CFD simulation of two-phase gas/non-Newtonian shear-thinning fluid flow in pipes

The multiphase flow has always been a major concern since it is encountered in many industrial processes that are crucial. Gas/non-Newtonian two-phase flow is found in the upstream of the petroleum industry, where slug flow is the most common flow pattern. This flow pattern has complex hydrodynamics which is crucial to study and evaluate. This study assessed the two-phase gas/non-Newtonian fluid flow in different configurations of pipes. The model was developed using computational fluid dynamics with an orthogonal mesh to evaluate the behavior of the slug dynamics in the different configurations. The model volume of fluid was used to estimate and predict the most important parameters: pressure drop, slug frequency, and length. First, the model was validated with experimental data found in literature in a horizontal 9-m long glass pipe, with an inner diameter of 22.8 mm. The validation was made with carboxymethyl cellulose CMC-water solutions as test fluids. Two concentrations (w/w) of CMC were used: 1% and 6%. The overall average relative error of the model, taking into account the three parameters, was 24.9%. With this result, it was proceeded to evaluate the model and the effect in the slug flow in three different pipe trajectories: toe-down well, one undulation with a hump well and one undulation with a sump well. The comparison was made between results of a gas/Newtonian fluid flow and the gas/non-Newtonian fluid flow. It was found that the slug frequency and length vary in great form. The slug frequency increased in almost all the cases, and the slug length decreased.