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

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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".