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Preface: Recent Advances in Modeling Multiphase Flow and Transportwith the TOUGH Family of Codes

Description: A symposium on research carried out using the TOUGH family of numerical codes was held from May 15 to 17, 2006, at the Lawrence Berkeley National Laboratory. This special issue of the 'Vadose Zone Journal' contains revised and expanded versions of a selected set of papers presented at this symposium (TOUGH Symposium 2006; http://esd.lbl.gov/TOUGHsymposium), all of which focus on multiphase flow, including flow in the vadose zone.
Date: November 15, 2007
Creator: Liu, Hui-Hai & Illangasekare, Tissa H.
Partner: UNT Libraries Government Documents Department

iTOUGH2 Command Reference

Description: iTOUGH2 is a program for parameter estimation, sensitivity analysis, and uncertainty propagation analysis. It is based on the TOUGH2 simulator for non-isothermal multiphase flow in fractured and porous media. This report contains a detailed description of all iTOUGH2 commands.
Date: June 18, 2002
Creator: Finsterle, Stefan
Partner: UNT Libraries Government Documents Department

iTOUGH2 Sample Problems

Description: iTOUGH2 is a program for parameter estimation, sensitivity analysis, and uncertainty propagation analysis. It is based on the TOUGH2 simulator for non-isothermal multiphase flow in fractured and porous media. This report contains a collection of iTOUGH2 sample problems.
Date: June 18, 2002
Creator: Finsterle, Stefan
Partner: UNT Libraries Government Documents Department

Multiphase Flow in Complex Fracture Apertures under a Wide Range of Flow Conditions

Description: A better understanding of multiphase flow through fractures requires knowledge of the detailed physics of interfacial flows at the microscopic pore scale. The objective of our project was to develop tools for the simulation of such phenomena. Complementary work was performed by a group led by Dr.~Paul Meakin of the Idaho National Engineering and Environmental Laboratory. Our focus was on the lattice-Boltzmann (LB) method. In particular, we studied both the statics and dynamics of contact lines where two fluids (wetting and non-wetting) meet solid boundaries. Previous work had noted deficiencies in the way LB methods simulate such interfaces. Our work resulted in significant algorithmic improvements that alleviated these deficiencies. As a result, we were able to study in detail the behavior of the dynamic contact angle in flow through capillary tubes. Our simulations revealed that our LB method reproduces the correct scaling of the dynamic contact angle with respect to velocity, viscosity, and surface tension, without specification of an artificial slip length. Further study allowed us to identify the microscopic origin of the dynamic contact angle in LB methods. These results serve to delineate the range of applicability of multiphase LB methods to flows through complex geometries.
Date: December 12, 2006
Creator: Rothman, Daniel H.
Partner: UNT Libraries Government Documents Department

Numerical and Physical Modelling of Bubbly Flow Phenomena - Final Report to the Department of Energy

Description: This report describes the main features of the results obtained in the course of this project. A new approach to the systematic development of closure relations for the averaged equations of disperse multiphase flow is outlined. The focus of the project is on spatially non-uniform systems and several aspects in which such systems differ from uniform ones are described. Then, the procedure used in deriving the closure relations is given and some explicit results shown. The report also contains a list of publications supported by this grant and a list of the persons involved in the work.
Date: December 21, 2004
Creator: Prosperetti, Andrea
Partner: UNT Libraries Government Documents Department

The TOUGH codes - a family of simulation tools for multiphase flowand transport processes in permeable media

Description: 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.
Date: August 8, 2003
Creator: Pruess, Karsten
Partner: UNT Libraries Government Documents Department

Estimating large-scale fracture permeability of unsaturatedrockusing barometric pressure data

Description: We present a three-dimensional modeling study of gas flow inthe unsaturated fractured rock of Yucca Mountain. Our objective is toestimate large-scale fracture permeability, using the changes insubsurface pneumatic pressure in response to barometric pressure changesat the land surface. We incorporate the field-measured pneumatic datainto a multiphase flow model for describing the coupled processes ofliquid and gas flow under ambient geothermal conditions. Comparison offield-measured pneumatic data with model-predicted gas pressures is foundto be a powerful technique for estimating the fracture permeability ofthe unsaturated fractured rock, which is otherwise extremely difficult todetermine on the large scales of interest. In addition, this studydemonstrates that the multi-dimensional-flow effect on estimatedpermeability values is significant and should be included whendetermining fracture permeability in heterogeneous fracturedmedia.
Date: May 17, 2005
Creator: Wu, Yu-Shu; Zhang, Keni & Liu, Hui-Hai
Partner: UNT Libraries Government Documents Department


Description: Water hammer during multi-phase flow is rather complex, but in some cases an upper limit to the pressure surge magnitude during water hammer can be estimated. In the case considered here, a two mile long pipeline with a single high point was permitted to partially drain. Due to gravitational effects, air bubbles up through the pipe line to its highest point, but the time required for air to reach the top of the pipe is rather long. Consequently, some transients caused by valve operations are affected by air entrapment and some are not. The intent of this research was to investigate the complex interactions between air, water vapor, and liquid during water hammer in a long pipe with one end of the pipe open to atmospheric conditions. To understand the system dynamics, experimental data was obtained from a long pipeline with an open end and also from a short, transparent tube. Transient calculations were performed for valve closures and pump operations as applicable. The limitations of available calculation techniques were considered in detail.
Date: June 9, 2008
Creator: Leishear, R
Partner: UNT Libraries Government Documents Department

Advanced Vadose Zone Simulations Using TOUGH

Description: The vadose zone can be characterized as a complex subsurfacesystem in which intricate physical and biogeochemical processes occur inresponse to a variety of natural forcings and human activities. Thismakes it difficult to describe, understand, and predict the behavior ofthis specific subsurface system. The TOUGH nonisothermal multiphase flowsimulators are well-suited to perform advanced vadose zone studies. Theconceptual models underlying the TOUGH simulators are capable ofrepresenting features specific to the vadose zone, and of addressing avariety of coupled phenomena. Moreover, the simulators are integratedinto software tools that enable advanced data analysis, optimization, andsystem-level modeling. We discuss fundamental and computationalchallenges in simulating vadose zone processes, review recent advances inmodeling such systems, and demonstrate some capabilities of the TOUGHsuite of codes using illustrative examples.
Date: February 1, 2007
Creator: Finsterle, S.; Doughty, C.; Kowalsky, M.B.; Moridis, G.J.; Pan,L.; Xu, T. et al.
Partner: UNT Libraries Government Documents Department

Ensemble phase averaging equations for multiphase flows in porous media, part I: the bundle-of-tubes model

Description: A bundle-of-tubes construct is used as a model system to study ensemble averaged equations for multiphase flow in a porous material. Momentum equations for the fluid phases obtained from the method are similar to Darcy's law, but with additional terms. We study properties of the additional terms, and the conditions under which the averaged equations can be approximated by the diffusion model or the extended Darcy's law as often used in models for multiphase flows in porous media. Although the bundle-of-tubes model is perhaps the simplest model for a porous material, the ensemble averaged equation technique developed in this paper assumes the very same form in more general treatments described in Part 2 of the present work (Zhang 2009). Any model equation system intended for the more general cases must be understood and tested first using simple models. The concept of ensemble phase averaging is dissected here in physical terms, without involved mathematics through its application to the idealized bundle-of-tubes model for multiphase flow in porous media.
Date: January 1, 2008
Creator: Yang, Dali; Zhang, Duan & Currier, Robert
Partner: UNT Libraries Government Documents Department

Solving iTOUGH2 simulation and optimization problems using the PEST protocol

Description: The PEST protocol has been implemented into the iTOUGH2 code, allowing the user to link any simulation program (with ASCII-based inputs and outputs) to iTOUGH2's sensitivity analysis, inverse modeling, and uncertainty quantification capabilities. These application models can be pre- or post-processors of the TOUGH2 non-isothermal multiphase flow and transport simulator, or programs that are unrelated to the TOUGH suite of codes. PEST-style template and instruction files are used, respectively, to pass input parameters updated by the iTOUGH2 optimization routines to the model, and to retrieve the model-calculated values that correspond to observable variables. We summarize the iTOUGH2 capabilities and demonstrate the flexibility added by the PEST protocol for the solution of a variety of simulation-optimization problems. In particular, the combination of loosely coupled and tightly integrated simulation and optimization routines provides both the flexibility and control needed to solve challenging inversion problems for the analysis of multiphase subsurface flow and transport systems.
Date: February 1, 2011
Creator: Finsterle, S.A. & Zhang, Y.
Partner: UNT Libraries Government Documents Department

A truncated Levenberg-Marquardt algorithm for the calibration of highly parameterized nonlinear models

Description: We propose a modification to the Levenberg-Marquardt minimization algorithm for a more robust and more efficient calibration of highly parameterized, strongly nonlinear models of multiphase flow through porous media. The new method combines the advantages of truncated singular value decomposition with those of the classical Levenberg-Marquardt algorithm, thus enabling a more robust solution of underdetermined inverse problems with complex relations between the parameters to be estimated and the observable state variables used for calibration. The truncation limit separating the solution space from the calibration null space is re-evaluated during the iterative calibration process. In between these re-evaluations, fewer forward simulations are required, compared to the standard approach, to calculate the approximate sensitivity matrix. Truncated singular values are used to calculate the Levenberg-Marquardt parameter updates, ensuring that safe small steps along the steepest-descent direction are taken for highly correlated parameters of low sensitivity, whereas efficient quasi-Gauss-Newton steps are taken for independent parameters with high impact. The performance of the proposed scheme is demonstrated for a synthetic data set representing infiltration into a partially saturated, heterogeneous soil, where hydrogeological, petrophysical, and geostatistical parameters are estimated based on the joint inversion of hydrological and geophysical data.
Date: October 15, 2010
Creator: Finsterle, S. & Kowalsky, M.B.
Partner: UNT Libraries Government Documents Department

Error handling strategies in multiphase inverse modeling

Description: Parameter estimation by inverse modeling involves the repeated evaluation of a function of residuals. These residuals represent both errors in the model and errors in the data. In practical applications of inverse modeling of multiphase flow and transport, the error structure of the final residuals often significantly deviates from the statistical assumptions that underlie standard maximum likelihood estimation using the least-squares method. Large random or systematic errors are likely to lead to convergence problems, biased parameter estimates, misleading uncertainty measures, or poor predictive capabilities of the calibrated model. The multiphase inverse modeling code iTOUGH2 supports strategies that identify and mitigate the impact of systematic or non-normal error structures. We discuss these approaches and provide an overview of the error handling features implemented in iTOUGH2.
Date: December 1, 2010
Creator: Finsterle, S. & Zhang, Y.
Partner: UNT Libraries Government Documents Department

iTOUGH2: From parameter estimation to model structure identification

Description: iTOUGH2 provides inverse modeling capabilities for the TOUGH2 family of nonisothermal multiphase flow simulators. It can be used for a formalized sensitivity analysis, parameter estimation by automatic model calibration, and uncertainty propagation analyses. While iTOUGH2 has been successfully applied for the estimation of a variety of parameters based on different data types, it is recognized that errors in the conceptual model have a great impact on both the estimated parameters and the subsequent model predictions. Identification of the most suitable model structure is therefore one of the most important and most difficult tasks. Within the iTOUGH2 framework, model identification can be partly addressed through appropriate parameterization of alternative conceptual-model elements. In addition, statistical measures are provided that help rank the performance of different conceptual models. We present a number of features added to the code that allow for a better parameterization of conceptual model elements, specifically heterogeneity. We discuss how these new features can be used to support the identification of key model structure elements and their impact on model predictions.
Date: May 12, 2003
Creator: Finsterle, Stefan
Partner: UNT Libraries Government Documents Department

Massively Parallel Direct Simulation of Multiphase Flow

Description: The authors understanding of multiphase physics and the associated predictive capability for multi-phase systems are severely limited by current continuum modeling methods and experimental approaches. This research will deliver an unprecedented modeling capability to directly simulate three-dimensional multi-phase systems at the particle-scale. The model solves the fully coupled equations of motion governing the fluid phase and the individual particles comprising the solid phase using a newly discovered, highly efficient coupled numerical method based on the discrete-element method and the Lattice-Boltzmann method. A massively parallel implementation will enable the solution of large, physically realistic systems.
Date: August 10, 2000
Partner: UNT Libraries Government Documents Department

First Assessment of Computations of Turbulent Bubbly Flow and Particulate Flow with the COMMIX-M Program

Description: The COMMIX-M computer code, which describes steady-state and transient single- and multi-component flows in engineering systems, has been implemented to simulate suspension flows in laminar regimes and turbulent and bubbly particulate flows. This report presents a synopsis of the present code's capabilities, with particular emphasis on the recent development of turbulence models, and explains in detail the modifications necessary to simulate particulate flows and bubbly flows. First results of computations of turbulent bubbly and particulate flows are then given and compared with results of computations reported in the literature and with preliminary experimental results obtained at the Kernforschungszentrum Karlsruhe (Germany).
Date: May 1994
Creator: Bottoni, M.; Chang, F. C. & Ding, J.
Partner: UNT Libraries Government Documents Department

On the Inclusion of the Interfacial Area Between Phases in the Physical and Mathematical Description of Subsurface Multiphase Flow

Description: The scientific motivation for conducting this research lies in an assessment of the current state of modeling in the subsurface, where ''modeling'' refers to any systematic framework used to gain understanding of a system. At present, subsurface modeling addresses only the phases present, and even there considers the modeling process to be an extension of single phase flow. The shortcoming of this approach is that the governing flow equations do not account for some of the important physical phenomena. therefore accurate simulation is more of an art that a scientific exercise. Experimental and field programs designed to measure data in support of these equations may actually be seeking curve fitting coefficients rather than information characteristic of physical phenomena. By providing a more general framework, we can contribute to improving the knowledge base related to important processes in the subsurface.
Date: March 17, 2000
Creator: Gray, William G.; Soll, Wendy E. & Tompson, Andrew F.B.
Partner: UNT Libraries Government Documents Department

Multiphase flow in complex fracture apertures under a wide range of flow conditions

Description: The primary purpose of this project is to use a combination of computer modeling and laboratory experiments to obtain a better understanding of multiphase flow in geometrically complex fracture apertures under a wide range of flow conditions. Because traditional grid-based numeral methods perform poorly for multiphase flows with complex dynamic interfaces due to problems such as artificial interface broadening and grid entanglement, the modeling component of the program relies on particle based methods. In particle based models, the fluid-fluid interfaces move as the particles representing the fluids move--there is no need for explicit interface tracking, and no artificial front broadening. Because, different model approaches have characteristic strengths and weaknesses three different classes of particle-based models (lattice Boltzmann, dissipative particle dynamics and smoothed particle hydrodynamics) will be employed in this program. This will allow us to achieve our objective of simulating multiphase flow under a wide range of flow conditions for a wide range of fluid properties.
Date: June 1, 2003
Creator: Meakin, Paul; McCrerry, Glenn E. & McCligot, Donald
Partner: UNT Libraries Government Documents Department