Modeling of Water Pipeline Filling Events Accounting for Air Phase Interactions

In order to avoid operational issues related to entrapped air in water transmission mains, water refilling procedures are often performed carefully to ensure no pockets remain in the conduits. Numerical models may be a useful tool to simulate filling events and assess whether air pockets are adequately ventilated. However, this flow simulation is not straightforward mainly because of the transition between free surface and pressurized flow regimes and the air pressurization that develops during the filling event. This paper presents a numerical and experimental investigation on the filling of water mains considering air pressurization aiming toward the development of a modeling framework. Two modeling alternatives to simulate the air phase were implemented, either assuming uniform air pressure in the air pocket or applying the Euler equations for discretized air phase calculations. Results compare fairly well to experimental data collected during this investigation and to an actual pipeline filling event.