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为了解决明渠水流交汇口河道冲刷、泥沙沉淤、污染物滞留等问题,必须探明其水力特性的分布规律.采用气液两相流混合模型,对不同汇流比下90°明渠交汇口三维水力特性进行数值模拟研究.分别选取大涡模拟模型(LES)和RNGk-ε模型封闭两相流时均方程,速度与压力耦合方程组求解时使用半隐式SIMPLE(Semi-Implicit Method for Pressure-Linked Equations)算法,模拟自由水面采用VOF(Volume of Fluid)法.将汇流比为0.25时两种模型计算的纵向截面水面线与实验结果相比较,得出大涡模型结合VOF法能更好地捕捉交汇口水面的波动情况;将大涡模型计算的不同垂直线上的速度分布与实验结果相比较,两者吻合良好.通过比较两种模型计算的特征横断面上的流线图,得出大涡模型能更好地捕获水流瞬时流动特性,动态再现二次流动结构,且大涡模型能够更好地模拟交汇口附近水力特性分布规律.
In order to solve the problems such as river scour, sedimentation and pollutant retention at the confluence point of open channel flow, the distribution of hydraulic characteristics must be verified. By using the mixed model of gas-liquid two-phase flow, (LES) and RNGk-ε model are used to simulate the two-phase flow when both the mean equation and the coupled equations of velocity and pressure are solved by Semi-Implicit Method for Pressure- Linked Equations algorithm was used to simulate the free water surface using the VOF method.When the confluence ratio was 0.25, the longitudinal cross-section surface waterlines calculated by the two models were compared with the experimental results, And capture the fluctuation of water surface at the junction.Comparing the velocity distribution on different vertical lines calculated by large eddy model with the experimental results, the two agree well with each other.Through comparing the flow pattern on the characteristic cross-section calculated by the two models, Large eddy model can better capture the instantaneous flow characteristics of water flow, dynamically reproduce the secondary flow structure, and large eddy model can better simulate the distribution of hydraulic characteristics near the intersection.