1,720,974 research outputs found
Bestimmung von hydraulischen Parametern in Lockergesteinen: Ein Vergleich unterschiedlicher Feldmethoden
No full textISSN:1432-1165ISSN:1430-483XISSN:1430-483
Investigation of hydraulic properties in fractured aquifers using cross-well travel-time based thermal tracer tomography: Numerical and field experiments
No full textCharacterization of aquifer heterogeneity by tomographic slug test responses considering wellbore effects
No full texthttp://dx.doi.org/10.13039/501100002855 Ministry of Science and Technology of the People's Republic of Chin
Hybrid Discrete Fracture Network Inversion of Hydraulic Tomography Data From a Fractured‐Porous Field Site
No full textAbstract
The accurate characterization of hydraulic conductivity heterogeneities in an aquifer is crucial for predicting flow and transport processes correctly. Hydraulic tomography (HT) experiments are often used to infer the hydraulically relevant features, but the correct inversion of the data remains a challenging task. We implemented a discrete fracture network (DFN) inversion approach that is expanded by considering a nonzero matrix permeability. The hybrid model allows the accurate characterization of fractured‐porous sites by taking into account both matrix and fracture flow. This novel inversion algorithm is successfully applied to HT data acquired at a field site in Goettingen (Germany), and the results are compared with those of a standard travel time inversion. Furthermore, we validate the inversion results by using them as the underlying material parameters for simulating heat tracer experiments and comparing the modeled temperature responses with those of heat tracer tests actually conducted at the site. It is shown that the DFN ensemble predicts the thermal response of the experiments correctly for the two major fractures in terms of location, amplitude, and time‐dependent behavior of the temperature anomaly, as long as the stochastic nature of the results is taken into account. We conclude that considering both matrix and fracture flow in a hybrid DFN inversion approach can lead to significant improvements in flow and transport modeling at fractured‐porous sites.Plain Language Summary
For understanding groundwater processes correctly, precise knowledge about the relevant geological structures in the subsurface is crucial. To infer this information, hydraulic tomography (HT) experiments are often used, which are based on sequential pumping tests in boreholes. The acquired data are usually processed by inversion techniques that allow for computing a subsurface model from the field observations. There are two different conceptual approaches: (a) continuum models, which assume a smooth distribution of the hydraulic parameters, and (b) discrete fracture network (DFN) models, which are based on an impermeable rock matrix, crossed by a limited number of fractures exclusively responsible for groundwater flow. However, certain sites show characteristics of both models, meaning that both the rock matrix and individual fractures are relevant. Therefore, we developed a new inversion technique (hybrid DFN inversion) that combines the two approaches. The method is tested on HT data acquired at a field site in Goettingen (Germany), and the results are validated against data from independent experiments (thermal tracer tests). It is shown that the subsurface models from the new hybrid DFN inversion are more accurate and reliable. We conclude that groundwater modeling at those sites can be improved significantly when using the new inversion method.Key Points
A novel inversion approach for hydraulic tomography (HT) data considering flow in both discrete fractures and porous matrix is introduced
The method is applied to HT data from a fractured‐porous field site in Göttingen (Germany)
The results are successfully validated against independent thermal tracer test dataAbstract
The accurate characterization of hydraulic conductivity heterogeneities in an aquifer is crucial for predicting flow and transport processes correctly. Hydraulic tomography (HT) experiments are often used to infer the hydraulically relevant features, but the correct inversion of the data remains a challenging task. We implemented a discrete fracture network (DFN) inversion approach that is expanded by considering a nonzero matrix permeability. The hybrid model allows the accurate characterization of fractured‐porous sites by taking into account both matrix and fracture flow. This novel inversion algorithm is successfully applied to HT data acquired at a field site in Goettingen (Germany), and the results are compared with those of a standard travel time inversion. Furthermore, we validate the inversion results by using them as the underlying material parameters for simulating heat tracer experiments and comparing the modeled temperature responses with those of heat tracer tests actually conducted at the site. It is shown that the DFN ensemble predicts the thermal response of the experiments correctly for the two major fractures in terms of location, amplitude, and time‐dependent behavior of the temperature anomaly, as long as the stochastic nature of the results is taken into account. We conclude that considering both matrix and fracture flow in a hybrid DFN inversion approach can lead to significant improvements in flow and transport modeling at fractured‐porous sites.Plain Language Summary
For understanding groundwater processes correctly, precise knowledge about the relevant geological structures in the subsurface is crucial. To infer this information, hydraulic tomography (HT) experiments are often used, which are based on sequential pumping tests in boreholes. The acquired data are usually processed by inversion techniques that allow for computing a subsurface model from the field observations. There are two different conceptual approaches: (a) continuum models, which assume a smooth distribution of the hydraulic parameters, and (b) discrete fracture network (DFN) models, which are based on an impermeable rock matrix, crossed by a limited number of fractures exclusively responsible for groundwater flow. However, certain sites show characteristics of both models, meaning that both the rock matrix and individual fractures are relevant. Therefore, we developed a new inversion technique (hybrid DFN inversion) that combines the two approaches. The method is tested on HT data acquired at a field site in Goettingen (Germany), and the results are validated against data from independent experiments (thermal tracer tests). It is shown that the subsurface models from the new hybrid DFN inversion are more accurate and reliable. We conclude that groundwater modeling at those sites can be improved significantly when using the new inversion method.Key Points
A novel inversion approach for hydraulic tomography (HT) data considering flow in both discrete fractures and porous matrix is introduced
The method is applied to HT data from a fractured‐porous field site in Göttingen (Germany)
The results are successfully validated against independent thermal tracer test dataAbstract
The accurate characterization of hydraulic conductivity heterogeneities in an aquifer is crucial for predicting flow and transport processes correctly. Hydraulic tomography (HT) experiments are often used to infer the hydraulically relevant features, but the correct inversion of the data remains a challenging task. We implemented a discrete fracture network (DFN) inversion approach that is expanded by considering a nonzero matrix permeability. The hybrid model allows the accurate characterization of fractured‐porous sites by taking into account both matrix and fracture flow. This novel inversion algorithm is successfully applied to HT data acquired at a field site in Goettingen (Germany), and the results are compared with those of a standard travel time inversion. Furthermore, we validate the inversion results by using them as the underlying material parameters for simulating heat tracer experiments and comparing the modeled temperature responses with those of heat tracer tests actually conducted at the site. It is shown that the DFN ensemble predicts the thermal response of the experiments correctly for the two major fractures in terms of location, amplitude, and time‐dependent behavior of the temperature anomaly, as long as the stochastic nature of the results is taken into account. We conclude that considering both matrix and fracture flow in a hybrid DFN inversion approach can lead to significant improvements in flow and transport modeling at fractured‐porous sites.Plain Language Summary
For understanding groundwater processes correctly, precise knowledge about the relevant geological structures in the subsurface is crucial. To infer this information, hydraulic tomography (HT) experiments are often used, which are based on sequential pumping tests in boreholes. The acquired data are usually processed by inversion techniques that allow for computing a subsurface model from the field observations. There are two different conceptual approaches: (a) continuum models, which assume a smooth distribution of the hydraulic parameters, and (b) discrete fracture network (DFN) models, which are based on an impermeable rock matrix, crossed by a limited number of fractures exclusively responsible for groundwater flow. However, certain sites show characteristics of both models, meaning that both the rock matrix and individual fractures are relevant. Therefore, we developed a new inversion technique (hybrid DFN inversion) that combines the two approaches. The method is tested on HT data acquired at a field site in Goettingen (Germany), and the results are validated against data from independent experiments (thermal tracer tests). It is shown that the subsurface models from the new hybrid DFN inversion are more accurate and reliable. We conclude that groundwater modeling at those sites can be improved significantly when using the new inversion method.Key Points
A novel inversion approach for hydraulic tomography (HT) data considering flow in both discrete fractures and porous matrix is introduced
The method is applied to HT data from a fractured‐porous field site in Göttingen (Germany)
The results are successfully validated against independent thermal tracer test dat
A Numerical Study of Slug Tests in a Three‐Dimensional Heterogeneous Porous Aquifer Considering Well Inertial Effects
No full textHydraulic Travel Time Diagnosis Using Recovery Data from Short-Term Pumping Tests for Rapid Aquifer Characterization: A Numerical Study with Monte-Carlo Simulations
No full textIn the realm of groundwater science, characterization of heterogeneous aquifers is pivotal for resolving diverse groundwater resource and engineering-related problems that require the detailed spatial distribution of hydraulic parameters. As research progresses, one hydraulic tomographical method, which is based on hydraulic travel time inversion, emerges as a promising and rapid method due to its robust and efficient calculation. In the field, the acquisition of hydraulic excitation and head observation data required for inversion is less time-consuming. Data collection from a single hydraulic test (such as a pumping test) typically takes only a few minutes or even a few tens of seconds. However, the field application of this method faces challenges. Hydraulic travel time is typically generated in the early stages of hydrogeological tests (e.g., early drawdown of a pumping test), yet accurate data may not be readily available because of the noise signals from test equipment, which can contaminate travel time signals, leading to inaccurate inversion results. A potential solution lies in utilizing the smooth head observation during the recovery period after the pump is turned off, which yields more accurate travel times for inversion calculations. In this paper, the mathematical development suggests that the travel time of the recovery phase aligns with that of the pumping phase when pumping reaches a steady or quasi-steady state. Subsequently, by employing Monte-Carlo simulations, 1200 realizations of two-dimensional heterogeneous confined aquifer models were generated for simulating pumping tests with different pumping durations. The calculated head data were then utilized to compute the travel time derived from drawdown data (t) and recovery data (t′), respectively. Comparisons showed that t is equal to t′ when drawdown reaches a steady or quasi-steady state. Conversely, when the pump is turned off before reaching a quasi-steady state, t differs from t′. However, results also indicate the fact that a decent hydraulic travel time diagnosis can be obtained, especially for the cases when travel times are smaller than 15 s. Given the statistical results of Monte-Carlo simulations, as well as experience during pumping tests in the field with different scenarios, using the recovery data from 60 s of pumping duration, or extended pumping durations of 100 s or 200 s as a more conservative alternative, can replace the aquifer characterization based on drawdown data. The new inversion strategy not only has less data uncertainty and equivalent inversion accuracy, but also can greatly enhance the repeatability of field tests and reduce the environmental impact of long-term pumping tests
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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