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  • Fischer, Thomas  (15)
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  • 1
    Language: English
    In: Environmental Earth Sciences, 2013, Vol.69(2), pp.469-477
    Description: Over the course of hydrological research projects often a large number of heterogeneous data sets are acquired from sources as diverse as boreholes, gauging stations or satellite imagery. This data then need to be integrated into models for the simulation of hydrological processes. We propose a framework for exploration of geoscientific data and visually guided preparation of such models. Data sets from a large number of sources can be imported, combined and validated to avoid potential problems due to artefacts or inconsistencies between data sets in a subsequent simulation. Boundary conditions and domain discretisations for surface and subsurface models can be created and tested regarding criteria indicating possible numerical instabilities. All data sets including simulation results can be integrated into a user-controlled 3D scene and aspects of the data can be enhanced using a number of established visualisation techniques including thresholding and user-defined transfer functions. We present the application of this framework for the preparation of a model for simulation of groundwater flow in a river catchment in southwest Germany investigated in the scope of the WESS project.
    Keywords: Data exploration ; Hydrology ; Simulation ; Visualisation ; OpenGeoSys
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 2
    Language: English
    In: Environmental Earth Sciences, 2013, Vol.69(2), pp.617-631
    Description: In order to understand the groundwater dynamics and to improve the management of water resources in the Federal District of Brazil, this research proposes a 3D groundwater flow model to represent the groundwater level and flow system. The selected test site was the Pipiripau catchment. The development of the model was based on available geological, hydrogeological, geomorphological, climatological and pedological data. Geological and hydrogeological data were used to generate the 3D groundwater flow model. The 3D mesh elements of the domain were generated through the Groundwater Modeling System software, based on the logs of the well materials. The numerical simulation of the finite element method was implemented in the framework of the scientific software OpenGeoSys. With the 3D mesh-appropriated boundary conditions, annual average infiltration data and hydrogeological parameters were incorporated. Afterwards, the steady-state model was calibrated by the PEST software using available data of the water level from wells. The results showed the distribution of the steady-state hydraulic heads in the model domain, where the highest values occurred in the east and west recharge areas and the lowest values were found in the southwest of the basin. The results of this study can be a used as initial condition for the transient groundwater flow simulation and to provide a scientific basis for water resource management.
    Keywords: Pipiripau catchment ; Groundwater ; Modelling ; Water resource management
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 3
    Language: English
    In: Environmental Earth Sciences, 2015, Vol.73(5), pp.2269-2285
    Description: In past decades, high performance computing has became a valuable tool in many fields of environmental science and technology to utilize computational power for better characterization of the complexity of environmental systems as well as predicting their evolution in time. In this work, a parallel computing technique is presented for the numerical simulation of two-phase flow processes in porous media. The Galerkin finite element method (FEM) is used to solve the initial boundary value problem arising from the underlying mathematical model. The PETSc package is utilized for parallelization of the computational task in both the global assembly of the system of linear equations and the linear solver. In order to parallelize the global assembly of the linear equation system, the overlapping domain decomposition method is used. The preset parallel FEM approach is realized within the framework of OpenGeoSys, an open source C++ finite element code for numerical simulation of thermal, hydraulic, mechanical and chemical processes in fractured porous media. The computational efficiency of the approach has been tested with three examples of increasing complexity, the five spot benchmark, dense non-aquaeous phase liquid infiltration into a inhomogeneous porous medium and a real-world application to the $$\mathrm {CO}_2$$ CO 2 storage research site: Ketzin, in Germany.
    Keywords: Parallel computing ; Two-phase flow ; Porous medium ; Finite element method ; OpenGeoSys ; PETSc
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 4
    Language: English
    Description: This tutorial on the application of the open-source software OpenGeoSys (OGS) in computational hydrology is based on a one-week training course at the Helmholtz Centre...
    Keywords: Earth Sciences -- Hydrogeology; Earth Sciences -- Quantitative Geology; Earth Sciences -- Simulation and Modeling
    ISBN: 978-3-319-13334-8
    ISBN: 3319133349
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  • 5
    Language: English
    In: Geoscientific Model Development Discussions, 09/22/2017, pp.1-28
    Description: Most of the current large scale hydrological models do not contain a physically-based groundwater flow component. The main difficulties in large-scale groundwater modeling include the efficient representation of unsaturated zone flow, the characterization of dynamic groundwater-surface water interaction and the numerical stability while preserving complex physical processes and high resolution. To address these problems, we propose a highly-scalable coupled hydrologic and groundwater model (mHM#OGS) based on the integration of two open-source modeling codes: the mesoscale hydrologic Model (mHM) and the finite element simulator OpenGeoSys (OGS). mHM#OGS is coupled using a boundary condition-based coupling scheme that dynamically links the surface and subsurface parts. Nested time stepping allows smaller time steps for typically faster surface runoff routing in mHM and larger time steps for slower subsurface flow in OGS. mHM#OGS features the coupling interface which can transfer the groundwater recharge and river baseflow rate between mHM and OpenGeoSys. Verification of the coupled model was conducted using the time-series of observed streamflow and groundwater levels. Moreover, we force the transient model using groundwater recharge in two scenarios: (1) spatially variable recharge based on the mHM simulations, and (2) spatially homogeneous groundwater recharge. The modeling result in first scenario has a slightly higher correlation with groundwater head time-series, which further validates the plausibility of spatial groundwater recharge distribution calculated by mHM in the mesocale. The statistical analysis of model predictions shows a promising prediction ability of the model. The offline coupling method implemented here can reproduce reasonable groundwater head time series while keep a desired level of detail in the subsurface model structure with little surplus in computational cost. Our exemplary calculations show that the coupled model mHM#OGS can be a valuable tool to assess the effects of variability in land surface heterogeneity, meteorological, topographical forces and geological zonation on the groundwater flow dynamics.
    Keywords: Geology;
    ISSN: Geoscientific Model Development Discussions
    E-ISSN: 1991-962X
    Source: CrossRef
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  • 6
    Language: English
    In: Geoscientific Model Development, June 1, 2018, Vol.11(5), p.1989
    Description: Most large-scale hydrologic models fall short in reproducing groundwater head dynamics and simulating transport process due to their oversimplified representation of groundwater flow. In this study, we aim to extend the applicability of the mesoscale Hydrologic Model (mHM v5.7) to subsurface hydrology by coupling it with the porous media simulator OpenGeoSys (OGS). The two models are one-way coupled through model interfaces GIS2FEM and RIV2FEM, by which the grid-based fluxes of groundwater recharge and the river-groundwater exchange generated by mHM are converted to fixed-flux boundary conditions of the groundwater model OGS. Specifically, the grid-based vertical reservoirs in mHM are completely preserved for the estimation of land-surface fluxes, while OGS acts as a plug-in to the original mHM modeling framework for groundwater flow and transport modeling. The applicability of the coupled model (mHM-OGS v1.0) is evaluated by a case study in the central European mesoscale river basin - N#xE4;gelstedt. Different time steps, i.e., daily in mHM and monthly in OGS, are used to account for fast surface flow and slow groundwater flow. Model calibration is conducted following a two-step procedure using discharge for mHM and long-term mean of groundwater head measurements for OGS. Based on the model summary statistics, namely the Nash-Sutcliffe model efficiency (NSE), the mean absolute error (MAE), and the interquartile range error (QRE), the coupled model is able to satisfactorily represent the dynamics of discharge and groundwater heads at several locations across the study basin. Our exemplary calculations show that the one-way coupled model can take advantage of the spatially explicit modeling capabilities of surface and groundwater hydrologic models and provide an adequate representation of the spatiotemporal behaviors of groundwater storage and heads, thus making it a valuable tool for addressing water resources and management problems.
    Keywords: Water Resource Management – Case Studies ; Water Resource Management – Analysis ; Water Resource Management – Models ; Rivers – Case Studies ; Rivers – Analysis ; Rivers – Models ; Groundwater Flow – Case Studies ; Groundwater Flow – Analysis ; Groundwater Flow – Models ; Water Resources – Case Studies ; Water Resources – Analysis ; Water Resources – Models ; Groundwater – Case Studies ; Groundwater – Analysis ; Groundwater – Models ; Hydrology – Case Studies ; Hydrology – Analysis ; Hydrology – Models
    ISSN: 1991-959X
    ISSN: 19919603
    E-ISSN: 19919603
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  • 7
    Language: English
    In: Environmental Earth Sciences, 2013, Vol.69(2), pp.571-585
    Description: Water is scarce in the semi-arid to arid regions around the Dead Sea, where water supply mostly relies on restricted groundwater resources. Due to increasing population in this region, the regional aquifer system is exposed to additional stress. This results in the continuous decrease in water level of the adjacent Dead Sea. The interaction of an increasing demand for water due to population growth and the decrease of groundwater resources will intensify in the near future. Thus, the water supply situation could worsen significantly unless sustainable water resource management is conducted. In this study, we develop a regional groundwater flow model of the eastern and southern Judea Group Aquifer to investigate the groundwater regime in the western Dead Sea drainage basin of Israel and the West Bank. An extensive geological database was developed and consequently a high-resolution structural model was derived. This structural model was the basis for various groundwater flow scenarios. The objective was to capture the spatial heterogeneity of the aquifer system and to apply these results to the southern part of the study area, which has not been studied in detail until now. As a result we analyzed quantitatively the flow regime, the groundwater mass balance and the hydraulic characteristics (hydraulic conductivity and hydraulic head) of the cretaceous aquifer system and calibrated them with PEST. The calibrated groundwater flow model can be used for integrated groundwater water management purposes in the Dead Sea area, especially within the framework of the SUMAR-Project.
    Keywords: Numerical groundwater flow modelling ; Structural model ; 3-D groundwater flow model ; Model calibration ; OpenGeoSys ; Dead Sea ; Semi-arid and arid regions ; SUMAR
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 8
    Language: English
    In: Energy Procedia, September 2017, Vol.125, pp.310-317
    Description: We propose a new benchmark for the simulation of thermal convection in a 3D faulted system. Linear stability analysis is adopted to estimate the critical viscous-dependent Rayleigh number. These results are used to quantify the reliability of OpenGeoSys-5, Golem and FEFLOW simulators in accounting for the onset conditions and in predicting the long-term behavior of convective flow patterns. By comparing the analytical and numerical results, we can conclude that the proposed methodology and Rayleigh expressions can be applied as benchmark case for any numerical study involving coupled hydrothermal fluid flow in fault zones.
    Keywords: Fault ; Convection ; Rayleigh ; Simulation ; Opengeosys ; Moose ; Engineering ; Economics
    ISSN: 1876-6102
    E-ISSN: 1876-6102
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  • 9
    Language: English
    In: Environmental Earth Sciences, Nov, 2014, Vol.72(10), p.3881(19)
    Description: Byline: Lars Bilke (1), Thomas Fischer (1), Carolin Helbig (1), Charlotte Krawczyk (9), Thomas Nagel (1), Dmitri Naumov (7), Sebastian Paulick (4), Karsten Rink (1), Agnes Sachse (2), Sophie Schelenz (3), Marc Walther (6), Norihiro Watanabe (1), Bjorn Zehner (8), Jennifer Ziesch (9), Olaf Kolditz (1,5) Keywords: Virtual reality; Visualization; Computer graphics; Data exploration; Hydrological processes; Geotechnics; Seismic data; OpenGeoSys; VISLAB Abstract: Scientific visualization is an integral part of the modeling workflow, enabling researchers to understand complex or large data sets and simulation results. A high-resolution stereoscopic virtual reality (VR) environment further enhances the possibilities of visualization. Such an environment also allows collaboration in work groups including people of different backgrounds and to present results of research projects to stakeholders or the public. The requirements for the computing equipment driving the VR environment demand specialized software applications which can be run in a parallel fashion on a set of interconnected machines. Another challenge is to devise a useful data workflow from source data sets onto the display system. Therefore, we develop software applications like the OpenGeoSys Data Explorer, custom data conversion tools for established visualization packages such as ParaView and Visualization Toolkit as well as presentation and interaction techniques for 3D applications like Unity. We demonstrate our workflow by presenting visualization results for case studies from a broad range of applications. An outlook on how visualization techniques can be deeply integrated into the simulation process is given and future technical improvements such as a simplified hardware setup are outlined. Author Affiliation: (1) Department of Environmental Informatics, Helmholtz Centre for Environmental Research, Leipzig, Germany (2) Department of Catchment Hydrology, Helmholtz Centre for Environmental Research, Leipzig, Germany (3) Department of Monitoring and Exploration Technologies, Helmholtz Centre for Environmental Research, Leipzig, Germany (4) Department of Ecologial Modelling, Helmholtz Centre for Environmental Research, Leipzig, Germany (5) Chair of Applied Environmental System Analysis, Technische University at Dresden, Dresden, Germany (6) Institute for Groundwater Management, Technische University at Dresden, Dresden, Germany (7) Faculty of Mechanical and Energy Engineering, Leipzig University of Applied Sciences, Leipzig, Germany (8) Federal Institute for Geosciences and Natural Resources, Berlin, Germany (9) Leibniz Institute for Applied Geophysics, Hannover, Germany Article History: Registration Date: 07/10/2014 Received Date: 25/08/2014 Accepted Date: 06/10/2014 Online Date: 19/10/2014
    Keywords: Visualization (Computer) -- Case Studies ; Engineering Geology -- Case Studies ; Hydrology -- Case Studies ; Workflow Software -- Case Studies ; Graphics Software -- Case Studies
    ISSN: 1866-6280
    Source: Cengage Learning, Inc.
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  • 10
    Language: English
    In: Environmental Earth Sciences, 2014, Vol.72(10), pp.3881-3899
    Description: Scientific visualization is an integral part of the modeling workflow, enabling researchers to understand complex or large data sets and simulation results. A high-resolution stereoscopic virtual reality (VR) environment further enhances the possibilities of visualization. Such an environment also allows collaboration in work groups including people of different backgrounds and to present results of research projects to stakeholders or the public. The requirements for the computing equipment driving the VR environment demand specialized software applications which can be run in a parallel fashion on a set of interconnected machines. Another challenge is to devise a useful data workflow from source data sets onto the display system. Therefore, we develop software applications like the OpenGeoSys Data Explorer, custom data conversion tools for established visualization packages such as ParaView and Visualization Toolkit as well as presentation and interaction techniques for 3D applications like Unity. We demonstrate our workflow by presenting visualization results for case studies from a broad range of applications. An outlook on how visualization techniques can be deeply integrated into the simulation process is given and future technical improvements such as a simplified hardware setup are outlined.
    Keywords: Virtual reality ; Visualization ; Computer graphics ; Data exploration ; Hydrological processes ; Geotechnics ; Seismic data ; OpenGeoSys ; VISLAB
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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