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We present a sequence of purely advective transport models that demonstrate the influence of small-scale geometric inhomogeneities on contaminant transport in fractured crystalline rock. Special weight is placed on the role of statistically generated variable fracture apertures. The fracture network geometry and the aperture distribution are based on information from an in situ radionuclide retardation experiment performed at Grimsel test site (Swiss Alps). The obtained breakthrough curves are fitted with the advection dispersion equation and continuous-time random walks (CTRW). CTRW is found to provide superior fits to the late-arrival tailing and is also found to show a good correlation with the velocity distributions obtained from the hydraulic models. The impact of small-scale heterogeneities, both in fracture geometry and aperture, on transport is shown to be considerable. 相似文献
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Haibing Shao Svitlana V. Dmytrieva Olaf Kolditz Dmitrii A. Kulik Wilfried Pfingsten Georg Kosakowski 《Applied Geochemistry》2009
The numerical simulation of reactive mass transport processes in complex geochemical environments is an important tool for the performance assessment of future waste repositories. A new combination of the multi-component mass transport code GeoSys/RockFlow and the Gibbs Energy Minimization (GEM) equilibrium solver GEM-Selektor is used to calculate the accurate equilibrium of multiple non-ideal solid solutions which are important for the immobilization of radionuclides such as Ra. The coupled code is verified by a widely used benchmark of dissolution–precipitation in a calcite–dolomite system. A more complex application shown in this paper is the transport of Ra in the near-field of a nuclear waste repository. Depending on the initial inventories of Sr, Ba and sulfate, non-ideal sulfate and carbonate solid solutions can fix mobile Ra cations. Due to the complex geochemical interactions, the reactive transport simulations can describe the migration of Ra in a much more realistic way than using the traditional linear KD approach only. 相似文献
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Kosakowski Paweł Kotarba Maciej J. Piestrzyński Adam Shogenova Alla Więcław Dariusz 《International Journal of Earth Sciences》2017,106(2):743-761
International Journal of Earth Sciences - We present geochemical characteristics of the Lower Palaeozoic shales deposited in the Baltic Basin and Podlasie Depression. In the study area, this strata... 相似文献
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Hybrid analytical and finite element numerical modeling of mass and heat transport in fractured rocks with matrix diffusion 总被引：1，自引：0，他引：1
Christopher I. McDermott Robert Walsh Ralph Mettier Georg Kosakowski Olaf Kolditz 《Computational Geosciences》2009,13(3):349-361
Quantification of mass and heat transport in fractured porous rocks is important to areas such as contaminant transport, storage
and release in fractured rock aquifers, the migration and sorption of radioactive nuclides from waste depositories, and the
characterization of engineered heat exchangers in the context of enhanced geothermal systems. The large difference between
flow and transport characteristics in fractures and in the surrounding matrix rock means models of such systems are forced
to make a number of simplifications. Analytical approaches assume a homogeneous system, numerical approaches address the scale
at which a process is operating, but may lose individual important processes due to averaging considerations. Numerical stability
criteria limit the contrasts possible in defining material properties. Here, a hybrid analytical–numerical method for transport
modeling in fractured media is presented. This method combines a numerical model for flow and transport in a heterogeneous
fracture and an analytical solution for matrix diffusion. By linking the two types of model, the advantages of both methods
can be combined. The methodology as well as the mathematical background are developed, verified for simple geometries, and
applied to fractures representing experimental field conditions in the Grimsel rock laboratory. 相似文献
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Geometric modelling and object-oriented software concepts applied to a heterogeneous fractured network from the Grimsel rock laboratory 总被引：2，自引：0，他引：2
Thomas Kalbacher Ralph Mettier Chris McDermott Wenqing Wang Georg Kosakowski Takeo Taniguchi Olaf Kolditz 《Computational Geosciences》2007,11(1):9-26
Discrete fracture network simulations are computationally intensive and usually time-consuming to construct and configure.
This paper presents a case study with techniques for building a 3D finite element model of an inhomogeneous fracture network
for modelling flow and tracer transport, combining deterministic and stochastic information on fracture aperture distributions.
The complex intersected fractures represent a challenge for geometrical model design, mesh quality requirements and property
allocations. For the integrated and holistic modelling approach, including the application of numerical and analytical simulation
techniques, new object-oriented concepts in software engineering are implemented to ensure a resourceful and practicable software
environment. 相似文献
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Ferdinand F. Hingerl Georg Kosakowski Thomas Wagner Dmitrii A. Kulik Thomas Driesner 《Computational Geosciences》2014,18(2):227-242
GEMSFIT, a parallelized open-source tool for fitting thermodynamic activity models has been developed. It is the first open-source implementation of a generic geochemical-thermodynamic fitting tool coupled to a chemical equilibrium solver which uses the direct Gibbs energy minimization (GEM) approach. This enables speciation-based fitting of complex solution systems such as solid solutions and mixed solvents. The extendable framework of GEMSFIT provides a generic interface for fitting geochemical activity models at varying system compositions, temperatures and pressures. GEMSFIT provides the most common tools for statistical analysis which allow thorough evaluation of the fitted parameters. The program can receive input of measured data from a PostgreSQL database server or exported spreadsheets. The fitting tool allows for bound, linear, and nonlinear (in)equality-constrained minimization of weighted squared residuals of highly nonlinear systems over a wide temperature and pressure interval only limited by user-supplied thermodynamic data. Results from parameter regression as well as from statistical analysis can be visualized and directly printed to various graphical formats. Efficient use of the code is facilitated by a graphical user interface which assists in setting up GEMSFIT input files. The usage and resulting output of GEMSFIT is demonstrated by results from parameter regression of the extended universal quasichemical aqueous activity model for geothermal brines. 相似文献
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Dmitrii A. Kulik Thomas Wagner Svitlana V. Dmytrieva Georg Kosakowski Ferdinand F. Hingerl Konstantin V. Chudnenko Urs R. Berner 《Computational Geosciences》2013,17(1):1-24
Reactive mass transport (RMT) simulation is a powerful numerical tool to advance our understanding of complex geochemical processes and their feedbacks in relevant subsurface systems. Thermodynamic equilibrium defines the baseline for solubility, chemical kinetics, and RMT in general. Efficient RMT simulations can be based on the operator-splitting approach, where the solver of chemical equilibria is called by the mass transport part for each control volume whose composition, temperature, or pressure has changed. Modeling of complex natural systems requires consideration of multiphase–multicomponent geochemical models that include nonideal solutions (aqueous electrolytes, fluids, gases, solid solutions, and melts). Direct Gibbs energy minimization (GEM) methods have numerous advantages for the realistic geochemical modeling of such fluid–rock systems. Substantial improvements and extensions to the revised GEM interior point method algorithm based on Karpov’s convex programming approach are described, as implemented in the GEMS3K C/C+?+ code, which is also the numerical kernel of GEM-Selektor v.3 package (http://gems.web.psi.ch). GEMS3K is presented in the context of the essential criteria of chemical plausibility, robustness of results, mass balance accuracy, numerical stability, speed, and portability to high-performance computing systems. The stand-alone GEMS3K code can treat very complex chemical systems with many nonideal solution phases accurately. It is fast, delivering chemically plausible and accurate results with the same or better mass balance precision as that of conventional speciation codes. GEMS3K is already used in several coupled RMT codes (e.g., OpenGeoSys-GEMS) capable of high-performance computing. 相似文献
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Timothy J. Galvin Miroslav D. Filipović Nicholas F. H. Tothill Evan J. Crawford Andrew N. O’Brien Nicholas Seymour Thomas G. Pannuti Alekzander R. Kosakowski Biswas Sharma 《Astrophysics and Space Science》2014,353(2):603-611
We re-examine a series of archived centimetre radio-continuum observations (λ=16, 6 and 3 cm) focusing on NGC?7793 using the Australia Telescope Compact Array. These new images are both very sensitive (σ=0.011 mJy/beam) and feature reasonably high angular resolution (down to <3″). Using these images, a total of 76 discrete radio sources are identified, of which 57 have been classified. We also studied the radio component of the micro-quasar NGC7793-S26 which shows two distinct regions of somewhat steep spectral index (α) between ?0.3 and ?0.7. 相似文献
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