Numerical Simulation of Flow Parameters in Stratified Gas-Liquid Flow in a Horizontal Pipe

Abstract

The transportation of gas-liquid mixtures in horizontal pipes as two-phase stratified flow is examined using computational fluid dynamics (CFD) method. The design of these pipelines requires accurate prediction of flow parameters such as pressure drop and liquid holdup. Many empirical correlations have been developed in the last 70 years and are well documented in the literature to obtain these parameters using experimental, analytical and numerical methods.

In this investigation, the numerical method based on CFD code-FLUENT is used as an alternative to the experimental method to obtained numerical data such as gas wall shear stress, liquid holdup and pressure drop in order to calculate interfacial shear stress using semi-mechanistic flow model for stratified-smooth and stratified-wavy flow based on the 3D CFD models developed in FLUENT DesignModeler. The Volume of Fluid (VOF) model and k-ω SST turbulence model were used to obtain numerical data from the CFD models for validations.

In the 3D CFD model for gas flow over stationary liquid surface, the average gas velocities and corresponding liquid heights from the experimental data were validated in the two-phase flow domain. The interfacial friction factor correlation proposed was in good agreement against the existing two-phase friction factors using conventional two-phase flow calculation method, while the mathematical formulations involving hydrostatic force for the interfacial and gas wall shear stresses were poorly correlated against existing correlations.

In the co-current gas-liquid flow 3D CFD model, the pressure drop, gas wall shear stress, interfacial shear stress and liquid holdups were in excellent agreement and the interfacial friction factor correlations proposed were in good agreement with the published correlations. The flow patterns were correctly predicted as stratified-smooth and wavy flow on the flow map.

A design procedure involving both 3D CFD models was proposed and presented in Appendix D.