Computational fluid dynamics has been used as a tool to simulate multiphase fluids in pressurized pipelines. This tool has been limited for the simulation of experimental-scale processes by different authors to understand transient phenomena in pipes with pressurized flow with entrapped air. Today, few CFD models have been used in the industrial sector and in research for hydraulic operations in large-scale pressurized pipelines with entrapped air, since there are some gaps in the pursuit of an adequate protocol for the simulation of hydraulic processes in pressurized pipelines from an industrial approach and cases that can be used to test CFD modelling.

This study shows the use of a two-dimensional CFD model to understand the filling processes of a large-scale pipeline, taking hydraulic conduction in Valencia, Spain, which has a length of 485 m and an air valve, as a case study. This CFD model is performed using a VoF method for air and water. The model is also calibrated by means of mesh quality analysis, according to some hydraulic modelling protocols stipulated by some expert researchers in hydraulic infrastructure simulation, and subsequently validated with pressure and velocity measurements. This CFD model shows relevant information on the processes of interaction between air and water, allowing pressurized flow conditions, and free flow in some sections of the pipeline, as well as air expulsion processes through the air valve, to be identified.

The study contributes to the foundation of the hydraulic modeling of large-scale networks using CFD tools, allowing the visualization of air--water interactions, which is difficult to analyze in existing or planned pipeline infrastructures, as well as the identification of new insights that can improve the design and operational strategies of large-scale pipeline infrastructures.