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

本研究的目的是弄清变流量条件下滩地植被周围水流的响应特征，研究植被和丁坝周围的中尺度非恒定流结构。采用非恒定供水系统对植物生长的两级流进行了实验研究，并采用二维平均水深数学模型进行了数值模拟。其次，对丁坝和植被带周围的非定常湍流结构进行了研究，发现了有植被和无植被的非恒定流结构之间的一些显著差异。滩地植被通过植被配置的影响，增加了主槽流速的不平稳性。洪泛区植被较短，导致其前方水流深度急剧减小，上游水位极大增加。洪水…中植被非恒定流的二维深度平均数值计算技术更多的平原被开发出来。计算结果较好地再现了实验的特征趋势。研究了不同渗透率条件下丁坝的流动特性和旋涡结构。丁坝不透水时，在丁坝后产生强环流，但在动床条件下，由于大量冲刷和淤积，这种环流减弱。折射流透水丁坝的阻力和冲刷效果较小，但其后方可形成宽阔的环流带。通过试验研究了滩地疏林林带复合明渠水流的流动和旋涡结构。在这些植被流中观察到了大尺度的周期性涡旋运动，并利用非定常平均水深二维模拟方法对其进行了再生，相信本文的研究结果将为水利工程提供有用的知识。较少

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