TURBULENT FLOW AND TRANSPORT IN OPEN CHANNELS WITH NATURAL ROUGHNESSES: EXPERIMENTS AND NUMERICAL SIMULATIONS

输水渠道中沉水植被的存在，导致水流阻力增大，渠道通过能力降低。出于这个原因，河床上的植被经常被移走。生物学家和生态学家已经认识到，沉水植被可以提供广泛的重要生态系统服务。水生植物有助于减少浑浊、去除营养物质、产生氧气和改变沉积物的运输。研究湍流与水生植被的相互作用及其在养分循环、控制侵蚀和保护河岸方面的作用，可以产生巨大的生态和经济效益。 流体与植物的相互作用可能是相当复杂的。水生植物及其产生的剪切层可以占据整个流动领域的很大一部分。沉水植物可以是柔性的，将流体和树冠的运动耦合在一起。除了浮力外，灵活的天篷还可以随着水流表现出连贯的波动。由于茎的刚性，植被的形态也可以在姿势中发挥重要作用，这可以影响阻力。阀杆刚度、叶片形状、位置以及它们与流动的相互作用的综合影响仍不清楚。对灵活的水生植物的阻力的普遍描述仍然难以捉摸。目前的研究计划是朝着更好地理解明渠中沉水植被和湍流之间的相互作用迈出的一步。主要目标包括：(1)通过实验和数值模拟研究与柔性和刚性植被相关的流动、湍流和输运的主要特征；(2)对柔性植被的阻力进行量化，这对于理解流体-植物相互作用至关重要。(3)有限块柔性和刚性植被的流体动力学；(4)斑块尾迹中的湍流和相干结构的研究。 除了培训HQP和影响政策制定者外，拟议的研究还将对其他温莎研究项目产生积极影响，因为为该项目组装的数值和实验工具可以成功地应用于其他调查。

The presence of submerged vegetation in conveyance channels leads to an increase in flow resistance and reduction of channel flow capacity. For this reason, vegetation has often been removed from channel beds. Biologists and ecologists have recognized that submerged vegetation can provide a wide range of important ecosystem services. Aquatic vegetation helps reduce turbidity, remove nutrients, produce oxygen and alter sediment transport. Studying the interaction of turbulence with aquatic vegetation and its role in cycling nutrients, controlling erosion, and protecting riverbanks can have enormous ecologic and economic benefits. The fluid flow-plant interaction can be quite complex. Aquatic plants and the shear-layers that they generate can occupy a significant fraction of the total flow domain. The submerged plants can be flexible, coupling the motion of the fluid and the canopy. Besides being buoyant, flexible canopies can exhibit a coherent waving in response to the flow. The morphology of the vegetation can also play an important role in the posture due to the stem stiffness, which can influence the drag. A combined effect of stem stiffness, blade shape, positioning and their interaction with the flow is still not well understood. A universal description of drag for flexible aquatic vegetation remains elusive. The present research program is a step towards better understanding of the interaction of clusters of submerged vegetation and turbulence in open channels. The major goals include: (1) To study the major features of flow, turbulence and transport associated with flexible and rigid vegetation via experiments and numerical simulations and (2) To quantify the drag in the case of flexible vegetation that appear vital for understanding the fluid-plant interaction. (3) The fluid dynamics of finite patches of flexible and rigid vegetation and (4) Investigation of turbulence and coherent structures in the wake of the patch. Besides training HQP and influencing policy makers, the proposed research will also have a positive influence on other Windsor research programs as the numerical and experimental tools assembled for this project can be successfully employed in other investigations.