A unified erosion formulation for fine sediments
A unified erosion formulation for fine sediments
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DOI：
10.1016/s0025-3227(01)00201-8
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发表时间：
2001-09
期刊：
影响因子：
2.9
通讯作者：
L. Sanford;J. Maa
中科院分区：
文献类型：
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作者：
L. Sanford;J. Maa
不同的细颗粒泥沙输运模型通常采用非常不同的、经常不相容的公式来描述底泥的表面侵蚀。在本文中，我们发展了一个简单的扩展的标准线性侵蚀公式，允许它用于描述I类(深度受限)侵蚀或II类(无限)侵蚀，这两种行为之间可以无缝过渡。该配方是根据侵蚀深度或侵蚀泥沙质量来预测的。假设临界应力随深度的局部恒定增长率和侵蚀常数与界面含沙量成正比，该模型预测了在施加每个新的剪应力步骤后，在I型侵蚀试验中经常观察到的指数衰减侵蚀速率。预测的衰减率与单位过剩应力的侵蚀速率乘以临界应力随深度增加的速率成正比。通过重新分析Maa等人提出的数据集来测试该公式。(1998)描述了在马里兰州巴尔的摩港进行的现场侵蚀试验，结果总体良好。时变力作用下冲刷方程的解表明，冲刷行为受控于切应力变化率与可侵蚀泥沙耗竭速率之比。如果剪应力变化的时间尺度与泥沙流失的时间尺度相比较长，则侵蚀速率由剪应力增加的时间速率与临界应力增加的深度速率相平衡(类型I性态)控制。如果剪应力变化的时间尺度比泥沙流失的时间尺度短，则侵蚀速率由底部剪应力与临界剪应力的瞬时差值控制(第II类行为)。提出了一种在泥沙数值模型中实现的通用算法。
Different models of fine sediment transport often employ very different, frequently incompatible formulations for surface erosion of bottom sediment. In this paper, we develop a simple extension of the standard linear erosion formulation that allows it to be used to describe either Type I (depth-limited) erosion or Type II (unlimited) erosion, with a seamless transition between the two behaviors. The formulation is cast in terms of either the depth of erosion or eroded sediment mass. Assuming a locally constant rate of increase in critical stress with depth and direct proportionality between the erosion constant and sediment concentration at the interface, the model predicts the exponentially decaying erosion rate often observed in Type I erosion tests after application of each new shear stress step. The predicted decay rate is proportional to the rate of erosion per unit excess stress times the rate of increase in critical stress with depth. The formulation is tested by re-analyzing the data set presented by Maa et al. (1998) describing in situ erosion tests in Baltimore Harbor, MD, with generally favorable results. Solutions of the erosion formulation with time varying forcing show that erosion behavior is controlled by the ratio of the rate of change of shear stress to the rate of depletion of erodible sediment. If the time scale of shear stress change is long compare to the time scale of sediment depletion, then erosion rate is controlled by the time rate of increase in shear stress balanced against the depth rate of increase in critical stress (Type I behavior). If the time scale of shear stress change is short compared to the time scale of sediment depletion, then erosion rate is controlled by the instantaneous difference between bottom shear stress and critical shear stress (Type II behavior). A general algorithm for implementation in numerical sediment transport models is presented.