Analysis of dune erosion processes in large-scale flume experiments
Analysis of dune erosion processes in large-scale flume experiments
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DOI：
10.1016/j.coastaleng.2008.04.004
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发表时间：
2008-12
影响因子：
4.4
通讯作者：
J. T. D. Vries;M. V. Gent;D. Walstra;A. Reniers
中科院分区：
文献类型：
--
作者：
J. T. D. Vries;M. V. Gent;D. Walstra;A. Reniers
对不同波浪周期进行了大规模物理模型试验，以研究驱动沙丘侵蚀的物理过程。模型测试在沙丘暴露于极端浪涌和波浪条件下的水槽 (2DV) 中进行 [Van Gent, M.R.A., Van Thiel de Vries, J.S.M., Coeveld, E.M., De Vroeg, J.H.和 Van de Graaff, J., 2008。大规模沙丘侵蚀试验研究波浪周期的影响。海岸工程。 doi:10.1016/j.coastaleng.2008.04.003.]。在近岸区域对水压、流速和泥沙浓度进行了时间和空间上的详细测量。数据显示，短波和长波对于内部冲浪流体动力学都很重要。深度平均流量被引导至近海并朝着海岸线增加。相应的平均沉积物浓度朝沙丘面急剧上升（沙床附近高达 50 克/升）。沙丘表面平均沉积物浓度的急剧增加与最大波面坡度密切相关，而最大波面坡度又与压力梯度和近床波浪破碎引起的湍流耦合。分析表明，压力梯度仅部分地与流动加速度耦合，这表明后者不能总是用作第一个的替代。与床剪切应力相关的近床流量具有弱相关性。较大波浪周期的测试导致沙丘侵蚀量更大。在这些测试中，更多的波能（入射波和次重力波的组合）到达沙丘表面，但更重要的是，这种波能被更少的波耗散，从而产生更强烈的破波器和更陡的波前。因此，预计波浪破碎引起的近床湍流会增加，导致平均沉积物浓度显着升高（O（100％））。此外，平均流速相当，产生更大的近海定向沉积物输送能力。近海定向运输的增加仅部分地被与波浪内过程相关的波浪相关的陆上运输能力的同时增加所补偿，导致沙丘侵蚀率的净增加。
Large-scale physical model tests were conducted with different wave periods to examine the physical processes driving dune erosion. The model tests have been carried out in a flume (2DV) with a sandy dune exposed to extreme surge and wave conditions [Van Gent, M.R.A., Van Thiel de Vries, J.S.M., Coeveld, E.M., De Vroeg, J.H. and Van de Graaff, J., 2008. Large-scale dune erosion tests to study the effect of wave periods. Coastal Engineering. doi:10.1016/j.coastaleng.2008.04.003.]. Detailed measurements in time and space of water pressure, flow velocities and sediment concentrations were performed in the near shore area. The data revealed that both short- and long waves are important to inner surf hydrodynamics. Depth averaged flows are directed offshore and increase towards the shore line. The corresponding mean sediment concentrations rise sharply towards the dune face (up to 50 g/l near the bed). The strong increase in the mean sediment concentration towards the dune face correlates well with the maximum wave surface slope which in turn is coupled to both the pressure gradient and the near-bed wave-breaking induced turbulence. Analysis shows that the pressure gradient is only partially coupled to the flow acceleration suggesting that the latter cannot always be used as a proxy for the first. Weak correlation is obtained with the near-bed flows related to the bed shear stress. Tests with a larger wave period resulted in a larger dune erosion volume. During these tests more wave energy (combined incident and infragravity waves) reached the dune face, but more importantly, this wave energy is dissipated by fewer waves resulting in more intense wave breakers and steeper wave fronts. It is therefore expected that the wave-breaking induced near-bed turbulence increases resulting in significantly higher (O(100%)) mean sediment concentrations. In addition the mean flow velocities are comparable, yielding a substantially larger offshore directed sediment transport capacity. This increase in offshore directed transport is only partially compensated by a concurrent increase in the wave related onshore transport capacity associated with intrawave processes, resulting in a net increase in the dune erosion rate.