Solution Methods for Multi-Phase Flows

Yeoh, Guan Heng; Tu, Jiyuan

doi:10.1016/b978-0-08-046733-7.00003-5

Cited by 51 publications

(56 citation statements)

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“…The values between them indicate the existence of an interface and is a measure of the relative concentration of the fluids. In general, the approach of applying volume fractions is computationally more economical than using markers following the interface since only one value is assigned to each computational cell [25]. Other advantage is that only one conservation equation is required to be solved for the propagation of the volume fractions throughout the domain, in addition to the mass and momentum conservation equations.…”

Section: Multiphase Flow Modelingmentioning

confidence: 99%

“…One drawback of the VOF method is that, while solving the volume fraction advection equation, special interpolation schemes are required for preserving accurate results in the mass conservation equation. Conventional advection schemes, such as Second-order Upwind and QUICK, smear the step profile of the interface over several computational cells due to numerical diffusion [25]. To overcome this situation, special methods such as CICSAM [27] or line techniques are needed.…”

Section: Governing Equationsmentioning

confidence: 99%

“…To overcome this situation, special methods such as CICSAM [27] or line techniques are needed. In this study, the Piecewise Linear Interface Construction (PLIC) algorithm, a line technique first proposed by Youngs [28], was applied due to its ability to render a sharp and clear interface without numerical diffusion [25]. This scheme is briefly presented next.…”

Section: Governing Equationsmentioning

confidence: 99%

See 2 more Smart Citations

Numerical study of the churn-slug transition dynamics in vertical upward air-water flows

Imada¹,

Saltara²,

Bali˜no³

2013

Computational Methods in Multiphase Flow VII

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In gas-liquid two-phase flows through vertical ducts, the spatial distribution of phases may assume several configurations, known as flow patterns. Slug and churn patterns are characterized by an unsteady behaviour and their boundary is a subject of interest for many researchers. Different descriptions of mechanisms occurring at churn/slug transition may be found in the literature. One transition process is described by Taitel et al. (Modelling flow pattern transitions for steady upward gas-liquid flow in vertical tubes. AIChE Journal, 26, pp. 345-354, 1980), in which churn flow is an entrance condition observed upstream of a developed slug flow if there is sufficient pipe length for this to happen. In the present work, vertical upward air-water flows through a 2-inch i.d. tube are simulated with the commercial finite-volume-based code FLUENT, aiming to study this churn/slug transition process through spatial and temporal phase distribution visualizations and statistical analyses of void fraction histories at points along the domain. The incompressible Volume of Fluid (VOF) formulation allied to a Piecewise Linear Interface Construction (PLIC) technique is applied to capture the distribution of phases throughout three-dimensional domains. Turbulence effects are accounted through the Realizable k-epsilon model. Three different tube lengths and two sets of superficial velocities are studied in order to understand their influence in liquid slug collapse and bubble coalescence processes. Void fraction histories at points distributed along the duct centerline are stored during a simulation time long enough to provide statistical data with reasonable errors. Fast Fourier Transform analyses are used to verify the transition point and flow characteristic frequencies. Probability distributions of void fraction at cross sections along the tube are also evaluated. The VOF method was able to qualitatively capture the mechanisms of churn/slug transition processes. Results for entrance length and frequencies are

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Section: Multiphase Flow Modelingmentioning

confidence: 99%

Section: Governing Equationsmentioning

confidence: 99%

Section: Governing Equationsmentioning

confidence: 99%

See 1 more Smart Citation

Numerical study of the churn-slug transition dynamics in vertical upward air-water flows

Imada¹,

Saltara²,

Bali˜no³

2013

Computational Methods in Multiphase Flow VII

View full text Add to dashboard Cite

show abstract

“…Because of its flexibility in terms of installation, low maintenance cost and a high level of automation pneumatic conveying is a convincing technology in particular in the field of chemical, process and civil engineering [1,2]. The occurring transport modes are dependent on the geometry of the pipes, the conveying velocity, the particle diameter and the mass load of the system [3].…”

Section: Introductionmentioning

confidence: 99%

“…Some simulation methods have been proposed which generally differ by the description of the solid phase. The Euler-Euler method, also often named two-fluid model, treats the solid phase as a continuum interacting with the fluid continuum [7] and assumes that the particle assembly behaves like a fluid [2]. Basically, this approach has been developed for high solid concentrations where avoidance of individual particle tracking reduces the computational effort, but in the context of dense pneumatic conveying it is hard to fulfill the continuum hypotheses for the whole computational domain (e.g.…”

Section: Introductionmentioning

confidence: 99%

Coupled DEM‐CFD Simulation of Pneumatically Conveyed Granular Media

et al. 2010

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A DEM-CFD coupling for the simulation of gas-solid flows was successfully implemented and simulations were performed for the application to industrial-scale pneumatic conveying. Therefore, all particle collisions and phase interactions were considered and porosity determination was optimized. The aim of this work is to show the applicability of the presented simulation model to the different regimes of pneumatic conveying systems. As a first test case a dense vertical pneumatic conveying system was chosen and an individual plug was investigated in detail. Variations of the conveying air velocity were also considered. As a second test case dilute conveying in a horizontal-to-vertical pipe bend was simulated. The occurrence of roping and the reduction of particle velocity is of high interest for the design of specific pneumatic systems. It is shown that both regimes can be captured reasonably well and the results are rich in details.

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Testing a simple model of gas bubble dynamics in porous media

Ramírez

Baird

Coulthard

et al. 2015

Water Resources Research

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Bubble dynamics in porous media are of great importance in industrial and natural systems. Of particular significance is the impact that bubble-related emissions (ebullition) of greenhouse gases from porous media could have on global climate (e.g., wetland methane emissions). Thus, predictions of future changes in bubble storage, movement, and ebullition from porous media are needed. Methods exist to predict ebullition using numerical models, but all existing models are limited in scale (spatial and temporal) by high computational demands or represent porous media simplistically. A suitable model is needed to simulate ebullition at scales beyond individual pores or relatively small collections (<10 24 m 3 ) of connected pores. Here we present a cellular automaton model of bubbles in porous media that addresses this need. The model is computationally efficient, and could be applied over large spatial and temporal extent without sacrificing fine-scale detail. We test this cellular automaton model against a physical model and find a good correspondence in bubble storage, bubble size, and ebullition between both models. It was found that porous media heterogeneity alone can have a strong effect on ebullition. Furthermore, results from both models suggest that the frequency distributions of number of ebullition events per time and the magnitude of bubble loss are strongly right skewed, which partly explains the difficulty in interpreting ebullition events from natural systems.

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Solution Methods for Multi-Phase Flows

Cited by 51 publications

References 0 publications

Numerical study of the churn-slug transition dynamics in vertical upward air-water flows

Numerical study of the churn-slug transition dynamics in vertical upward air-water flows

Coupled DEM‐CFD Simulation of Pneumatically Conveyed Granular Media

Testing a simple model of gas bubble dynamics in porous media

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