Implementation of Two-Fluid Model for Dilute Gas-Solid Flow in Pipes With Rough Walls

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Ashraf Uz Zaman ◽  
Donald John Bergstrom
Keyword(s):  
Surface Roughness ◽  
Gas Phase ◽  
Numerical Study ◽  
Fluid Model ◽  
Vertical Tube ◽  
Particle Flow ◽  
Layer Model ◽  
Two Layer Model ◽  
Two Fluid Model ◽  
Two Fluid

A numerical study was carried out to investigate the performance of a two-layer model for predicting turbulent gas-particle flows in rough pipes. An Eulerian–Eulerian two-fluid formulation was used to model both the gas and solid phases for turbulent gas-particle flow in a vertical tube. The stresses developed in the particle phase were calculated using the kinetic theory of granular flows while the gas-phase stresses were described using an eddy viscosity model. The two-fluid model typically uses a two-equation k-ɛ model to describe the gas phase turbulence, which includes the suppression and enhancement effects due to the presence of particles. For comparison, a two-layer model was also implemented since it has the capability to include surface roughness. The current study examines the predictions of the two-layer model for both clear gas and gas-solid flows in comparison to the results of a conventional low Reynolds number model. The paper specifically documents the effects of surface roughness on the turbulence kinetic energy and granular temperature for gas-particle flow in both smooth and rough pipes.

scholarly journals Numerical Study of Shear Banding in Flows of Fluids Governed by the Rolie-Poly Two-Fluid Model via Stabilized Finite Volume Methods

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 810
Author(s):  
Jade Gesare Abuga ◽  
Tiri Chinyoka
Keyword(s):  
Finite Volume ◽  
Numerical Algorithm ◽  
Numerical Study ◽  
Fluid Model ◽  
Shear Banding ◽  
Numerical Algorithms ◽  
Viscoelastic Fluids ◽  
Two Fluid Model ◽  
Two Fluid ◽  
Good Agreement

The flow of viscoelastic fluids may, under certain conditions, exhibit shear-banding characteristics that result from their susceptibility to unusual flow instabilities. In this work, we explore both the existing shear banding mechanisms in the literature, namely; constitutive instabilities and flow-induced inhomogeneities. Shear banding due to constitutive instabilities is modelled via either the Johnson–Segalman or the Giesekus constitutive models. Shear banding due to flow-induced inhomogeneities is modelled via the Rolie–Poly constitutive model. The Rolie–Poly constitutive equation is especially chosen because it expresses, precisely, the shear rheometry of polymer solutions for a large number of strain rates. For the Rolie–Poly approach, we use the two-fluid model wherein the stress dynamics are coupled with concentration equations. We follow a computational analysis approach via an efficient and versatile numerical algorithm. The numerical algorithm is based on the Finite Volume Method (FVM) and it is implemented in the open-source software package, OpenFOAM. The efficiency of our numerical algorithms is enhanced via two possible stabilization techniques, namely; the Log-Conformation Reformulation (LCR) and the Discrete Elastic Viscous Stress Splitting (DEVSS) methodologies. We demonstrate that our stabilized numerical algorithms accurately simulate these complex (shear banded) flows of complex (viscoelastic) fluids. Verification of the shear-banding results via both the Giesekus and Johnson-Segalman models show good agreement with existing literature using the DEVSS technique. A comparison of the Rolie–Poly two-fluid model results with existing literature for the concentration and velocity profiles is also in good agreement.

A NUMERICAL STUDY OF TWO-PHASE FLOW USING A TWO-DIMENSIONAL TWO-FLUID MODEL

2004 ◽  
Vol 45 (10) ◽  
pp. 1049-1066 ◽  
Author(s):  
Moon-Sun Chung ◽  
Seung-Kyung Pak ◽  
Keun-Shik Chang
Keyword(s):  
Two Phase Flow ◽  
Numerical Study ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Dimensional ◽  
Two Phase ◽  
Two Fluid Model ◽  
Two Fluid

A Concise Numerical Model of Gas-Liquid Stratified Wavy Flow

2012 ◽  
Vol 198-199 ◽  
pp. 103-107
Author(s):  
Guo Zhen Li ◽  
Ya Lei Yuan
Keyword(s):  
Gas Phase ◽  
Fluid Model ◽  
Equation Model ◽  
Wall Function ◽  
Liquid Holdup ◽  
One Dimensional ◽  
Drop Velocity ◽  
Flow Parameters ◽  
Two Fluid Model ◽  
Two Fluid

On the basis of the conservation law of the flow field and the two-fluid model, a one-dimensional steady state hydraulics model of the gas-liquid stratified wavy flow is established. The method accounts for the effects of the turbulence through the use of the standard K-ε two-equation model of turbulence with the wall function method employed near the wall. The gas phase and the liquid phase in the wavy region are considered respectively as two points for simplification. The model permits the prediction of flow parameters such as liquid holdup,pressure drop, velocity profile and so on. It is easy to calculate and the result is compared with the experiments and other models and agrees well with them.

Study on Drag Coefficients for Two Groups of Bubbles

2004 ◽  
Author(s):  
Xiaodong Sun ◽  
Yang Liu ◽  
Basar Ozar ◽  
Mamoru Ishii ◽  
Joseph M. Kelly
Keyword(s):  
Gas Phase ◽  
Fluid Model ◽  
Interfacial Area ◽  
Current Approach ◽  
Two Phase ◽  
Drag Coefficients ◽  
Interfacial Area Transport ◽  
Wide Range ◽  
Two Fluid Model ◽  
Two Fluid

To apply the two-fluid model to a wide range of flow regimes in gas-liquid two-phase flows, the gas phase is categorized into two groups: small spherical/distorted bubbles as Group 1 and large cap/slug/churn-turbulent bubbles as Group 2 in the modeling of interfacial area transport. The interfacial transfer terms of momentum and energy for the gas phase are then divided into two groups accordingly in the implementation of the two-group interfacial area transport equation to the two-fluid model. Thus, the drag coefficients and the interfacial heat transfer for each group bubbles need to be developed. An approach has been sought for evaluating the drag coefficients of each bubble group based on a comprehensive experimental data base obtained in air-water upward flows in various size round pipes. Comparisons have been made with the theory of the drag coefficients and it was found that the agreement is not very satisfactory although the general trends can be predicted by the current approach.

scholarly journals 3D simulation of gas-laden liquid flows in centrifugal pumps and the assessment of two-fluid CFD methods

2020 ◽  
Vol 3 (3) ◽  
pp. 186-207 ◽  
Author(s):  
Markus Hundshagen ◽  
Michael Mansour ◽  
Dominique Thévenin ◽  
Romuald Skoda
Keyword(s):  
Gas Phase ◽  
Spatial Resolution ◽  
Single Phase ◽  
High Spatial Resolution ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Phase ◽  
Two Fluid Model ◽  
Liquid Flows ◽  
Two Fluid

Abstract An assessment of a two-fluid model assuming a continuous liquid and a dispersed gas phase for 3D computational fluid dynamics (CFD) simulations of gas/liquid flow in a centrifugal research pump is performed. A monodisperse two-fluid model, in conjunction with a statistical eddy-viscosity turbulence model, is utilized. By a comprehensive measurement database, a thorough assessment of model inaccuracies is enabled. The results on a horizontal diffuser flow reveal that the turbulence model is one main limitation of simulation accuracy for gas/liquid flows. Regarding pump flows, distinctions of single-phase and two-phase flow in a closed and semi-open impeller are figured out. Even single-phase flow simulations reveal challenging requirements on a high spatial resolution, e.g., of the rounded blade trailing edge and the tip clearance gap flow. In two-phase pump operation, gas accumulations lead to coherent gas pockets that are predicted partly at wrong locations within the blade channel. At best, a qualitative prediction of gas accumulations and the head drop towards increasing inlet gas volume fractions (IGVF) can be obtained. One main limitation of two-fluid methods for pump flow is figured out in terms of the violation of the dilute, disperse phase assumption due to locally high disperse phase loading within coherent gas accumulations. In these circumstances, bubble population models do not appear beneficial compared to a monodisperse bubble distribution. Volume-of-Fluid (VOF) methods may be utilized to capture the phase interface at large accumulated gas cavities, requiring a high spatial resolution. Thus, a hybrid model, i.e., a dispersed phase two-fluid model including polydispersity for flow regions with a dilute gas phase, should be combined with an interphase capturing model, e.g., in terms of VOF. This hybrid model, together with scale-resolving turbulence models, seems to be indispensable for a quantitative two-phase pump performance prediction.

scholarly journals Effect of liquid phase compressibility on modeling of gas-liquid two-phase flows using two-fluid model

2019 ◽  
Vol 23 (5 Part B) ◽  
pp. 3003-3013
Author(s):  
Vahid Shokri ◽  
Kazem Esmaeili
Keyword(s):  
Liquid Phase ◽  
Relative Velocity ◽  
Numerical Study ◽  
Fluid Model ◽  
Shock Capturing ◽  
Two Phase ◽  
Solution Field ◽  
Two Fluid Model ◽  
Flow Variables ◽  
Two Fluid

In this paper, a numerical study is performed in order to investigate the effect of the liquid phase compressibility two-fluid model. The two-fluid model is solved by using conservative shock capturing method. At the first, the two-fluid model is applied by assuming that the liquid phase is incompressible, then it is assumed that in three cases called water faucet case, large relative velocity shock pipe case, and Toumi?s shock pipe case, the liquid phase is compressible. Numerical results indicate that, if an intense pressure gradient is governed on the fluid-flow, single-pressure two-fluid model by assuming liquid phase incompressibility predicts the flow variables in the solution field more accurate than single-pressure two-fluid model by assuming liquid phase compressibility.

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