A Froude‐scaled model of a bedrock‐alluvial channel reach: 1. Hydraulics
A Froude‐scaled model of a bedrock‐alluvial channel reach: 1. Hydraulics
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基岩冲积河道河段的弗劳德比例模型： 1. 水力学
DOI：
10.1002/2015jf003706
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
T. Hoey
中科院分区：
文献类型：
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作者：
R. Hodge;T. Hoey
尽管水流在确定沉积物输送和随之而来的侵蚀的速率和模式方面很重要，但对基岩冲积河流水力学的控制知之甚少。为了测量基岩冲积河道内的水力学，我们使用地面激光扫描和 3D 打印开发了 1:10 Froude 比例的 18 × 9 m 基岩冲积河河段实验室模型。在报告的实验中，在河道内 18 个位置处记录了 5 次不同排放的水深和流速。来自水槽中沉积物覆盖的运行的附加数据用于评估沉积物覆盖的水力影响；配套文件中分析了这些运行中沉积物斑块的沉积和侵蚀。在我们的数据中（1）流速和弗劳德数的空间变化随着流量的增加而增加； (2) 在较高流量下，整体流动阻力和弗劳德数变得与流量无关； (3) 局部流速和雷诺应力与某些（但不是大多数）排放处的局部河床地形范围相关； (4) 在较低流量时，局部地形会引起垂直流结构和较慢的速度，但这些影响在较高流量时会减弱； (5)床层和沉积物粗糙度的线性组合与局部流速之间存在关系。这些结果证明了基岩地形对局部和河段尺度流动条件的控制，但需要来自具有不同地形的基岩冲积河道的空间分布水力数据来概括这些发现。
The controls on hydraulics in bedrock‐alluvial rivers are relatively poorly understood, despite the importance of the flow in determining rates and patterns of sediment transport and consequent erosion. To measure hydraulics within a bedrock‐alluvial channel, we developed a 1:10 Froude‐scaled laboratory model of an 18 × 9 m bedrock‐alluvial river reach using terrestrial laser scanning and 3‐D printing. In the reported experiments, water depth and velocity were recorded at 18 locations within the channel at each of five different discharges. Additional data from runs with sediment cover in the flume were used to evaluate the hydraulic impact of sediment cover; the deposition and erosion of sediment patches in these runs are analyzed in the companion paper. In our data (1) spatial variation in both flow velocity and Froude number increases with discharge; (2) bulk flow resistance and Froude number become independent of discharge at higher discharges; (3) local flow velocity and Reynolds stress are correlated to the range of local bed topography at some, but not most, discharges; (4) at lower discharges, local topography induces vertical flow structures and slower velocities, but these effects decrease at higher discharges; and (5) there is a relationship between the linear combination of bed and sediment roughness and local flow velocity. These results demonstrate the control that bedrock topography exerts over both local and reach‐scale flow conditions, but spatially distributed hydraulic data from bedrock‐alluvial channels with different topographies are needed to generalize these findings.