scholarly journals Gas migration experiments in bentonite: implications for numerical modelling

2012 ◽  
Vol 76 (8) ◽  
pp. 3279-3292 ◽  
Author(s):  
C. C. Graham ◽  
J. F. Harrington ◽  
R. J. Cuss ◽  
P. Sellin
Keyword(s):  
Gas Phase ◽  
Gas Permeability ◽  
Radioactive Decay ◽  
Phase Flow ◽  
Gas Migration ◽  
Full Understanding ◽  
Two Phase ◽  
Key Features ◽  
Development And Validation ◽  
Further Development

AbstractIn the Swedish KBS-3 repository concept, there is potential for gas to be generated from corrosion of ferrous materials under anoxic conditions, combined with the radioactive decay of the waste and radiolysis of water. A full understanding of the probable behaviour of this gas phase within the engineered barrier system (EBS) is therefore required for performance assessment. We demonstrate key features from gas transport experiments on pre-compacted Mx80 bentonite, under laboratory and field conditions, and discuss their implications in terms of a conceptual model for gas migration behaviour. On both scales, major gas entry is seen to occur close to the sum of the porewater and swelling pressures of the bentonite. In addition, gas pressure at breakthrough is profoundly sensitive to the number and location of available sinks for gas escape. Observations of breakthrough can be explained by the creation of dilatational pathways, resulting in localized changes in the monitored porewater pressures and total stresses. These pathways are highly unstable, evolving spatially and temporally, and must consequently influence the gas permeability as their distribution/geometry develops.Such observations are poorly embodied by conventional concepts of two-phase flow, which do not fully represent the key processes involved. Although dilatancy based models provide a better description of these processes, the paucity of data limits further development and validation of these models at present.

Experimental Study of Gas Permeabilities and Breakthrough Pressures in Clays

1996 ◽  
Vol 465 ◽  
Author(s):  
K. Tanai ◽  
T. Kanno ◽  
C. Gallé
Keyword(s):  
Two Phase Flow ◽  
Gas Permeability ◽  
Phase Flow ◽  
Gas Migration ◽  
Two Phase ◽  
Saturation State ◽  
Flow Models ◽  
Water Permeation ◽  
Compacted Bentonite ◽  
Breakthrough Pressure

ABSTRACTIn this study, gas migration experiments in unsaturated and saturated states were carried out to clarify the fundamental gas migration characteristics in compacted bentonite to be used for the geological disposal of high-level radioactive waste. In unsaturated experiments, the gas permeability for Japanese bentonite (Kunigel VI) as a function of degree of saturation was measured to examine the applicability of conventional two-phase flow models to compacted bentonite. The intrinsic permeability obtained in this study was about five orders of magnitude larger than that obtained in water permeation tests with the same density. The difference seems to originate from the change of pore structure due to the swelling phenomenon of the bentonite. Since these effects have not been evaluated quantitatively yet, various relative gas permeability functions of conventional two-phase flow models were applied as a first approximation.Saturated experiments designed to simulate the gas migration phenomenon in a repository for the waste were carried out to obtain relationship between breakthrough and swelling pressures using Kunigel VI and French Fo-Ca clay in saturation state. The reproducibility of the breakthrough pressure was also examined for Kunigel VI bentonite. The breakthrough pressure was almost the same as swelling pressure irrespective of the type of clay. As to the reproducibility of breakthrough pressure, it was observed that first and second breakthrough pressures were almost the same for Kunigel VI specimens with the dry densities of 1.7 and 1.8 g/cm3.

Numerical Analysis of Two-Phase Pipe Flow of Liquid Helium Using Multi-Fluid Model

2001 ◽  
Vol 123 (4) ◽  
pp. 811-818 ◽  
Author(s):  
Jun Ishimoto ◽  
Mamoru Oike ◽  
Kenjiro Kamijo
Keyword(s):  
Phase Transition ◽  
Gas Phase ◽  
Liquid Helium ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Numerical Results ◽  
Phase Flow ◽  
Two Dimensional ◽  
Two Phase ◽  
Normal Fluid

The two-dimensional characteristics of the vapor-liquid two-phase flow of liquid helium in a pipe are numerically investigated to realize the further development and high performance of new cryogenic engineering applications. First, the governing equations of the two-phase flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model are presented and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the two-phase flow of liquid helium is shown in detail, and it is also found that the phase transition of the normal fluid to the superfluid and the generation of superfluid counterflow against normal fluid flow are conspicuous in the large gas phase volume fraction region where the liquid to gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase. According to these theoretical results, the fundamental characteristics of the cryogenic two-phase flow are predicted. The numerical results obtained should contribute to the realization of advanced cryogenic industrial applications.

scholarly journals Feasibility Study on Downhole Gas–Liquid Separator Design and Experiment Based on the Phase Isolation Method

2021 ◽  
Vol 11 (21) ◽  
pp. 10496
Author(s):  
Yuntong Yang ◽  
Zhaoyu Jiang ◽  
Lianfu Han ◽  
Wancun Liu ◽  
Xingbin Liu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Gas Phase ◽  
Separation Efficiency ◽  
Dynamic Test ◽  
Phase Flow ◽  
Total Flow ◽  
Total Flow Rate ◽  
Two Phase ◽  
Oil Gas ◽  
Liquid Separator

As oil exploitation enters its middle and late stages, formation pressure drops, and crude oil degases. In production profile logging, the presence of the gas phase will affect the initial oil–water two-phase flowmeter’s flow measurement results. In order to eliminate gas-phase interference and reduce measurement costs, we designed a downhole gas–liquid separator (DGLS) suitable for low flow, high water holdup, and high gas holdup. We based it on the phase isolation method. Using a combination of numerical simulation and fluid dynamic measurement experiments, we studied DGLS separation efficiency separately in the two cases of gas–water two-phase flow and oil–gas–water three-phase flow. Comparative analysis of the numerical simulation calculation and dynamic test results showed that: the VOF model constructed based on k−ε the equation is nearly identical to the dynamic test, and can be used to analyze DGLS separation efficiency; the numerical simulation results of the gas–water two-phase flow show that when the total flow rate is below 20 m3/d, the separation efficiency surpasses 90%. The oil–gas–water three-phase’s numerical simulation results show that the oil phase influences separation efficiency. When the total flow rate is 20 m3/d–50 m3/d and gas holdup is low, the DGLS’s separation efficiency can exceed 90%. Our experimental study on fluid dynamics measurement shows that the DGLS’s applicable range is when the gas mass is 0 m3/d~15 m3/d, and the water holdup range is 50%~100%. The research presented in this article can provide a theoretical basis for the development and design of DGLSs.

scholarly journals Modeling of Interior Ballistic Gas-Solid Flow Using a Coupled Computational Fluid Dynamics-Discrete Element Method

2013 ◽  
Vol 80 (3) ◽  
Author(s):  
Cheng Cheng ◽  
Xiaobing Zhang
Keyword(s):  
Discrete Element Method ◽  
Gas Phase ◽  
Two Phase Flow ◽  
Discrete Element ◽  
Particle Collision ◽  
Contact Detection ◽  
Reconstruction Method ◽  
Phase Flow ◽  
Two Phase ◽  
Element Method

In conventional models for two-phase reactive flow of interior ballistic, the dynamic collision phenomenon of particles is neglected or empirically simplified. However, the particle collision between particles may play an important role in dilute two-phase flow because the distribution of particles is extremely nonuniform. The collision force may be one of the key factors to influence the particle movement. This paper presents the CFD-DEM approach for simulation of interior ballistic two-phase flow considering the dynamic collision process. The gas phase is treated as a Eulerian continuum and described by a computational fluid dynamic method (CFD). The solid phase is modeled by discrete element method (DEM) using a soft sphere approach for the particle collision dynamic. The model takes into account grain combustion, particle-particle collisions, particle-wall collisions, interphase drag and heat transfer between gas and solid phases. The continuous gas phase equations are discretized in finite volume form and solved by the AUSM+-up scheme with the higher order accurate reconstruction method. Translational and rotational motions of discrete particles are solved by explicit time integrations. The direct mapping contact detection algorithm is used. The multigrid method is applied in the void fraction calculation, the contact detection procedure, and CFD solving procedure. Several verification tests demonstrate the accuracy and reliability of this approach. The simulation of an experimental igniter device in open air shows good agreement between the model and experimental measurements. This paper has implications for improving the ability to capture the complex physics phenomena of two-phase flow during the interior ballistic cycle and to predict dynamic collision phenomena at the individual particle scale.

Extended two-phase flow model with mechanical capability to simulate gas migration in bentonite

2014 ◽  
Vol 400 (1) ◽  
pp. 545-562 ◽  
Author(s):  
Y. Tawara ◽  
A. Hazart ◽  
K. Mori ◽  
K. Tada ◽  
T. Shimura ◽  
...  
Keyword(s):  
Flow Model ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Gas Migration ◽  
Two Phase

Flow Structures and Frictional Characteristics on Two-Phase Flow in Microchannels in PEM Fuel Cells

2005 ◽  
Author(s):  
Eon Soo Lee ◽  
Carlos H. Hidrovo ◽  
Julie E. Steinbrenner ◽  
Fu-Min Wang ◽  
Sebastien Vigneron ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Gas Phase ◽  
Single Phase ◽  
Film Flow ◽  
Two Phase Flow ◽  
Water Injection ◽  
Injection Rate ◽  
Flow Structures ◽  
Phase Flow ◽  
Two Phase

This experimental paper presents a study of gas-liquid two phase flow in rectangular channels of 500μm × 45μm and 23.7mm long with different wall conditions of hydrophilic and hydrophobic surface, in order to investigate the flow structures and the corresponding friction factors of simulated microchannels of PEMFC. The main flow in the channel is air and liquid water is injected at a single or several discrete locations in one side wall of the channel. The flow structure of liquid water in hydrophilic wall conditioned channel starts from wavy flow, develops to stable stratified film flow, and then transits to unstable fluctuating film flow, as the pressure drop and the flow velocity of air increase from around 10 kPa to over 100 kPa. The flow structure in hydrophobic channel develops from the slug flow to slug-and-film flow with increasing pressure drop and flow velocity. The pressure drop for single phase flow is measured for a base line study, and the fRe product is in close agreement with the theoretical value (fRe = 85) of the conventional laminar flow of aspect ratio 1:11. At the low range of water injection rate, the gas phase fRe product of the two phase flow based on the whole channel area was not substantially affected by the water introduction. However, as the water injection rate increases up to 100 μL/min, the gas phase fRe product based on the whole channel area deviates highly from the single phase theoretical value. The gas phase fRe product with the actual gas phase area corrected by the liquid phase film thickness agrees with the single phase theoretical value.

Development of Sodium Two-Phase Flow Model for KALIMER Core Analysis

2002 ◽  
Author(s):  
W. P. Chang ◽  
Dohee Hahn
Keyword(s):  
Liquid Metal ◽  
Single Phase ◽  
System Analysis ◽  
Flow Model ◽  
Two Phase Flow ◽  
Water System ◽  
Phase Flow ◽  
Two Phase ◽  
Applicable Range ◽  
Further Development

An algorithm for sodium boiling is developed in order to extend the applicability of SSC-K, which is a main system analysis code for the KALIMER (Korea Advanced LIquid MEtal Reactor) conceptual design. As the capability of the current SSC-K version is limited to simulation of only a single-phase sodium flow, its applicable range should not be enough to assess the fuel integrity under some of HCDA (Hypothetical Core Disruptive Accident) initiating events where sodium boiling is anticipated. The two-phase flow model similar to that used for the light water system is known to be no more effective directly to liquid metal reactors, because the phenomena observed between two reactor coolant systems are definitely different. The developing algorithm is based on a multiple-bubble slug ejection model, which allows a finite number of bubbles in a channel at any time. The present work is a continuous effort following the former study to confirm a qualitative acceptance on the model. Since the model has been applied only to the active fuel region in the former study, a part of its qualification seems to have already been demonstrated. For its application to the whole KALIMER core channel, however, the model needs to be examined the applicability to the fuel regions other than the active fuel. The present study primarily focuses on that point. In a result, although the model may be improved in a sense through the present study over the previous modeling, a clear limitation is also confirmed with the validity of the model. The further development, therefore, is required for this model to achieve its goal by resolving such limitations.

AMADEUS Project and Microscopic Simulation of Boiling Two-Phase Flow by the Lattice-Boltzmann Method

1997 ◽  
Vol 08 (04) ◽  
pp. 843-858 ◽  
Author(s):  
Yasuyoshi Kato ◽  
Koji Kono ◽  
Takeshi Seta ◽  
Daniel Martínez ◽  
Shiyi Chen
Keyword(s):  
Phase Transition ◽  
Gas Phase ◽  
Lattice Boltzmann ◽  
Bubble Dynamics ◽  
Two Phase Flow ◽  
Phase Interface ◽  
Lattice Boltzmann Model ◽  
Phase Flow ◽  
Two Phase ◽  
Boltzmann Model

A two-dimensional lattice-Boltzmann model with a hexagonal lattice is developed to simulate a boiling two-phase flow microscopically. Liquid-gas phase transition and bubble dynamics, including bubble formation, growth and deformation, are modeled by using an interparticle potential based on the van der Waals equation of state. Thermohydrodynamics is incorporated into the model by adding extra velocities to define temperature. The lattice-Boltzmann model is solved by a finite difference scheme so that numerical stability can be ensured at large discontinuity across the liquid-gas phase boundary and the narrow phase interface thickness can be attained. It is shown from numerical simulations that the model has the ability to reproduce phase transition, bubble dynamics and thermohydrodynamics while assuring numerical instability and narrow phase interface.

scholarly journals Computational Fluid Dynamics Simulations of Gas-liquid Two-phase Flow Characteristics through a Vertical to Horizontal Right Angled Elbow

2017 ◽  
Vol 30 (1&2) ◽  
pp. 1-16 ◽  
Author(s):  
N. Z. Aung ◽  
T. Yuwono
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Phase ◽  
Test Section ◽  
Two Phase Flow ◽  
Liquid Velocity ◽  
Phase Flow ◽  
Cfd Simulations ◽  
Two Phase ◽  
Horizontal Pipe

Having a clear understanding on the phase distribution of gas-liquid two-phase flow through elbow bends is vital in mixing and separation system designs. This paper presents the computational fluid dynamics (CFD) simulations and experimental observations of gas-liquid two-phase flow pattern characteristic through a vertical to horizontal right angled (90°) elbow. Experimental observations were conducted in a transparent test section that consisted of a vertical pipe, elbow bend and horizontal pipe with an inside diameter of 0.036 m. The CFD simulations were performed by using a computer software package, FLUENT 6.2. Bubbly flow conditions were created in the vertical test section with the variation of superficial liquid Reynolds number from 13 497 to 49 488 and volumetric gas quality from 0.05 to 0.2. The CFD results showed a good agreement with experimental results in the following observations. The results showed that gas-liquid flow pattern inside and downstream of the elbow bend mainly depended on liquid velocity and it is also influenced by gas quality at high liquid velocities. At lower liquid velocities, gas-liquid separation began early in the elbow bend and gas-phase migrated to outer bend. Then, it smoothly transformed to stratified flow at elbow outlet. When the liquid velocity was further increased, the liquid phase occupied the outer bend rubbing the gas phase to the inner bend and delayed the formation of gas layer in the horizontal pipe. The increase of gas quality in higher liquid velocities promoted gas core formation at the elbow exit and caused wavy gas layers at the downstream of the elbow.

Influence of the Fin on Two-Dimensional Characteristics of Dispersed Flow With Wall Liquid Film in the Vicinity of Obstacle

2002 ◽  
Author(s):  
Zoran V. Stosic ◽  
Vladimir D. Stevanovic ◽  
Akimi Serizawa
Keyword(s):  
Liquid Film ◽  
Gas Phase ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Film Surface ◽  
Phase Flow ◽  
Atmospheric Conditions ◽  
Two Phase ◽  
Positive Effects ◽  
Rod Bundle

Spacers have positive effects on the heat transfer enhancement and critical heat flux (CHF) increase downstream of their location in the boiling channel. These effects are further increased by the inclusion of the fin on the spacer rear edge. Numerical simulation of a separation in a high void gas phase and dispersed droplets flow around a spacer, with a liquid film flowing on the wall, is performed. Mechanisms leading to the CHF increase due to the two-phase flow separation and liquid film thickening downstream the spacer are demonstrated. Numerical simulations of gas phase, entrained droplets and wall liquid film flows were performed with the three-fluid model and with the application of the high order numerical scheme for the liquid film surface interface tracking. Predicted is a separation of gas and entrained droplets streams around the spacer without and with a fin inclined 30 and 60 degrees to the wall, as well as a change of wall liquid film thickness in the vicinity of spacer. Results of liquid film dynamic behaviour are compared with the recently obtained experimental results. Multi-dimensional characteristics of surface waves on the liquid film were measured with newly developed ultrasonic transmission technique in a 3×3 rod bundle test section with air-water flow under atmospheric conditions. Obtained numerical results are in good agreement with experimental observations. The presented investigation gives insight into the complex mechanisms of separated two-phase flow with wall liquid film around the spacer and support thermal-hydraulic design and optimisation of flow obstacles in various thermal equipments.

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