Rheological Characteristics and Dynamical Mechanism in Hyperconcentrated Sediment-laden Flow

在黄河流域，高含沙洪水引起了严重的泥沙冲淤，引起了许多严重的河流问题。本文首先研究了黄河下游泥沙颗粒和高岭土颗粒充分发展的管流紊流特性。水流数据包括摩擦系数与雷诺数、体积含沙量、平均流速的关系。此外，还利用同轴圆筒流变仪和平行平板流变仪对泥石流的流变特性进行了研究。试验结果表明，在高含沙量下， ...更多信息 在低剪切速率下，Bingham模型不适用，摩擦系数随含沙量的增加而增加，这是由于粘性增加了2 ~ 3个数量级.此外，本文还利用粒子图像测速仪（PIV）研究了非牛顿流体对沙丘型固定床分离涡的影响.结果表明，与清水相比，流变特性显著地消散了沙丘床面上的湍流脉动，增大了流动阻力。最后，利用粒子图像测速仪（PIV）实验研究了非牛顿流体对砾石床面阻力特性和流动结构的影响。结果表明，高岭土掺量在8%左右时，砾石床明渠水流的流动结构发生了明显的变化，表现为阻力减小<8% and followed by a subsequent increase in the region of Cv >。少

The need to understand and predict flows that carry large suspended sediment loads has become acute in the Yellow River basin where significant erosion and siltation associated with hyperconcentrated sediment-laden flood give rise to many serious river problems. Mud flows, debris flows or slurries, made up of a large amount of clay and/or silt particles suspended in water, often show non-Newtonian properties but remain poorly understood concerning their rheological properties.First of all, this paper concerns an experimental study of the fully developed turbulent pipe flow with kaolin particles or silt particles deposited in lower region of the Yellow River Basin. The flow data include friction factor vs. Reynolds number, volumetric sediment concentration, mean flow velocity. In addition, the rheological properties of the mudflows were investigated by using both coaxial cylinder rheometer and parallel plate one. The experimental results stressed that at high sediment concentration mudf … More lows did not fit to the Bingham model at low shear rates, the friction factor increased with the sediment concentration which result from the viscosity increase by two to three orders magnitude.In addition, we experimentally investigated the effects of non-Newtonian fluid on the separation vortex over fixed dune type bed by using Particle Image Velocimetry(PIV). The results showed that rheological properties significantly dissipated the turbulent flow fluctuations over the dune bed and augmented the flow resistance by comparison with the clear water flow.Finally, we experimentally investigated the effects of non-Newtonian fluid on resistance characteristics and flow structure over gravel bed by using Particle Image Velocimetry (PIV). The results showed that Kaolin water mixtures in gravel bed open channel flows considerably changed flow structures and took the form of resistance decrease with Kaolin fraction Cv in the region of Cv <8% and followed by a subsequent increase in the region of Cv >8%. Less