水流冲击多段滞留气团的三维数值模拟

针对水气两相瞬变现象,充分考虑了水体弹性、气体可压缩性、水-气交界面的动态运动以及多段气团间相互作用,采用三维CFD方法对起伏管道内含多段滞留气团的水气两相作用进行建模和模拟,选择Standard k-ε湍流模型进行模拟研究,将三维计算结果、现有一维模型计算结果与试验结果进行对比分析,并通过水气两相分布图展现动态变化过程.结果表明:与一维模型相比,三维CFD模型能够更为准确地模拟起伏管道内瞬变压力波动,并且能够清楚描述水气掺混、耦合的动态变化.水流冲击初始两段滞留气团压力波动曲线显示,多气团间的瞬变压力并非同步变化,可能呈现多气团峰值压力交替出现的情况,这与初始气团长度密切相关.水气交界面自由变化,阻断水体长度时刻发生变化,当水体运动到管道弯曲处时会产生新的阻断水体,将气团分成若干部分.

Three-dimensional numerical simulation of transient pipe flow with multiple entrapped air pockets

Aiming at the air-water two-phase transient flow phenomenon,the elasticity of the water,the compressibility of the gas,the dynamic motion of the water-gas interface,and the interaction between the multiple air pockets were fully considered.The three-dimensional(3D)CFD simulations was used to simulate the two-phase interaction of water and gas with multi-segment in undulating pipeline with Standard k-εturbulence model.The 3D CFD simulations result,existing one-dimensional(1D)modeling results and the experimental data were compared and analyzed,and the dynamic change process was displayed through the water and gas two-phase distribution.The results show that compared with the 1D model,the 3D CFD model can more accurately simulate transient pressures fluctuation in the undulating pipeline,and can clearly describe the dynamic behaviors of water-gas mixing and inte-raction.The pressure fluctuation curve of transient flow with initial two air pockets show that multiple air pockets have different transient pressure fluctuations,and the maximum pressures may alternately arise in two air pockets,which is closely associated to initial air length.The water-air interface changes freely,and the length of the blocking water body changes momentarily.When the water body moves to the bend of the pipeline,a new blocking water body is generated,whcih divides the air mass into several parts.