STUDY ON UNSTEADY RESPONSE CHARACTERISTICS OF FLOW AROUND HYDRAULIC STRUCTURES ENVIRONMENTALLY CONSIDERED

本研究的目的是阐明变流量条件下滩地植被绕流的响应特征，并探讨中尺度非恒定流中植被和丁坝绕流结构。本文采用非恒定供水系统对植生两相流进行了试验研究，并采用二维水深平均数学模型进行了数值模拟。其次，研究了丁坝及植被覆盖区的非恒定流结构，揭示了有无植被覆盖区的非恒定流结构的一些显著差异。河漫滩的植被通过植被配置的作用，增加了主槽流速的不稳定性。河漫滩中的短植被带导致其前方的水流深度急剧减小，并极大地增加了上游水位。有植被的洪水非恒定流二维水深平均数值计算技术 ...更多信息 平原是发达的。计算结果很好地再现了实验的特征趋势。该计算方法可用于通过这种复杂流场的洪水演进。研究了不同渗透率丁坝周围的水流特性和旋涡结构。丁坝不透水时，丁坝后产生较强的环流，但在动床条件下，由于大量冲淤，环流减弱。透水丁坝折射流的阻力和冲刷作用较小，但可在坝后形成较宽的环流区，本文对滩地疏林和密林复合明渠水流的水流和涡结构进行了试验研究。研究结果表明，在植被覆盖的水流中，可以观察到大尺度的周期性旋涡运动，并可以通过二维非定常水深平均数值模拟再现，为水利工程设计提供了有益的参考。少

The purpose of this study is to clarify the response characteristics of the flow around the vegetation on the flood plains under changing discharge and to investigate the middle-scale unsteady flow structures around the vegetation and the spur dikes. The study on vegetated two-stage flow was conducted experimentally by using unsteady water supply system and numerically by using 2-D depth averaged mathematical model. Next, unsteady turbulent flow structures around the spur dikes and vegetated zone were investigated.Some noticeable differences between unsteady flow structures with and without vegetation were revealed. The vegetation in the flood plains increases the unsteadiness of the main-channel velocity by the effects of vegetation arrangement. The shortly vegetated zone in the flood plains causes a sharp decrease of the flow depth in front of that and increases an upstream stage extremely. 2-D depth-averaged numerical calculation technique for unsteady flow with vegetation in flood … More plains was developed. The calculated results reproduce well the characteristic tendency of the experiments. This calculation method is useful for the flood routing passing such a complex flow field.The nature of flow and vortex structure around the spur dikes with various permeability were investigated. 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. The permeable spur dike with refracted flow has mild effects for resistance and scouring but can make broad circulation zone behind it. The flow and vortex structures are studied experimentally in compound open channel flows with loosely and densely wooded zone on flood plains. 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 hydraulic engineering. Less