Stratified Two-Phase Turbulent Pipe Flow Simulations

Gas-liquid two-phase flows in pipes are common in various industrial processes requiring fluid transport through pipes and ducts under varying operating conditions. Computational fluid dynamics (CFD) simulations of various conditions of gas-liquid turbulent flow in a horizontal circular pipe are presented in the current paper. The simulations utilize the Level-set Method coupled with the Volume of Fluid (VOF) method to calculate the normal interface for the VOF re-construction step. In the present approach, the flow governing equations are solved numerically first for the mixture, followed by an additional equation for the second phase. A geometric re-construction technique is then used to reconstruct the interface between the two phases. This geometric re-construction technique is based on a piece-wise-linear interface construction approach. For the simulations, a number of eddy viscosity models (EVM) were tested, namely, k - ε, k - ω, and the Re-Normalisation Group (RNG) k - ε in both standard and differential form of turbulence viscosity. Numerical results were validated against detailed measurements and mechanistic models and were found to be in complete agreement. The results were analyzed for the flow physics of the transfer of momentum across the stratified two-phase using the velocity profiles of the gas and liquid phases, liquid hold-up, and different hydrodynamic forces. The paper also highlights the suitability of such a coupled VOF approach for stratified flows via comparisons against measurements and common industrial mechanistic models.