Quantitative interpretation of pore water O₂ and pH distributions in deep-sea sediments     

Parisa Jourabchi  Christof Meile  Philippe Van Cappellen 《Geochimica et cosmochimica acta》2008,72(5):1350-1364

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Using global node-based velocity in random walk particle tracking in variably saturated porous media: application to contaminant leaching from road constructions   总被引：2，自引：0，他引：2  

Chan-Hee Park  Christof Beyer  Sebastian Bauer  Olaf Kolditz 《Environmental Geology》2008,55(8):1755-1766

Precise and efficient numerical simulation of transport processes in subsurface systems is a prerequisite for many site investigation or remediation studies. Random walk particle tracking (RWPT) methods have been introduced in the past to overcome numerical difficulties when simulating propagation processes in porous media such as advection-dominated mass transport. Crucial for the precision of RWPT methods is the accuracy of the numerically calculated ground water velocity field. In this paper, a global node-based method for velocity calculation is used, which was originally proposed by Yeh (Water Resour Res 7:1216–1225, 1981). This method is improved in three ways: (1) extension to unstructured grids, (2) significant enhancement of computational efficiency, and (3) extension to saturated (groundwater) as well as unsaturated systems (soil water). The novel RWPT method is tested with numerical benchmark examples from the literature and used in two field scale applications of contaminant transport in saturated and unsaturated ground water. To evaluate advective transport of the model, the accuracy of the velocity field is demonstrated by comparing several published results of particle pathlines or streamlines. Given the chosen test problem, the global node-based velocity estimation is found to be as accurate as the CK method (Cordes and Kinzelbach in Water Resour Res 28(11):2903–2911, 1992) but less accurate than the mixed or mixed-hybrid finite element methods for flow in highly heterogeneous media. To evaluate advective–diffusive transport, a transport problem studied by Hassan and Mohamed (J Hydrol 275(3–4):242–260, 2003) is investigated here and evaluated using different numbers of particles. The results indicate that the number of particles required for the given problem is decreased using the proposed method by about two orders of magnitude without losing accuracy of the concentration contours as compared to the published numbers.  相似文献   

Modeling sulfur isotope fractionation and differential diffusion during sulfate reduction in sediments of the Cariaco Basin     

Michael A. Donahue  Christof Meile 《Geochimica et cosmochimica acta》2008,72(9):2287-2297

Sulfur isotope composition (δ³⁴S) profiles in sediment pore waters often show an offset between sulfate and sulfide much greater in magnitude than S isotope fractionations observed in pure cultures. A number of workers have invoked an additional reaction, microbial disproportionation of sulfur intermediates, to explain the offset between experimental and natural systems. Here, we present an alternative explanation based on modeling of pore water sulfate and sulfide concentrations and stable isotope data from the Cariaco Basin (ODP Leg 165, Site 1002B). The use of unique diffusion coefficients for and , based on their unequal molecular masses, resulted in an increase in the computed fractionation by almost 10‰, when compared to the common assumption of equal diffusion coefficients for the two species. These small differences in diffusion coefficients yield calculated isotopic offsets between coeval sediment pore water sulfate and sulfide without disproportionation (up to 53.4‰) that exceed the largest fractionations observed in experimental cultures. Furthermore, the diffusion of sulfide within sediment pore waters leads to values that are even greater than those predicted by our model for sulfate reduction with unique diffusion coefficients. These diffusive effects on the sulfur isotope composition of pore water sulfate and sulfide can impact our interpretations of geologic records of sulfate and sulfide minerals, and should be considered in future studies.  相似文献   

Response to comment by I.C. Bourg on “Modeling sulfur isotope fractionation and differential diffusion during sulfate reduction in sediments of the Cariaco Basin” by M.A. Donahue, J.P. Werne, C. Meile, and T.W. Lyons     

Michael A. Donahue  Christof Meile 《Geochimica et cosmochimica acta》2008,72(23):5855-5856

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Modelling the arctic convective boundary-layer with different turbulence parameterizations   总被引：1，自引：1，他引：0  

Christof Lüpkes  K. Heinke Schlünzen 《Boundary-Layer Meteorology》1996,79(1-2):107-130

Different parameterizations of subgrid-scale fluxes are utilized in a nonhydrostatic and anelastic mesoscale model to study their influence on simulated Arctic cold air outbreaks. A local closure, a profile closure and two nonlocal closure schemes are applied, including an improved scheme, which is based on other nonlocal closures. It accounts for continuous subgrid-scale fluxes at the top of the surface layer and a continuous Prandtl number with respect to stratification. In the limit of neutral stratification the improved scheme gives eddy diffusivities similar to other parameterizations, whereas for strong unstable stratifications they become much larger and thus turbulent transports are more efficient. It is shown by comparison of model results with observations that the application of simple nonlocal closure schemes results in a more realistic simulation of a convective boundary layer than that of a local or a profile closure scheme. Improvements are due to the nonlocal formulation of the eddy diffusivities and to the inclusion of heat transport, which is independent of local gradients (countergradient transport).  相似文献   

Temperature-dependent dissolution of residual non-aqueous phase liquids: model development and verification     

Steffi Popp  Christof Beyer  Andreas Dahmke  Nicolas Koproch  Ralf Köber  Sebastian Bauer 《Environmental Earth Sciences》2016,75(11):953

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Development of a semi-structured database for back-analysis of the foundation stiffness of offshore wind monopiles     

Stuyts  Bruno  Weijtjens  Wout  Devriendt  Christof 《Acta Geotechnica》2023,18(1):379-393

Acta Geotechnica - Offshore wind turbines founded on monopiles are highly dynamic structures in which the stiffness of the soil adjacent to the monopile controls the natural frequency of the...  相似文献   

Scale dependence of reaction rates in porous media     

Christof Meile  Kagan Tuncay 《Advances in water resources》2006

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Tsunami inundation in Napier, New Zealand, due to local earthquake sources     

Stuart A. Fraser  William L. Power  Xiaoming Wang  Laura M. Wallace  Christof Mueller  David M. Johnston 《Natural Hazards》2014,70(1):415-445

Deterministic analysis of local tsunami generated by subduction zone earthquakes demonstrates the potential for extensive inundation and building damage in Napier, New Zealand. We present the first high-resolution assessments of tsunami inundation in Napier based on full simulation from tsunami generation to inundation and demonstrate the potential variability of onshore impacts due to local earthquakes. In the most extreme scenario, rupture of the whole Hikurangi subduction margin, maximum onshore flow depth exceeds 8.0 m within 200 m of the shore and exceeds 5.0 m in the city centre, with high potential for major damage to buildings. Inundation due to single-segment or splay fault rupture is relatively limited despite the magnitudes of M_W 7.8 and greater. There is approximately 30 min available for evacuation of the inundation zone following a local rupture, and inundation could reach a maximum extent of 4 km. The central city is inundated by up to three waves, and Napier Port could be inundated repeatedly for 12 h. These new data on potential flow depth, arrival time and flow kinematics provide valuable information for tsunami education, exposure analysis and evacuation planning.  相似文献   

Impacts of the use of the geological subsurface for energy storage: an investigation concept     

Sebastian Bauer  Christof Beyer  Frank Dethlefsen  Peter Dietrich  Rainer Duttmann  Markus Ebert  Volker Feeser  Uwe Görke  Ralf Köber  Olaf Kolditz  Wolfgang Rabbel  Tom Schanz  Dirk Schäfer  Hilke Würdemann  Andreas Dahmke 《Environmental Earth Sciences》2013,70(8):3935-3943

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