A Comparison of VOF and Euler-Euler Approaches in CFD Modelling of Two-Phase Flows With a Sharp Interface

2020 ◽  
Author(s):  
Luc Bertolotti ◽  
Richard Jefferson-Loveday ◽  
Stephen Ambrose ◽  
Evgenia Korsukova
Keyword(s):  
Shear Flows ◽  
Two Phase Flow ◽  
Thickness Distribution ◽  
Volume Of Fluid ◽  
Sharp Interface ◽  
Experimental Measurements ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase ◽  
Two Phases

Abstract In aero-engines, it is important to predict the behavior of shear flows in the different parts such as bearing chambers or gearboxes. In bearing chambers, the thickness distribution of wavy films is well studied as two-phase flows are still very hard to predict depending on the case. Experimental studies remain very expensive to carry out and Computational Fluid Dynamics (CFD) still struggles with two-phase flow prediction especially when a sharp interface between the two phases must be modelled. CFD is used to predict the oil film thickness distribution and interface velocity at different engine operating conditions. Currently Reynold-Averaged Navier-Stokes (RANS) CFD uses a semi-empirical method of turbulence damping, which is inaccurate for wavy films and so impacts the modelling of bearing chambers and gearboxes. With the objective of improving RANS models from Large Eddy Simulation (LES) methods, the Volume of Fluid (VOF) and Euler-Euler methods for two-phase flow modelling are investigated in this study. The Volume of Fluid (VOF) approach assumes a single set of momentum equations for the two phases and volume fractions are 1 or 0 everywhere except in the interface region. An alternative to VOF, is the Euler-Euler method with interface sharpening for shear flows. This approach assumes one set of momentum equations per phase but a shared field of pressure. The VOF and Euler-Euler approaches are compared in this study using LES with the CFD code OpenFOAM v6. The case study is based on experimental work investigating stratified flow in a horizontal channel that will be further detailed in the paper. In this study, a simplified 3D periodic channel filled with two distinct phases: air and water is used. A flow regime is studied in which flows are fully developed and the water phase has a much smaller velocity than the air phase in order to obtain a shear flow. Numerical results are compared with experimental measurements from the literature. With OpenFOAM, the VOF solver used for the study is interFoam and the Euler-Euler solver used is reacting-MultiphaseEulerFoam. Velocity profiles, shear-stress profiles and kinetic energy profiles are compared with experimental measurements for the assessment of the two flow solvers. Maps of vorticity magnitude are also provided to support the comparisons between the Euler-Euler and the VOF approaches as well as an appropriate vortex identification method.

A Comparison of VOF and Euler-Euler Approaches in CFD Modelling of Two-Phase Flows With a Sharp Interface

2021 ◽  
pp. 1-30
Author(s):  
Luc Bertolotti ◽  
Richard J Jefferson-Loveday ◽  
Stephen Ambrose ◽  
Evgenia Korsukova
Keyword(s):  
Two Phase Flow ◽  
Thickness Distribution ◽  
Empirical Method ◽  
Sharp Interface ◽  
Navier Stokes ◽  
Computational Time ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Cfd Modelling ◽  
Two Phase

Abstract In aero-engines, predicting the behavior of shear flows in bearing chambers and gearboxes is of great importance. The thickness distribution of wavy films is well studied in bearing chambers as two-phase flows are still very hard to predict depending on the case. Experiments remain very expensive to carry out and Computational Fluid Dynamics (CFD) still struggles with two-phase flow prediction especially when a sharp interface between the phases must be modelled. CFD is used to predict the oil film thickness distribution and current Reynold-Averaged Navier-Stokes (RANS) CFD uses a semi-empirical method of turbulence damping, which is inaccurate for wavy films and so impacts the modelling of bearing chambers and gearboxes. With the objective of improving RANS models from Large Eddy Simulation (LES), the Volume of Fluid (VOF) and Euler-Euler methods for two-phase flow are investigated in this study using an artificial sharpening method of the interface. Based on existing experiments from the literature a 3D periodic channel filled with air and water is used. The air velocity is greater than the water velocity in order to create a shear flow. The LES results are compared with the experiments to determine which multiphase method gives the best results using velocity, Reynolds stress and turbulent kinetic energy profiles. Maps of vorticity magnitude and Q-criterion isosurfaces are provided to support the comparison. The two methods gave approximately the same results even though the VOF method has by far the smallest computational time.

Numerical Investigation of Countercurrent Two-Phase Flows Using Three-Dimensional Volume-of-Fluid Simulations

2011 ◽  
Author(s):  
Gae¨l Gue´don ◽  
Emanuela Colombo ◽  
Fabio Inzoli
Keyword(s):  
Two Phase Flow ◽  
Three Dimensional ◽  
Volume Of Fluid ◽  
Immiscible Fluids ◽  
Vof Method ◽  
Operating Conditions ◽  
Bubble Columns ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase

Several engineering plants and components, such as nuclear reactors, boilers, bubble columns, chemical reactors or oil/gas wells may be characterized by two-phase flows. Appropriate and safe operation of these systems may be supported by the accurate prediction of the multiphase flow pattern with consistent estimation of the void fraction and flooding phenomenon. A preliminary approach for modeling flow patterns in countercurrent two-phase flows in vertical systems, based on the volume-of-fluid (VOF) method, is here presented. The general objective of the study is to investigate the feasibility of large scale two-phase systems simulations using the VOF method. The specific objective is to provide a first set of qualitative information about the fluid dynamics structures in this flow at specific operating conditions. Three-dimensional simulations are performed using a finite volume commercial CFD code. Validation of the numerical approach is achieved with experimental data taken from literature for typical air-water flows in bubble columns. The interaction of the downward water recirculation with the bubbles of air is indeed representative of a bubbly countercurrent two-phase flow and therefore may be a valuable test case. The use of the VOF method is here privileged, since no further closure relations are needed for exchange coefficients between the continuous and dispersed phases, and for breakup and coalescence of bubbles/drops. The validated model is therefore most likely applicable in complex situations where the flow behavior is unknown. Finally a specific analysis of a countercurrent two-phase flow is presented with the objective of simulating the flow within an industrial pipe where two immiscible fluids, with different density are injected. A fluid “A” is injected at the bottom of the pipe and it is supposed to exit the pipe in the upper part. A fluid “B”, immiscible in “A”, is injected at the top of the pipe in countercurrent and it is supposed not to influence the path of fluid “A” from inlet to the exit. Fluid “B” may be used for reacting somehow with fluid “A”, but in this paper only the fluid dynamic condition is considered.

Prediction of Pump Performance Under Air-Water Two-Phase Flow Based on a Bubbly Flow Model

1993 ◽  
Vol 115 (4) ◽  
pp. 781-783 ◽  
Author(s):  
Kiyoshi Minemura ◽  
Tomomi Uchiyama
Keyword(s):  
Two Phase Flow ◽  
Bubbly Flow ◽  
Phase Flow ◽  
Centrifugal Pumps ◽  
Flow Conditions ◽  
Two Phase ◽  
Performance Change ◽  
Void Fractions ◽  
Two Phases

This paper is concerned with the determination of the performance change in centrifugal pumps operating under two-phase flow conditions using the velocities and void fractions calculated under the assumption of an inviscid bubbly flow with slippage between the two phases. The estimated changes in the theoretical head are confirmed with experiments within the range of bubbly flow regime.

A Combined Eulerian and Lagrangian Method for Prediction of Evaporating Sprays

2002 ◽  
Vol 124 (3) ◽  
pp. 481-488 ◽  
Author(s):  
M. Burger ◽  
G. Klose ◽  
G. Rottenkolber ◽  
R. Schmehl ◽  
D. Giebert ◽  
...  
Keyword(s):  
Two Phase Flow ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Lagrangian Method ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase ◽  
Lagrangian Methods ◽  
Eulerian Method ◽  
Lagrangian Modeling

Polydisperse sprays in complex three-dimensional flow systems are important in many technical applications. Numerical descriptions of sprays are used to achieve a fast and accurate prediction of complex two-phase flows. The Eulerian and Lagrangian methods are two essentially different approaches for the modeling of disperse two-phase flows. Both methods have been implemented into the same computational fluid dynamics package which is based on a three-dimensional body-fitted finite volume method. Considering sprays represented by a small number of droplet starting conditions, the Eulerian method is clearly superior in terms of computational efficiency. However, with respect to complex polydisperse sprays, the Lagrangian technique gives a higher accuracy. In addition, Lagrangian modeling of secondary effects such as spray-wall interaction enhances the physical description of the two-phase flow. Therefore, in the present approach the Eulerian and the Lagrangian methods have been combined in a hybrid method. The Eulerian method is used to determine a preliminary solution of the two-phase flow field. Subsequently, the Lagrangian method is employed to improve the accuracy of the first solution using detailed sets of initial conditions. Consequently, this combined approach improves the overall convergence behavior of the simulation. In the final section, the advantages of each method are discussed when predicting an evaporating spray in an intake manifold of an internal combustion engine.

NUMERICAL SOLUTION FOR HYPERBOLIC CONSERVATIVE TWO-PHASE FLOW EQUATIONS

2007 ◽  
Vol 04 (02) ◽  
pp. 299-333 ◽  
Author(s):  
D. ZEIDAN ◽  
A. SLAOUTI ◽  
E. ROMENSKI ◽  
E. F. TORO
Keyword(s):  
Numerical Solution ◽  
Riemann Problem ◽  
Two Phase Flow ◽  
Numerical Dissipation ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Equations ◽  
Flow Problems ◽  
Slope Limiter ◽  
Two Phases

We outline an approximate solution for the numerical simulation of two-phase fluid flows with a relative velocity between the two phases. A unified two-phase flow model is proposed for the description of the gas–liquid processes which leads to a system of hyperbolic differential equations in a conservative form. A numerical algorithm based on a splitting approach for the numerical solution of the model is proposed. The associated Riemann problem is solved numerically using Godunov methods of centered-type. Results show the importance of the Riemann problem and of centered schemes in the solution of the two-phase flow problems. In particular, it is demonstrated that the Slope Limiter Centered (SLIC) scheme gives a low numerical dissipation at the contact discontinuities, which makes it suitable for simulations of practical two-phase flow processes.

Experimental Investigation on Flow Patterns and Frictional Pressure Drop of Downward Air-Water Two-Phase Flow in Vertical Pipes

2013 ◽  
Author(s):  
Yuqing Xue ◽  
Huixiong Li ◽  
Tianyou Sheng ◽  
Changjiang Liao
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Oil Recovery ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Vertical Pipe ◽  
Two Phase Flows ◽  
Two Phase ◽  
Frictional Pressure Drop

A large amount of air need be transported into the reservoir in the deep stratum to supply oxygen to some microbes in Microbial Enhanced Oil Recovery (MEOR). Air-water two-phase flows downward along vertical pipeline during the air transportation. Base on the experiment data described in this paper, the characteristics of air-water two phase flow patterns were investigated. The flow pattern map of air-water two phase flows in the pipe with inner diameter of 65 mm was drawn, criterions of flow pattern transition were discussed, and the dynamic signals of the pressure and the differential pressure of the two phase flow were recorded to characterize the three basic flow regimes indirectly. The frictional pressure drop of downward flow in vertical pipe must not be disregarded contrast with upward two phase flow in the vertical pipe because the buoyancy must be overcame when the gas flows downward along pipe, and there would be a maximum value of frictional when the flow pattern translated from slug flow to churn flow.

Sign in / Sign up

Export Citation Format

Share Document