A conceptual model of pore-space blockage in mixed sediments using a new numerical approach, with implications for sediment bed stabilization
A conceptual model of pore-space blockage in mixed sediments using a new numerical approach, with implications for sediment bed stabilization
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DOI：
10.1007/s00367-015-0399-1
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发表时间：
2015-01
影响因子：
2.1
通讯作者：
G. Bartzke;K. Huhn
中科院分区：
文献类型：
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作者：
G. Bartzke;K. Huhn
在混合沉积物床中，由于不同的结构和/或其他粒度参数，抗侵蚀性相对于由均匀沉积物组成的床会发生变化，对孔隙水流量的影响难以通过模拟技术量化。为了克服这一困难，三维数值模型的开发使用有限差分法（FDM）的流动模型与离散元法（DEM）的颗粒模型相结合。主要目的是以高空间分辨率调查在不同流速下沉积物-水界面和简化沉积物床浅层地下单个颗粒运动开始期间发生的物理过程。将增加比例的极细砂（D50=0.08 mm）混合到粗砂基质（D50=0.6 mm）中以模拟混合沉积物床，从实验1中的纯粗砂床（0重量%细粒）开始，并进行实验2（6.5重量%细粒）、实验3（10.5重量%细粒）和实验4（28.7重量%细粒）。所有的混合床在预定的流速U1 -5=10-30 cm/s的范围内变化时测试其侵蚀行为。实验表明，随着细粒含量的增加，较小的颗粒越来越多地填充较大颗粒之间的空间。因此，孔隙水流入沉积物越来越受阻，孔隙水流速降低，因此可用于夹带颗粒的流动动量降低。这些研究结果描绘在一个新的概念模型，增强沉积物床稳定。
In mixed sediment beds, erosion resistance can change relative to that of beds composed of a uniform sediment because of varying textural and/or other grain-size parameters, with effects on pore water flow that are difficult to quantify by means of analogue techniques. To overcome this difficulty, a three-dimensional numerical model was developed using a finite difference method (FDM) flow model coupled with a distinct element method (DEM) particle model. The main aim was to investigate, at a high spatial resolution, the physical processes occurring during the initiation of motion of single grains at the sediment–water interface and in the shallow subsurface of simplified sediment beds under different flow velocities. Increasing proportions of very fine sand (D50=0.08 mm) were mixed into a coarse sand matrix (D50=0.6 mm) to simulate mixed sediment beds, starting with a pure coarse sand bed in experiment 1 (0 wt% fines), and proceeding through experiment 2 (6.5 wt% fines), experiment 3 (10.5 wt% fines), and experiment 4 (28.7 wt% fines). All mixed beds were tested for their erosion behavior at predefined flow velocities varying in the range ofU1-5=10–30 cm/s. The experiments show that, with increasing fine content, the smaller particles increasingly fill the spaces between the larger particles. As a consequence, pore water inflow into the sediment is increasingly blocked, i.e., there is a decrease in pore water flow velocity and, hence, in the flow momentum available to entrain particles. These findings are portrayed in a new conceptual model of enhanced sediment bed stabilization.