圆管有压流输沙与泥沙垂向分选特性试验研究

Study on characteristics of sediment transport and sorting in pressure pipe

管道输沙是实现黄河水沙资源重分配的有效手段之一,广泛用于水库泄洪排沙、河道疏浚及滩区淤沙等工程。以黄河流域水库高含沙隧洞和管道输沙为工程背景,设计了循环管道输沙试验系统,以d_(50)=107μm的黄河细沙为试验材料,研究有压封闭环境下不同含沙浓度引起的断面流速、泥沙浓度垂向分布等物理量的变化,并采用Malvern3000粒度分析仪对分层泥沙样品进行颗粒分析,探讨泥沙垂向分选特性。试验结果表明:泥沙的存在会改变清水流场分布,小流量工况的水动力较弱,含沙浓度的增加引起断面流速分布不对称,垂向泥沙颗粒出现明显分层;随着流量增大,流速不对称性有所降低,含沙浓度沿垂向趋近均匀分布,泥沙分选效果减弱。

Sediment transport in pipe is one of the effective engineering measures to reallocate the water-sediment resources,which is widely used in reservoir flood and sediment discharging,river dredging and floodplain area deposition,and other projects.Based on the engineering background of the hyper concentration transportation pipe in the Yellow River Basin,the circulating pipe sediment transport experimental system was designed.Fine-grained sediment of the Lower Yellow River,with a median grain size(d_(50))of 107μm,which used as the experimental materials to explore the flow velocity,concentration distribution in pressure pipe.The particle size analyses are used for sediment samples at different elevations along the vertical,and the vertical separation characteristics of sediment are discussed.Results show that the sediment laden flow changed the distribution of clean water flow field.At the small water flow rate,the increase of sediment concentration causes asymmetric distribution of cross-section velocity and obvious stratification of vertical sediment particles.with the increase of water flow rate,the asymmetry of velocity distribution was decreased,the concentration tends to be uniform distribution along the vertical direction,and the separation effect of sediment was weakened.