Showing papers on "Multiphase flow published in 2004"

Predictive pore-scale modeling of two-phase flow in mixed wet media

Abstract: [1] We show how to predict flow properties for a variety of porous media using pore-scale modeling with geologically realistic networks Starting with a network representation of Berea sandstone, the pore size distribution is adjusted to match capillary pressure for different media, keeping the rank order of pore sizes and the network topology fixed Then predictions of single and multiphase properties are made with no further adjustment of the model We successfully predict relative permeability and oil recovery for water wet, oil wet, and mixed wet data sets For water flooding we introduce a method for assigning contact angles to match measured wettability indices The aim of this work is not simply to match experiments but to use easily acquired data to predict difficult to measure properties Furthermore, the variation of these properties in the field, due to wettability trends and different pore structures, can now be predicted reliably

The TOUGH Codes—A Family of Simulation Tools for Multiphase Flow and Transport Processes in Permeable Media

Abstract: Numerical simulation has become a widely practiced andaccepted technique for studying flow and transport processes in thevadose zone and other subsurface flow systems. This article discusses asuite of codes, developed primarily at Lawrence Berkeley NationalLaboratory (LBNL), with the capability to model multiphase flows withphase change. We summarize history and goals in the development of theTOUGH codes, and present the governing equations for multiphase,multicomponent flow. Special emphasis is given to space discretization bymeans of integral finite differences (IFD). Issues of code implementationand architecture are addressed, as well as code applications,maintenance, and future developments.

Interfacial area measurements for unsaturated flow through a porous medium

Abstract: [1] Multiphase flow and contaminant transport in porous media are strongly influenced by the presence of fluid-fluid interfaces. Recent theoretical work based on conservation laws and the second law of thermodynamics has demonstrated the need for quantitative interfacial area information to be incorporated into multiphase flow models. We have used synchrotron based X-ray microtomography to investigate unsaturated flow through a glass bead column. Fully three-dimensional images were collected at points on the primary drainage curve and on the secondary imbibition and drainage loops. Analysis of the high-resolution images (17 micron voxels) allows for computation of interfacial areas and saturation. Corresponding pressure measurements are made during the course of the experiments. Results show the fluid-fluid interfacial area increasing as saturation decreases, reaching a maximum at saturations ranging from 20 to 35% and then decreasing as the saturation continues to zero. The findings support results of numerical studies reported in the literature.

Measurement of granular temperature and stresses in risers

Abstract: Detailed experimental velocity, particle concentration, and stresses for flow of particles in a vertical pipe, riser are needed for verification of various CFD models for multiphase flow. This is the principle-unsolved task of the Fluid Dynamics Multiphase Flow Consortium, organized by Dow Chemical Company. This study provides such information for flow of 530 μm glass beads in the fully developed flow region of a 7 m symmetric riser with a splash plate. Instantaneous particle-velocity distributions were obtained using a particle velocity imaging technique, and a probe inserted into the riser, while the particle concentrations were measured with a gamma-ray densitometer. Time-averaged particle-velocity distributions can be well represented by a parabolic- velocity distribution, with the mean velocity obtained from flux divided by the measured bulk density. The flow is very anisotropic. The radial granular-temperature profiles agree with an analytical expression similar to the thermal-temperature distribution in Poiseuille flow with viscous heat generation. A numerical solution for the standard isotropic model developed shows that the approximations made in the analytical solutions are reasonable. In the core, the normal Reynolds stresses are much smaller than the velocity averaged particle stresses, whereas near the wall the time averaged normal Reynolds stresses are large. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1760–1775, 2004

Linking Pressure and Saturation through Interfacial Areas in Porous Media

Abstract: [1] Using transparent microfluidic cells to study the two-phase properties of a synthetic porous medium, we establish that the interfacial area per volume between nonwetting and wetting fluids lifts the ambiguity associated with the hysteretic relationship between capillary pressure and saturation in porous media. The interface between the nonwetting and wetting phases is composed of two subsets: one with a unique curvature determined by the capillary pressure, and the other with a distribution of curvatures dominated by disjoining pressure. This work provides experimental support for recent theoretical predictions that the capillary-dominated subset plays a role analogous to a state variable. Any comprehensive description of multiphase flow properties must include this interfacial area with the traditional variables of pressure and fluid saturation.

Three-dimensional imaging of multiphase flow in porous media

Abstract: This paper reports progress in the 3D pore-scale micro-CT imaging of multiple fluid phases during drainage experiments in porous materials. Experiments performed on a sintered monodisperse bead pack and a Berea sandstone sample are described. It is observed that the residual (trapped) wetting phase in the sintered bead pack is present as pendular rings, bridges between adjacent grains and lenses within pore throats. Estimates of the residual wetting phase saturation are in accord with previous experiments and predictions on model bead packs. Relative permeabilities computed directly on the digitised images of the fluid phases are in good agreement with experimentally measured values for Berea sandstone. Two simple numerical methods for estimating two phase drainage saturation distributions directly from images are compared. Both methods give good agreement with the bead pack experiment. The match for Berea sandstone is poorer; differences may be due to variable wettability.

Multiphase Inverse Modeling: Review and iTOUGH2 Applications

Abstract: Calibration of a numerical process model against laboratory or field data is often referred to as ''inverse modeling'' As the numerical simulation models become more complex, the number of parameters to be estimated generally increases, requiring new testing, modeling, and inversion strategies The purpose of this survey is to review inverse modeling approaches for unsaturated and multiphase flow models The discussion focuses on applications rather than theoretical considerations, which have been previously reviewed in the context of saturated flow and transport modeling We also examine model parameterization issues, specifically the representation of heterogeneity through a limited number of variables that can be subjected to parameter estimation and uncertainty propagation analyses Different parameterization strategies are illustrated using the multiphase flow simulation-optimization code iTOUGH2 (Finsterle, 1999a,b,c) A comprehensive inverse modeling package (such as iTOUGH2, which includes automatic model calibration followed by an extensive residual, error, and uncertainty propagation analysis) is an essential tool to improve test design and data analysis of complex multiphase flow systems

Modeling of Granular Particle Damping Using Multiphase Flow Theory of Gas-Particle

Abstract: A theoretical model based on multiphase flow theory of gas-particle is developed to evaluate the granular particle damping characteristics. Expressions for the drag forces of the equivalent viscous damping and the Coulomb friction damping are formulated respectively. The nonlinear free vibration of an exemplified cantilever particle-damping beam is analyzed by using the averaging method based on the first approximation. Numerical results are also presented to illustrate general characteristics of the particle-damping beam. An experimental verification is performed, and a good correlation between the theoretical results and the experimental data shows that the theoretical work in this paper is valid.

Numerical modeling of geophysical granular flows: 2. Computer simulations of plinian clouds and pyroclastic flows and surges

Abstract: [1] Geophysical granular flows display complex nonlinear, nonuniform, and unsteady rheologies, depending on the volumetric grain concentration within the flow: kinetic, kinetic-collisional, and frictional. To account for the whole spectrum of granular rheologies (and hence concentrations), we have used and further developed for geophysical-atmospheric applications a multiphase computer model initially developed by U.S. Department of Energy laboratories: (Geophysical) Multiphase Flow with Interphase Exchange. As demonstrated in this manuscript, (G)MFIX can successfully simulate a large span of pyroclastic phenomena and related processes: plinian clouds, pyroclastic flows and surges, flow transformations, and depositional processes. Plinian cloud simulations agree well with the classical plume theory and historical eruptions in the upper altitude of the cloud (HT) versus mass flux diagram. At high mass flux (>107 kg/s), plinian clouds pulsate periodically with time because of the vertical propagations of acoustic-gravity waves within the clouds. The lowest undercooled temperature anomalies measured within the upper part of the column can be as low as −18 K, which agrees well with El Chichon and Mt. St. Helens eruptions. Vertical and horizontal speed profiles within the plinian cloud compare well with those inferred from simple plume models and from umbrella experiments. Pyroclastic flow and surge simulations show that both end-members are closely tight together; e.g., an initially diluted flow may generate a denser basal underflow, which will eventually outrun the expanded head of the flow. We further illustrate evidence of vertical and lateral flow transformation processes between diluted and concentrated flows, particularly laterally from a turbulent “maintained over time fluidized zone” near source. Our comprehensive granular rheological model and our simulations demonstrate that the main depositional process is mainly a progressive vertical aggradation.

Multiphase flow in deforming porous material

Abstract: A model for mechanical behaviour of saturated–unsaturated porous media is presented within the framework of thermodynamics of irreversible processes. It includes interfaces with thermodynamic properties between the constituents. The necessary balance equations are derived using averaging theories. Restrictions on the form of the constitutive equations are obtained by exploiting the entropy inequality according to the Coleman–Noll procedure. A particular form of the governing equations is then solved numerically. The validation of the model proposed through a comparison between experimental and numerical results and an application example concerning a tunnel fire conclude the paper. Copyright © 2004 John Wiley & Sons, Ltd.

Numerical modeling of geophysical granular flows: 1. A comprehensive approach to granular rheologies and geophysical multiphase flows

Abstract: [1] Geophysical granular materials display a wide variety of behaviors and features. Typically, granular flows (1) are multiphase flows, (2) are very dissipative over many different scales, (3) display a wide range of grain concentrations, and (4), as a final result of these previous features, display complex nonlinear, nonuniform, and unsteady rheologies. Therefore the objectives of this manuscript are twofold: (1) setting up a hydrodynamic model which acknowledges the multiphase nature of granular flows and (2) defining a comprehensive rheological model which accounts for all the different forms of viscous dissipations within granular flows at any concentration. Hence three important regimes within granular flows must be acknowledged: kinetic (pure free flights of grain), kinetic-collisional, and frictional. The momentum and energy transfer will be different according to the granular regimes, i.e., strain rate dependent in the kinetic and kinetic-collisional cases and strain rate independent in the frictional case. A “universal” granular rheological model requires a comprehensive unified stress tensor able to adequately describe viscous stress within the flow for any of these regimes, and without imposing a priori what regime will dominate over the others. The kinetic-collisional viscous regime is defined from a modified Boltzmann's kinetic theory of dense gas. The frictional viscous regime is defined from the plastic potential and the critical state theories which account for compressibility of granular matter (e.g., dilatancy, consolidation, and critical state). In the companion paper [Dartevelle et al., 2004] we will introduce a multiphase computer code, (G)MFIX, which accounts for all the granular regimes and rheology and present typical simulations of diluted (e.g., plinian clouds) and concentrated geophysical granular flows (i.e., pyroclastic flows and surges).

Multiphase Inverse Modeling

Abstract: Calibration of a numerical process model against laboratory or field data is often referred to as “inverse modeling.” As the numerical simulation models become more complex, the number of parameters to be estimated generally increases, requiring new testing, modeling, and inversion strategies. The purpose of this survey is to review inverse modeling approaches for unsaturated and multiphase flow models. The discussion focuses on applications rather than theoretical considerations, which have been previously reviewed in the context of saturated flow and transport modeling. We also examine model parameterization issues, specifically the representation of heterogeneity through a limited number of variables that can be subjected to parameter estimation and uncertainty propagation analyses. Different parameterization strategies are illustrated using the multiphase flow simulation–optimization code iTOUGH2. A comprehensive inverse modeling package (such as iTOUGH2, which includes automatic model calibration followed by an extensive residual, error, and uncertainty propagation analysis) is an essential tool to improve test design and data analysis of complex multiphase flow systems.

Multiphase Flow Dynamics 1 : Fundamentals

Abstract: Keywords: fluides : dynamique des Note: contient un CDRom Reference Record created on 2004-09-07, modified on 2011-09-01

Experimental study of liquid-gas flow structure effects on relative permeabilities in a fracture

Abstract: [1] Two-phase flow through fractured media is important in geothermal, nuclear, and petroleum applications. In this research an experimental apparatus was built to capture the unstable nature of the two-phase flow in a smooth-walled fracture and display the flow structures under different flow configurations in real time. The air-water relative permeability was obtained from experiment and showed deviation from the X curve behavior suggested by earlier studies. Through this work the relationship between the phase channel morphology and relative permeability in fractures was determined. A physical tortuous channel approach was proposed to quantify the effects of the flow structure. This approach could replicate the experimental results with a good accuracy. Other relative permeability models (viscous coupling model, X curve model, and Corey curve model) were also compared. Except for the viscous coupling model, these models did not interpret the experimental relative permeabilities as well as the proposed tortuous channel model. Hence we concluded that the two-phase relative permeability in fractures depends not only on liquid type and fracture geometry but also on the structure of the two-phase flow.

Flow structure of subcooled boiling flow in an internally heated annulus

Abstract: Local measurements of flow parameters were performed for vertical upward subcooled boiling flows in an internally heated annulus. The annulus channel consisted of an inner heater rod with a diameter of 19.1 mm and an outer round pipe with an inner diameter of 38.1 mm, and the hydraulic equivalent diameter was 19.1 mm. The double-sensor conductivity probe method was used for measuring local void fraction, interfacial area concentration, and interfacial velocity. A total of 11 data were acquired consisting of four inlet liquid velocities, 0.500, 0.664, 0.987 and1.22 m/s and two inlet liquid temperatures, 95.0 and 98.0 degrees Celsius. The constitutive equations for distribution parameter and drift velocity in the drift-flux model, and the semi-theoretical correlation for Sauter mean diameter, namely, interfacial area concentration, which were proposed previously, were validated by local flow parameters obtained in the experiment.

A numerical study of breaking waves

Abstract: This numerical study explores the physical processes involved in breaking waves. The two-dimensional, incompressible, unsteady Navier–Stokes equations are solved in sufficiently refined grids to capture viscous and capillary effects. The immiscible interface, characterized by a jump in density and viscosity, is embedded in the domain and a hybrid front tracking/capturing method is used to characterize the moving interface of this multiphase flow. A parametric study is conducted to assess the role of surface tension, Reynolds number, density, and viscosity on the breaking process, as well as their role in the vorticity redistribution and energy dissipation beneath the surface.