Exploring turbulence-sediment dynamics for river erosion control

申请人提议研究湍流及其与水道中沉积物的相互作用。河床湍流引起河床泥沙冲刷和沉积，影响河道的稳定性。河道不稳定对防洪、改善航运和安全使用河内建筑物的河流工程方案的有效性产生不利影响。沉积物-水界面区域的流动动力学非常复杂且了解甚少。本研究的目的是加深对复杂流动动力学的理解。在河流汇合处，两条不同流速的水流合并形成一条河道，合并的水流具有速度剪切的特征。相关的涡度会导致流体动力学不稳定和湍流的发展。湍流涡流能够冲刷河床上的沉积物颗粒并将其扫向下游。过去的研究主要集中在流入流体之间的湍流混合，假设床层摩擦力可以忽略不计。该假设对于流经浅汇合处的流量无效。申请人打算通过实验室测量和颗粒轨迹模拟来研究浅度在流体和沉积物颗粒之间相互作用中的作用。模拟将考虑开放水域和冰覆盖的条件。研究结果将有助于制定保护汇流稳定性和底栖生态的有效策略。在通道扩张中，水流通常从其一个或两个侧壁分离。流动分离产生各种尺寸的湍流涡流。较大的涡流承载更多的能量并且能够与沉积物颗粒相互作用。其结果是在扩张范围内以及通常更下游的范围内发生冲刷、沉积和河床演化。申请人计划进行实验室实验和形态动力学模拟，以找到河道扩张冲刷问题的解决方案。申请人将使用先进的测量技术（激光多普勒风速测定法和三维粒子跟踪测速法）对瞬时流速和粒子轨迹进行可靠的测量。数字定位设备将实现精确且可重复的测量。申请人将在高性能计算集群上进行粒子跟踪模拟和高分辨率沉积物冲刷模拟。实验室测量和数学预测是相辅相成的。在加拿大，湍流引起的侵蚀在河流、溪流、排水渠和供水渠道中无处不在。这项拟议研究的结果将有助于实现两个长期目标：(a) 制定合理的分析和预测策略，以支持河流工程和水资源工程的实际和管理活动； (b) 为决策者创建可靠数据，以满足环境和经济需求。

The applicant proposes to study turbulence and its interaction with sediments in water channels. Turbulence over channel-beds causes bed-sediment scour and deposition, influencing the stability of a river channel. Channel instability has a detrimental impact on the effectiveness of river engineering schemes for flood control, navigation improvement, and the safe use of in-stream structures. The flow dynamics of the sediment-water interface region are complex and poorly understood. The objective of the proposed research is to provide an improved understanding of complex flow dynamics. In a river confluence, two streams of different flow velocities combine to form a single channel, the combining flow features velocity shear. The associated vorticity can lead to hydrodynamic instability and the development of turbulence. Turbulent eddies have the ability to scour sediment particles from the bed and sweep them downstream. Past research has focused on turbulent mixing between the incoming fluids, assuming negligible bed friction. This assumption is invalid for flows through a shallow confluence. The applicant intends to investigate the role of shallowness in the interaction between fluid- and sediment-particles by means of laboratory measurements and particle trajectory simulations. The simulations will consider both open-water and ice-covered conditions. The results will be useful for the development of effective strategies for the protection of confluence stability and benthic ecology. In a channel expansion, water flow typically separates from one or both of its sidewalls. Flow separation creates turbulent eddies of various sizes. Larger eddies bear more energy and are capable of interacting with sediment particles. The result is scour, deposition, and bed evolution within the expansion and often further downstream. The applicant plans to conduct laboratory experiments and morphodynamic simulations in order to find solutions to the problem of scour in channel expansions. The applicant will use advanced measurement techniques (laser Doppler anemometry and three-dimensional particle tracking velocimetry) to produce reliable measurements of the instantaneous flow velocity and particle trajectories. Digital positioning devices will allow accurate and repeatable measurements. The applicant will perform particle tracking simulations and high-resolution sediment scour simulations on high performance computing clusters. The laboratory measurements and the mathematical predictions are complementary to each other. In Canada, turbulence-induced erosion is omnipresent in rivers, streams, drainage canals, and water supply channels. The results from this proposed research will help achieve two long-term objectives: (a) developing sound analysis and prediction strategies to support practical and managerial activities in river engineering and water resources engineering; (b) creating reliable data for decision makers to address environmental and economic needs.