• CFD
• drag-reducing polymers
• gas-liquid flow
• multiphase flow
• turbulent pipe flow

The injection of small amount of high molecular weight long-chain polymers into turbulent flows could decrease the pressure drop in the pipe flow and consequently decrease the required pumping power. This work is aimed to the modeling of viscoelastic fluid, specifically polymer, in single phase and 2-phase flows.
A literature review of drag-reduction by polymers in multiphase flow is firstly presented, then two different approaches are analyzed: one-dimensional analytical approach and CFD approach. Stratified gas-liquid flow and gas-liquid slug flow regimes are analyzed by means of analytical models developed by Taitel and Dukler (1976) and Taitel and Barnea (1990), respectively. The models are adapted for polymer solutions in order to estimate the pressure gradient and the holdup.
For single-phase flow, the modified k-ε model for power-law fluids developed by Ro and Ryou (2012) was implemented in Fluent through a User Defined Function (UDF) and validated for two polymer solutions CarboxyMethyl Cellulose (CMC) and Xanthan Gum (XG) in a turbulent pipe flow. The applicability and the effect on the structure of the flow of the modified k-ε model were studied for stratified and slug flow using the ANSYS Fluent software package.