Three-Dimensional Simulation of Transient Flows during the Emptying of Pipes with Entrapped Air

Two- and three-dimensional analyses of transient flows considering the air–water interaction have been a challenge for researchers due to the complexity in the numerical resolution of the multiphase during emptying in pressurized water pipelines. The air–water dynamic interaction of emptying processes can be analyzed using thermodynamic and hydraulic laws. There is a lack in the current literature regarding the analysis of those phenomena using 3D models. In this research, several simulations were performed to study the complex details of two-phase flows. A 3D model was proposed to represent the emptying process in a single pipeline, considering a PVoF model and two-equation turbulence model. The model was numerically validated through 12 experimental tests and mesh sensitivity analysis. The pressure pulses of the air pockets were evaluated and compared with the experimental results and existing mathematical models, showing how the 3D models are useful for capturing more detailed information, such as pressure and velocity patterns of discrete air pockets, distribution of air and water velocity contours, and the exploration of temperature changes for an air pocket expansion.