On Multiphase Flow Models in ANSYS CFD Software

Multiphase flow is a common phenomenon in many industrial processes, amongst them the oil and gas industry. Due to the complexity of multiphase flow, development of reliable analysis tool is difficult. Computational fluid dynamics (CFD) has been an established tool for flow analysis in the field of single phase flow for more than 20 years but has only started to become established in the multiphase field as well. To be able to use CFD in a meaningful way it is important to investigate, understand and validate the many models offered in commercial codes. The purpose of this thesis is to compare multiphase models available in the ANSYS software Fluent and CFX and perform simulations using the different models. The simulations were based on an experimental study concerning air-water mixtures in a vertical T-junction with horizontal branch. When a gas-liquid mixture flows into a branching pipe junction phase redistribution will occur and a higher proportion of gas will enter the side branch. The aim of the simulations was to find models/settings that accurately predict the phase redistribution phenomenon and investigate the effect of changing simulation parameters. This was done by systematically changing parameters and validating the results against the experimental data. Based on the simulations, it was evident that the Euler-Euler modelling approach was best suited for predicting the phase redistribution phenomenon in the T-junction. The choice of dispersed phase diameter was found to have the largest effect on the results. Generally, the predicted average volume fraction in each arm was in quite good consistency with experimental data while the predicted velocities were in low agreement. However, adding models to account for polydispersed flow increased the agreement also for the velocity