等宽明渠交汇口壅水特性数值模拟

为研究不同交汇角度θ和流量比q对明渠交汇口壅水特性的影响规律，利用体积函数法(VOF)追踪自由表面，采用雷诺应力模型(RSM)封闭控制方程，建立明渠交汇水流三维数值仿真模型，对3种流量比和7种交汇角的21种组合工况进行模拟研究，对交汇口附近的三维壅水形态进行分析。结果表明:由于支流汇入的顶托作用，上游区域内水位壅高，交汇区域内出现水面跌落现象；同一流量比工况下，随着交汇角的增大，上游水位逐渐增大，下游水面跌落现象越来越剧烈；对所有工况的上下游最小水深比h^*_d和最大水深比h^*_m进行计算，发现在本文研究的流量比及交汇角变化范围内，上下游最小和最大水深比均随着交汇角的增大而增大，随着流量比的增加而减小。最后，对上下游水深比的变化范围进行分析，得出结论:同一流量比工况下，交汇角增大，交汇口附近水面变幅增大；同一交汇角度工况下，流量比增大，交汇口附近水面变幅减小。

Numerical simulation of backwater characteristics at equal-width open-channel confluences

In order to study the impact of different junction angles and discharge ratios on the backwater characteristics at open-channel confluences, a three-dimensional numerical model was established by using the Volume of Fluid(VOF)method for the free surface capture and adopting the Reynolds Stress Model(RSM)for the governing equations closure. The 3D pattern of backwater was analyzed after the simulations of 21 combined conditions for 3 different discharge ratios and 7 different junction angles. The results indicate the raising of water level in the upstream area and the dropping of water level in the junction area because of the tributary convergence. Under a same discharge ratio, the upstream water level increases as the junction angle increases, and the drop of the water surface in the downstream becomes more obvious. The minimum and maximum ratios of the upstream water depth to downstream water depth were calculated, which indicate that both the minimum and maximum depth ratios increase with a greater junction angle or a smaller discharge ratio among the ranges of junction angle and discharge ratio in the current study. The variation range of the depth ratio was also analyzed. Under a same discharge ratio, a greater junction angle leads to a larger variation range of water level around the junction area. Under a same junction angle, a greater discharge ratio leads to a smaller variation range of water level around the junction area.