Exploring turbulence-sediment dynamics for river erosion control

申请人建议研究湍流及其与水道中沉积物的相互作用。河床上的湍动会引起河床泥沙的冲淤，影响河道的稳定性。河道不稳定对河流工程方案的防洪、通航改善和河流内建筑物的安全使用的有效性有不利影响。沉积物-水界面区的流动动力学是复杂的，人们对其知之甚少。这项研究的目的是为了更好地理解复杂的流动动力学。在河流交汇处，两条流速不同的溪流汇合成一条河道，合流具有速度切变的特点。伴随的涡量会导致流体动力不稳定和湍流的发展。湍涡有能力冲刷河床上的泥沙颗粒，并将它们向下游扫去。过去的研究主要集中在进入的流体之间的湍流混合，假设床面摩擦可以忽略不计。这一假设对浅水汇流是无效的。申请人打算通过实验室测量和颗粒轨迹模拟，研究浅度在流体和沉积物颗粒之间相互作用中的作用。模拟将同时考虑开阔水域和冰盖条件。研究结果将有助于制定保护汇流稳定性和底栖生物生态的有效战略。在渠道扩展中，水流通常从其一个或两个侧壁分离。流动分离会产生各种大小的湍流旋涡。较大的涡流承载更多的能量，并能够与沉积物颗粒相互作用。其结果是冲刷、淤积和河床演变在扩张内，往往是更下游。申请人计划进行实验室试验和地貌动力学模拟，以找到解决渠道扩张中冲刷问题的方法。申请者将使用先进的测量技术(激光多普勒测速和三维粒子跟踪测速)来产生瞬时流动速度和粒子轨迹的可靠测量。数字定位设备将允许准确和可重复的测量。申请者将在高性能计算集群上进行粒子跟踪模拟和高分辨率泥沙冲刷模拟。实验室测量和数学预测是相辅相成的。在加拿大，由湍流引起的侵蚀在河流、小溪、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战略，以支持河流工程和水资源工程方面的实际和管理活动；(B)为决策者提供可靠的数据，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.