明渠交汇水流阻力对平面二维数值模拟的影响

与顺直明渠水流相比,明渠交汇水流由于存在分离区和自由剪切面,其紊动特性引起的阻力较为复杂,交汇水流除床面阻力外还受到较强的阻力。基于数值模拟与实验比较分析表明,分离流与自由剪切流所产生的阻力(紊动粘性阻力)对于交汇水流数值模拟具有重要影响。同时,由于平面二维模型对二次流影响的忽略,断面环流较强时数值模拟会产生较大的阻力(环流阻力),而断面环流较弱时,交汇水流的三维特性相对较弱,采用平面二维模型和k-ε紊流模型能达到较好的模拟效果。因此,紊动及环流阻力的计算对交汇水流数值模拟的精度至关重要。

Influence of additional resistances on numerical simulation of 2D flow at river channel confluences

Due to separated flow and free shear flow,the turbulent properties at river channel confluences are much different from that in common channels.By comparing experimental data with numerical simulations,the significance of additional resistances resulting from separated flow and free shear flow is illustrated in this study.Because of the two-dimensional(2D) assumption,the vertical velocity variation is not considered in 2D models,which can result in large errors for high flow rate ratios.In contrast,the assumption is generally valid for low flow rate ratios.Thus,the proper treatment of additional resistances in numerical simulation of confluence flow is vital to the success of solving engineering problems.