intra-swash sediment flux is measured using sediment traps. Comparison of measured hydrodynamics with the immobile, permeable bed experiments of Kikkert et al. (2013) indicates that bed mobility impacts on the swash hydrodynamics, reducing the maximum run-up by approximately 8% for both beaches, compared to the maximum run-up on the corresponding immobile beach. The measured intra swash sediment flux at a given location is characterised by high flux at the moment of bore arrival, followed by rapid decay during uprush, becoming zero at some time before flow reversal. For the gravel beach, the backwash sediment flux is negligibly small, while for the sand beach the backwash flux increases slowly as the flow accelerates down the beach, and peaks at about the time of maximum backwash velocity. Intra-swash sediment flux calculated using the Meyer-Peter and Müller bed load transport formula, with measured hydrodynamics as input and bed shear stress estimated using both the Swart and Colebrook formulae, is within a factor 2 of the measured intra-swash flux. The agreement between the calculated and measured flux is better for the sand beach than for the gravel beach, and better for uprush than for backwash. For the sand beach there is good agreement between calculated and measured total uprush and total backwash sediment volumes. The agreement is less good for the gravel beach, for which calculated and measured uprush volumes show a similar trend but the calculated backwash volumes over-estimate the (negligible) volumes observed in the experiments.