Hydraulic structures such as "Wando" and the associated Turbulent structure

本研究的目的是获得人工滨岸沼泽（“莞岛”）设计的技术指导，以创造一个自然丰富的河流环境。“莞岛”的功能是截流、沉淀悬浮物、维持水质和抗洪稳定。研究课题是厘清和控制直堤周围的湍流结构，厘清主流与植被流的混合机制。实验研究了不同渗透率直堤周围的流动性质和湍流结构。动量交换的过程在岩脉渗透率方面是不同的。在非渗透条件下，在非渗透条件下会产生较强的循环作用，但在动床条件下，由于大量冲刷和沉积，循环作用减弱。当渗透率较小时，会产生二次流，二次流在混合过程中起重要作用。在沉水直堤中，混合在灰分距离内完成，但在较长的范围内，流向速度的横向差异没有减小。透水直堤具有折射流，其阻冲作用较弱，但其背后可形成较宽的循环带。其次，研究了河岸植被对河流流量的影响。对洪泛平原松林带和密林带复合明渠流的流动和涡结构进行了实验研究。树内流动与周围流动的相互作用产生了具有特征的三维流动结构。在这些植被流动中观测到大尺度的周期性涡运动，并可以通过非定常深度平均二维模拟来再现。我们相信本研究的结果为人工“莞”的设计提供了有用的知识。

The purpose of this study is to obtain technological guides to design the artificial shore swamp ("Wando") in order to make a nature abundant river environment. The functions expected to the "Wando" are the stagnation of flow, the deposition of suspended sediment, the maintenance of water quality and the stability against flood. The study subject is to clarify and control the turbulent structure around the spur dikes and to clarify the mixing mechanism between the main flow and the vegetated flow. The nature of flow and turbulent structure around the spur dikes with various permeability were investigated experimentally. The processes of momentum exchange are different from each other with respect to the permeability of the spur dike. When spur dike is non-permeable, a strong circulation is generated behind the spur dike, but it diminishes in the movable-bed condition, because of massive scour and deposition. When the permeability is relatively small, the secondary flow is generated and plays an important role on the mixing process. In the submerged spur dike, the mixing completed in ash ort distance but the lateral difference of the streamwise velocity is not reduced for a long reach. The permeable spur dike with refracted flow has mild effects for resistance and scouring but can make broad circulation zone behind it.Next, the effects of vegetation along riverbank on the flow were investigated. The flow and vortex structures are studied experimentally in compound open channel flows with loosely and densely wooded zone on flood plains. The interaction between the flow in trees and ambient flow generates characteristic 3-D flow structures. The large-scale periodic vortex motion was observed in these vegetated flows and it could be regenerated by using the unsteady depth-averaged 2-D simulation. We believe that the results of this study give useful knowledge for designing artificial "Wando".