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

河道中淹没植被的存在导致河道流阻增大，河道流量减小。由于这个原因，植被经常被从河床上移除。生物学家和生态学家已经认识到，水下植被可以提供广泛的重要生态系统服务。水生植物有助于降低浊度，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具有巨大的生态和经济效益。

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.