Turbulent Flow Structure and Flow Resistance of Hyper-concentratedSediment Laden Flow with Artificial Roughness

本文研究了规则排列的方形粗糙度对带有均匀不锈钢方肋的全粗糙床的流动阻力和湍流特性的影响。在沿着完全粗糙的床面的垂直平面上，利用粒子图像测速仪（PIV）对流向和垂向速度脉动进行了详细的空间测量。实验结果表明，三维方形粗糙度的流动阻力大于二维方形粗糙度，最大值出现在横向间距δ/k处（横向间距/粗糙度高度比）=1时，沿粗糙单元产生了明显的时均速度空间规律性变化。由大量悬浮在水中的粘土和/或淤泥颗粒组成，通常表现出非牛顿特性，但关于其流变特性对充分发展的湍流结构的影响仍然知之甚少。本文利用粒子图像测速技术（PIV）对二维方肋明渠高含沙水流的阻力和动量输移进行了实验研究。结果表明，与清水相比，流变特性显著地消除了沙丘床面上的湍流脉动，增大了流动阻力

Effects of regularly arrayed square roughness on flow resistanceand turbulent characteristics in an open channel have been investigated over a completelyrough-bed with uniform stainless square ribs. Detailed spatial measurements of streamwiseand vertical velocity fluctuations were conducted using Particle Image Velocimetry (PIV)in a vertical plane along the completely rough bed surface. Experimental results indicatedthat flow resistance with three-dimensional square roughness is higher than that withtwo-dimensional square roughness, the maximum value of flow resistance appeared intransverse spacingδ/ｋ （transverse spacing/roughness height ratio）=1 and significantdegrees of spatially regular variation in the time-averaged velocities were generatedalong the rough elements.Mud flows, debris flows or slurries, made up of a large amountof clay and/or silt particles suspended in water, often show non-Newtonian propertiesbut remain poorly understood concerning the impacts of their rheological properties onfully developed turbulent structure. In this study, we experimentally investigatedresistance and momentum transport of hyper- concentrated sediment laden-flow in an openchannel with two-dimensional square ribs by using Particle Image Velocimetry(PIV). Theresults showed that rheological properties significantly dissipated the turbulent flowfluctuations over the dune bed and augmented the flow resistance by comparison with theclear water flow