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  • SpringerLink  (55)
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  • 1
    Language: English
    In: Environmental Earth Sciences, 2012, Vol.67(6), pp.1859-1859
    Description: Byline: Olaf Kolditz (1,2), Karsten Rink (1), Haibing Shao (1), Thomas Kalbacher (1), Ralf Kunkel (3), Steffen Zacharias (1), Peter Dietrich (1,4) Author Affiliation: (1) Helmholtz Centre for Environmental Research-UFZ, Permoserstrasse 15, 04318, Leipzig, Germany (2) Applied Environmental Systems Analysis, Technische Universitat Dresden, 01062, Dresden, Germany (3) Forschungszentrum Juelich GmbH, 52425, Juelich, Germany (4) Environmental and Engineering Geophysics, Eberhard-Karls-University of Tubingen, Holderlinstrasse 12, 72074, Tubingen, Germany Article History: Registration Date: 27/08/2012 Online Date: 12/09/2012 Article note: The online version of the original article can be found under doi: 10.1007/s12665-012-1661-8. The online version of the original article can be found at http://dx.doi.org/10.1007/s12665-012-1661-8.
    Keywords: Geophysics -- Models;
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 2
    Language: English
    In: Environmental Earth Sciences, 2012, Vol.66(4), pp.1279-1284
    Description: Byline: Olaf Kolditz (1,2), Karsten Rink (1), Haibing Shao (1), Thomas Kalbacher (1), Steffen Zacharias (1), Peter Dietrich (1,3) Author Affiliation: (1) Helmholtz Centre for Environmental Research-UFZ, Permoserstrasse 15, 04318, Leipzig, Germany (2) Applied Environmental Systems Analysis, Technische Universitat Dresden, 01062, Dresden, Germany (3) Environmental and Engineering Geophysics, Eberhard-Karls-University of Tubingen, Holderlinstrasse 12, 72074, Tubingen, Germany Article History: Registration Date: 27/03/2012 Online Date: 19/04/2012 Article note: A German-wide Earth observation network, TERENO, was launched 3 years ago by the Helmholtz Association and now brings together climate and environmental research from the Alps to the Baltic coast. UFZ researchers from the Department of Environmental Informatics, Karsten Rink, Haibing Shao, Thomas Kalbacher, and Olaf Kolditz together with colleagues from the Department of Monitoring and Exploration Technologies, Steffen Zacharias and Peter Dietrich outline how their collaborative work embarks on new paths with this long-term environmental observation system. Dr. Olaf Kolditz heads UFZ's Department of Environmental Informatics and chairs the Department of Applied Environmental Systems Analysis at Technical University of Dresden. Dr. Peter Dietrich heads UFZ's Department of Monitoring und Exploration Technologies and is also the Professor for Environmental and Engineering Geophysics at the Eberhard-Karls-University of Tubingen.
    Keywords: Geophysics;
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 3
    Language: English
    In: Environmental Earth Sciences, 2015, Vol.74(10), pp.7147-7158
    Description: This paper presents the design and integration of a GIS-based data model for the regional hydrologic simulation in the Meijiang watershed, China. Hydrologic systems (HS) require integration of data and models simulating different processes. Here, an object-oriented approach using Unified Modeling Language (UML) is introduced, which supports the development of GIS-based Geodatabase model—GeoHydro/DataBase (GH/DB). Spatial data, such as basins, stream network, and observation stations are stored in the feature classes. The time series and their attributes are included in the tables. Relationship classes are used to link associated objects. The new development within the scientific program OpenGeoSys (OGS) is the integration of GH/DB into the numerical simulations. The graphical user interface is implemented for the pre- and post-processing of the simulation. As for the case study, a regional hydrologic model is developed in the Meijiang watershed area for the understanding of water infiltration from surface into groundwater via soil layer with various time scales. The integration of databases and modeling tool represents the comprehensive hydrosystems and thus it is a useful tool to understand the different processes and interactions between the related hydrological compartments.
    Keywords: Geographical information system (GIS) ; Unified modeling language (UML) ; GeoHydro/DataBase (GH/DB) ; Hydrologic simulation ; Meijiang watershed ; OpenGeoSys
    ISSN: 1866-6280
    E-ISSN: 1866-6299
    Source: Springer Science & Business Media B.V.
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  • 4
    Language: English
    In: Environmental Earth Sciences, 2013, Vol.70(7), pp.3363-3380
    Description: As part of the HG-A experiment in the Mont Terri Rock Laboratory, large-scale in situ water/gas injection experiments was conducted in a microtunnel. This research work focuses on the numerical analysis of the experimental data and the in situ observations. Concerning a temporary change of the hydromechanical properties of Opalinus Clay during experimental operations, three phases were numerically interpreted. These included the generation of excavation damaged zone during tunnel excavation, in which highly permeable flow paths around the tunnel have been formed; the self-sealing effect during water tests; and the pressure evolution during a long-term gas injection test. A coupled two-phase flow and mechanics model, taking into account the strong anisotropic properties of Opalinus Clay, was developed to interpret the measured data. The hydraulic anisotropy was described by a transversely isotropic permeability tensor. An elasto-plastic model was established to consider both stiffness anisotropy and strength anisotropy. Anisotropic plasticity was studied using the microstructure tensor method.
    Keywords: HM coupling ; Anisotropy ; In situ injection experiment ; Mont Terri Rock Laboratory ; EDZ
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 5
    Language: English
    In: Environmental Earth Sciences, 2012, Vol.67(2), pp.613-632
    Description: The idea of this paper is twofold. On one hand, we propose a general systematic for benchmarking of CO 2 modelling. On the other hand, we integrate material from the CLEAN project into this framework to demonstrate its applicability (Kühn et al. in Environ Earth Sci, this issue 2011). Benchmarks are an important instrument to gain a better understanding of interacting physico-chemical processes and they are a necessary tool to verify the algorithms and the software dedicated to simulate the separated and differently coupled thermo-hydro-mechanical/chemical processes during injecting and storing CO 2 in the subsurface. In general we distinguish between process- and site-related test cases. Process-related benchmarks deal with the required complexity of process coupling as well as equations of state for fluids and constitutive laws for geologic formations. Site-specific benchmarks represent different geological settings for potential CO 2 reservoirs, e.g., depleted gas and oil reservoirs as well as deep saline aquifers. The data basis for benchmarking mainly comes from experimental work in the CLEAN project as well as from literature. The benchmarking systematic is aimed at serving as basis for process studies, experimental design as well as for code inter-comparison purposes not only for numerical tools having used by the CLEAN partners but also for upcoming international benchmarking initiatives as well.
    Keywords: CLEAN ; CO2BENCH ; Benchmarking ; CO modelling ; OpenGeoSys ; Depleted gas reservoirs ; Deep saline aquifers ; Natural analogues
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 6
    Language: English
    In: Environmental Earth Sciences, 2014, Vol.72(10), pp.3857-3868
    Description: We present a framework that allows users to apply a number of strategies to view and modify a wide range of environmental data sets for the modelling of natural phenomena. These data sets can be concurrently visualised to find inconsistencies or artefacts. This ensures at an early stage that models set up for the simulation of hydrological or thermal processes will not give implausible results due to complications based on input data. A number of generally applicable visualisation techniques are provided by our framework to help researchers detect potential problems. We also propose a number of mapping algorithms for the integration of multiple data sets to resolve some of the most common issues. Techniques for the presentation of input- and modelling data in combination with simulation results are proposed with respect to the benefits of visualisation of environmental data within specialised environments. The complete workflow from input data to presentation is demonstrated based on a case study in Central Germany. We identify typical problems, propose approaches for a suitable data integration for this case study and compare results of the original and modified data sets.
    Keywords: Computer graphics ; Visualisation ; Virtual reality ; Hydrology ; OpenGeoSys Data Explorer
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 7
    Language: English
    In: Environmental Earth Sciences, 2014, Vol.72(10), pp.3795-3802
    Description: Current visualization techniques for computational fluid dynamics applications are sophisticated and work well in simple geometries. For complex geometries such as pore spaces, multiple domain boundaries obstruct the view and make the studying of fluid flow fields difficult. To overcome these deficiencies, we use two-sided materials to render the domain boundaries. Using this technique, it is possible to place the camera inside the domain and have a non-obstructed view of the surrounding flow field without losing spatial reference to the domain boundaries. As a result, a larger part of fluid flow visualization is visible. Two-sided material rendering was successfully applied to display still images with Blender Cycles renderer, in a virtual reality environment, and several implementation techniques were explored for using the Visualization Toolkit.
    Keywords: 3D Graphics ; Virtual reality ; Image generation ; VTK ; OpenGL ; VISLab TESSIN
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 8
    Language: English
    In: Transport in Porous Media, 2011, Vol.90(2), pp.545-573
    Description: Predicting fluid replacement by two-phase flow in heterogeneous porous media is of importance for issues such as supercritical CO 2 sequestration, the integrity of caprocks and the operation of oil water/brine systems. When considering coupled process modelling, the location of the interface is of importance as most of the significant interaction between processes will be happening there. Modelling two-phase flow using grid based techniques presents a problem as the fluid–fluid interface location is approximated across the scale of the discretisation. Adaptive grid methods allow the discretisation to follow the interface through the model, but are computationally expensive and make coupling to other processes (thermal, mechanical and chemical) complicated due to the constant alteration in grid size and effects thereof. Interface tracking methods have been developed that apply sophisticated reconstruction algorithms based on either the ratio of volumes of a fluid in an element (Volume of Fluid Methods) or the advective velocity of the interface throughout the modelling regime (Level set method). In this article, we present an “Analytical Front Tracking” method where a generic analytical solution for two-phase flow is used to “add information” to a finite element model. The location of the front within individual geometrical elements is predicted using the saturation values in the elements and the velocity field of the element. This removes the necessity for grid adaptation, and reduces the need for assumptions as to the shape of the interface as this is predicted by the analytical solution. The method is verified against a standard benchmark solution and then applied to the case of CO 2 pooling and forcing its way into a heterogeneous caprock, replacing hot brine and eventually breaking through. Finally the method is applied to simulate supercritical CO 2 injected into a brine saturated heterogeneous reservoir rock leading to significant viscous fingering and developement of preferential flow paths. The results are compared with to a finite volume simulation.
    Keywords: Two-phase flow ; Hybrid analytical numerical ; CO sequestration ; Caprock integrity ; Front tracking
    ISSN: 0169-3913
    E-ISSN: 1573-1634
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  • 9
    Language: English
    In: Environmental Earth Sciences, 2011, Vol.64(5), pp.1323-1333
    Description: Water shortage and groundwater pollution have become two primary environmental concerns to Beijing since the 1990s. The local aquifers, as the dominant sources for domestic and agricultural water supply, are depleting due to groundwater abstraction and continuous drought in recent years with rapid urbanization and increasing water consumption. Therefore, understanding the hydrogeological system is fundamental for a sustainable water resources management. In this article, the numerical analysis of a 3-D regional groundwater flow model for the Nankou area is presented. The hydrogeological system is reproduced according to sparsely distributed boreholes data. The numerical analysis is carried out using the scientific software OpenGeoSys, which is based on the finite element method. The model calibration and sensitivity analysis are accomplished with inverse methods by applying a model independent parameter estimation system (PEST). The results of the calibrated model show reasonable agreements with observed water levels. The transient groundwater flow simulations reflect the observed drawdown of the last 9 years and show the formation of a depression cone in an intensively pumped area.
    Keywords: Groundwater modeling ; OpenGeoSys ; PEST ; Nankou
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 10
    Language: English
    In: Environmental Earth Sciences, 2011, Vol.62(6), pp.1197-1207
    Description: The present work compares the performance of two alternative flow models for the simulation of thermal-hydraulic coupled processes in low permeable porous media: non-isothermal Richards’ and two-phase flow concepts. Both models take vaporization processes into account: however, the Richards’ model neglects dynamic pressure variations and bulk flow of the gaseous phase. For the comparison of the two approaches first published, data from a laboratory experiment are studied involving thermally driven moisture flow in a partially saturated bentonite sample. Then a benchmark test of longer-term thermal-hydraulic behavior in the engineered barrier system of a geological nuclear waste repository is analyzed (DECOVALEX project). It was found that both models can be used to reproduce the vaporization process if the intrinsic permeability is relative high. However, when a thermal-hydraulic coupled problem has the same low intrinsic permeability, only the two-phase flow approach provides reasonable results.
    Keywords: Non-isothermal two-phase flow ; Richards’ approximation ; Porous media ; CTF1 experiment ; DECOVALEX task D
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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