泥石流内部流速分布规律试验研究

Experimental Investigation on the Inner Distribution of Debris Flow Velocity

泥石流内部速度是泥石流动力学分析与防治工程设计中最重要的参数之一。以黏度较高的丙烯酸树脂与乙酸乙脂混合液模拟泥石流的黏性,以粒径均匀的玻璃微珠作为两相流的固相颗粒,利用PIV流场测量系统,研究了含砂水流与泥石流中颗粒运动过程、垂向流速的分布规律;借助高桥堡水石流固体颗粒流速分布模型,计算了不同颗粒粒径条件下泥石流垂向流速分布,并与前人研究成果进行比较。结果表明:流体黏性较高条件下,颗粒在整个过流断面上分布更均匀,试验中垂向流速测量结果与高桥堡模型计算值吻合良好(u/us>0.3),而与含砂水流条件下的测量结果差异明显;两相流中固体颗粒垂线流速分布是否存在反"S"曲线分布,主要与流体的黏性及颗粒在液相中分布的均匀程度有关。

Velocity in debris flow is one of the most important parameters for dynamic analysis and design of debris flow control works. In order to investigate the velocity profile along flow depth for particle phase and liquid phase in debris flows,the mixture of two organic liquids of Acrylic acid Polymers and ethyl acetate was used to monitor the high viscosity of debris flow. The glass beads with uniform particle size were used as solid phase in debris flows. Both particle and liquid velocity components were investigated by particle image velocimetry（ PIV） measurement system under the condition of sediment flows and debris flows,respectively. The Takahashi model for the particle velocity distribution in debris flows was employed to calibrate the experimental results obtained by former researchers and measured by PIV measurement system in the experiments. The results indicated that the mixture liquid with higher viscosity produces a more uniform distribution of the particles along the flow depth. The experimental data measured by PIV system are in good agreement with the ones calculated by Takahashi model in debris flows（ u / us 〉0. 3）. However,the data did not match the formers＇ ones in sediment flows,which indicated that the shape of particle velocity profile along flow depth is mainly determined by the fluid viscosity and the uniformity of particles distributed in the flows.