明渠凹槽泥沙回填过程的水沙两相相互作用

Interaction of water and sediment in the process of sediment backfilling in open channel grooves

航道疏浚和河流挖沙引起的深槽及深坑的泥沙回淤是典型的水沙两相运动过程。以往针对深槽及深坑的泥沙回淤数值模拟多假定泥沙速度等于水流速度,忽略了水流和泥沙之间的相互作用。通过建立平面二维水沙两相数学模型,分别求解浑水和泥沙的守恒方程,并将该模型与传统拟单相流模型对比,复演了两个典型明渠凹槽的泥沙回填水槽实验。研究发现:在同等参数条件下,水沙两相流数学模型能更好地复演实测结果。分析水沙之间相互作用发现,泥沙主要受底床切应力、水沙之间相互作用力和颗粒间作用力的影响,其中,底床切应力阻碍泥沙运动,水沙之间相互作用力是泥沙运动的主要动力来源。

The back deposition phenomenon of deep trench/pit caused by waterway dredging and river sand mining is a typical water-sand movement process. However, the previous mathematical simulations for the backfilling of deep trenches or pits assumes that the sediment phase velocity is equal to the water velocity, ignoring the interaction between the water and sediment, which brings the results uncertainty. This paper solves the conservation equations of water phase and sediment phase, and establishes the 2 D water-sediment two-phase model. Then we the above two-phase model is compared with the traditional quasi-single-phase model to study the process of backfilling of two typical open channel grooves. The result shows that the two-phase model can always reproduce the measured results better under the same parameters. Results show that the sediment phase is mainly affected by the shear stress of the bottom bed, the interaction force between water and sediment, and the force between particles. The shear stress of the bottom bed hinders the movement of the sediment phase, and the interaction force between water and sediment is the main source of power for sediment movement.