Comparison between eulerian and vof models for two-phase flow assessment in vertical pipes

Abstract

he appropriate characterization of the two-phase flow has been recently considered as a topic of interest at industrial level. The Computational Fluid Dynamics (CFD) is one of the techniques used for this analysis. Commonly, the Volume Of Fluid (VOF) model and the Eulerian model are used to model the two-phase flow. The mathematical formulations of these models cause differences in their convergence, computational time and accuracy. This article describes the differences between these two models for applications in the two-phase upward-flow. In order to accomplish this objective, the CFD models were validated with experimental results. This study modeled six experiments with an orthogonal (butterfly) grid. As a result, the Eulerian model shows mean square errors (13.86%) lower than the VOF model (19.04%) for low void fraction flows (< 0.25). Furthermore, it was demonstrated that Eulerian model performance is independent from grid, spending less computational time than the VOF model. Finally, it was determined that only the VOF model predicts the pattern flow.

Entropy and Hurst analysis for the determination of two-phase flow time series complexity

“…And the VOF multi-phase model which presents an adequate detail of the bubbles in the two phases, solves the interface by means of the continuity of the equation as a function of the volume fraction and predicts the flow pattern. (Gelves et al, 2013, Guerrero et al, 2017.…”

Nitrogen-Galinstan Two Phase Pumping for MHD Power Generation Systems

“…A two-phase Volume of Fluid (VOF) model was applied for nitrogen and user-defined galinstan in an isothermal system. This type of model was chosen based on previous studies and the capabilities to more accurately predict the two-phase flow patterns occurring in a vertical riser pipe [12]. The standard K-ε turbulence model was applied due to its ability to accurately represent a wide range of turbulent flows [13].…”

CFD study and experimental validation of low liquid-loading flow assurance in oil and gas transport: studying the effect of fluid properties and operating conditions on flow variables

“…Selecting CFD models is usually an act of balancing accuracy and efficiency. Using a single set of transport equations for all phases reduces the computational cost of the model significantly and increases its robustness and stability compared to the Eulerian Multiphase model, which models a separate transport equation for each phase (Guerrero et al, 2017). However, it may also reduce the accuracy of the model.…”

“…Considering the simplifications assumed by the VOF method, which are related to its computational efficiency, the 20% error for the liquid holdup and 12% for the pressure drop was considered acceptable. This was also based on the fact that in CFD studies, especially of multiphase flow or gas modeling, an error of up to 20% or even 30% is not unusual (Guerrero et al, 2017;Fatima and Chaudhry, 2017;Rivas et al, 2019).…”