Sediment transport in high-speed flows over a fixed bed: 2. Particle impacts and abrasion prediction
Sediment transport in high-speed flows over a fixed bed: 2. Particle impacts and abrasion prediction
复制标题
固定床上高速流动中的泥沙输送：2.颗粒冲击和磨损预测
DOI：
10.1002/esp.4132
复制
发表时间：
2017
期刊：
影响因子：
--
通讯作者：
R.M.
中科院分区：
文献类型：
--
作者：
Auel;C.;Albayrak;I.;Sumi;T.;Boes;R.M.
在低相对粗糙度高度的固定平面河床上，模拟高梯度非冲积山溪和水工结构，对超临界明渠水流的单床荷载颗粒冲击进行了实验研究。在广泛的水力参数和颗粒特性下，确定了颗粒的冲击特性（冲击速度、冲击角度、斯托克斯数、恢复和动摩擦系数）。颗粒冲击速度随颗粒速度的增大而增大，颗粒垂直冲击速度随输运阶段的增加而增大。颗粒撞击角和回弹角较低，且随输运阶段的增加而减小。颗粒与床层的碰撞分析表明，几乎没有粘性阻尼效应，且法向恢复系数高，超过1。正常和由此产生的斯托克斯数很高，并且高于粘性阻尼的临界阈值。这些结果归因于壁面附近的相干湍流结构，即具有抛射和扫掠事件的爆发运动，负责湍流的产生和粒子输运。切向恢复系数略低于1，动力摩擦系数低于冲积层数据，表明只有少量水平能量转移到冲积层。对Sklar和Dietrich（2004）建立的磨损预测模型进行了修正，该模型采用了新的涵盖不同床层构型的垂直冲击速度和跳跃长度方程。研究发现，硬材料（抗拉强度为10mpa）的磨损系数在kv~ 105之间变化，比Sklar和Dietrich模型迄今为止所假设的值低一个数量级。版权所有©2017 John Wiley & Sons， Ltd
Single bed load particle impacts were experimentally investigated in supercritical open channel flow over a fixed planar bed of low relative roughness height simulating high‐gradient non‐alluvial mountain streams as well as hydraulic structures. Particle impact characteristics (impact velocity, impact angle, Stokes number, restitution and dynamic friction coefficients) were determined for a wide range of hydraulic parameters and particle properties. Particle impact velocity scaled with the particle velocity, and the vertical particle impact velocity increased with excess transport stage. Particle impact and rebound angles were low and decreased with transport stage. Analysis of the particle impacts with the bed revealed almost no viscous damping effects with high normal restitution coefficients exceeding unity. The normal and resultant Stokes numbers were high and above critical thresholds for viscous damping. These results are attributed to the coherent turbulent structures near the wall region, i.e. bursting motion with ejection and sweep events responsible for turbulence generation and particle transport. The tangential restitution coefficients were slightly below unity and the dynamic friction coefficients were lower than for alluvial bed data, revealing that only a small amount of horizontal energy was transferred to the bed. The abrasion prediction model formed by Sklar and Dietrich in 2004 was revised based on the new equations on vertical impact velocity and hop length covering various bed configurations. The abrasion coefficientkvwas found to be vary aroundkv~ 105for hard materials (tensile strengthft> 1 MPa), one order of magnitude lower than the value assumed so far for Sklar and Dietrich's model. Copyright © 2017 John Wiley & Sons, Ltd.