Application of the one-dimensional drift-flux model for numerical simulation of gas–liquid isothermal flows in vertical pipes: a mechanistic approach based on the flow pattern

The multiphase flow prediction becomes necessary for the technical–economical feasibility of several transportation processes in the petroleum industry, among others. Depending on the flow rates, phases’ physical properties, and pipe characteristics, gas–liquid flows can assume three flow patterns: dispersed, separated, and intermittent. The drift-flux model is adopted in various commercial simulators and allows all flow patterns simulation provided that the constitutive equations are suitable for each flow pattern. The interfacial terms, the well-posedness, and the reduced number of transport equations are the main advantages of the drift-flux model in comparison with other models, such as the two-fluid model. But the constitutive laws for predicting the wall shear force are its weak point and depend on the arrangement of each flow pattern, unlike relative motion that can be determined by correlations that are flow pattern-independent or not. This work aims to perform the steady-state numerical simulation of gas–liquid flows in vertical pipes, applying a one-dimensional mechanistic approach dependent on the flow pattern, for the closing of the constitutive equations, solved in a single running algorithm. The results obtained by this approach are compared against two sets of experimental data for the pressure gradient of upward air–water vertical isothermal flow cases, presenting satisfactory results, thus demonstrating the accuracy of the approach employed.