Abstract：Aiming at the air-water two-phase transient flow phenomenon, the elasticity of the water body, the compressibility of the gas, the dynamic motion of the water-gas interface, and the interaction between the multiple air pockets were fully considered in this paper. The Standard k-ε turbulence model and the three-dimensional(3D)CFD simulations were used to simulate the two-phase interaction of water and gas with multi-segment in undulating pipeline. 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 interaction. 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 was 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 was ge-nerated, whcih divided the air mass into several parts.
