Dispersion in the Wake of a Rectangular Building: Validation of Two Reynolds-Averaged Navier–Stokes Modelling Approaches     

Catherine Gorlé  Jeroen van Beeck  Patrick Rambaud 《Boundary-Layer Meteorology》2010,137(1):115-133

When modelling the turbulent dispersion of a passive tracer using Reynolds-averaged Navier–Stokes (RANS) simulations, two different approaches can be used. The first consists of solving a transport equation for a scalar, where the governing parameters are the mean velocity field and the turbulent diffusion coefficient, given by the ratio of the turbulent viscosity and the turbulent Schmidt number Sc _t . The second approach uses a Lagrangian particle tracking algorithm, where the governing parameters are the mean velocity and the fluctuating velocity field, which is determined from the turbulence kinetic energy and the Lagrangian time T _L . A comparison between the two approaches and wind-tunnel data for the dispersion in the wake of a rectangular building immersed in a neutral atmospheric boundary layer (ABL) is presented. Particular attention was paid to the influence of turbulence model parameters on the flow and concentration field. In addition, an approach to estimate Sc _t and T _L based on the calculated flow field is proposed. The results show that applying modified turbulence model constants to enable correct modelling of the ABL improves the prediction for the velocity and concentration fields when the modification is restricted to the region for which it was derived. The difference between simulated and measured concentrations is smaller than 25% or the uncertainty of the data on 76% of the points when solving the transport equation for a scalar with the proposed formulation for Sc _t , and on 69% of the points when using the Lagrangian particle tracking with the proposed formulation for T _L .  相似文献   

Towards Usability Engineering for Online Editors of Volunteered Geographic Information: A Perspective on Learnability     

Catherine E. Jones  Patrick Weber 《Transactions in GIS》2012,16(4):523-544

This article presents one of the first systematic usability investigations for a Volunteered Geographic Information (VGI) editor. This research is motivated by the fact that although VGI is now widely consumed, contribution rates are lagging considerably. Compared to traditional GIS interfaces, with complex interfaces resulting in high cognitive loads and barriers to participation, VGI tools and interfaces need to be easy to use and learn to encourage and facilitate contributions. This article develops a case study of OpenStreetMap, one of the most successful VGI projects, and its default editor, Potlatch2. Ten participants with no prior experience of VGI contribution, were instructed to contribute data to OSM in a structured exercise, while being monitored using an eye tracker and audio/video screen capture software. Each participant was asked to Think Aloud, i.e. describe what they were thinking and doing as they completed the tasks. The results highlight significant usability issues impacting learnability, especially from the perspective of a new contributor: hidden functionality, lack of user feedback between interactions and the inefficient and inconsistent placement of functionality and map controls. The facilitation of VGI contributions clearly depends on designing targeted interfaces, optimized to the needs of specific levels of contributors with defined goals and expectations.  相似文献   

Solar EUV emission line profiles of Si ii and Si iii and their center to limb variations     

K. R. Nicolas  G. E. Brueckner  R. Tousey  D. A. Tripp  O. R. White  R. G. Athay 《Solar physics》1977,55(2):305-319

Spectral line profiles of Si ii and Si iii are presented which were observed both at solar center and near the quiet solar limb with the Naval Research Laboratory EUV spectrograph of ATM/SKYLAB. Absolute intensities and line profiles are derived from the photographic data. A brief discussion is given of their center-to-limb variations and of the optical thickness of the chromosphere in these lines. Nonthermal broadening velocities are found for the optically thin lines from their full width at half maximum intensity (FWHM).Also at High Altitude Observatory for part of this work.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

P-Wave Velocities in the Upper Mantle Beneath the Australian Shield from Earthquake Data     

R. E. White 《Geophysical Journal International》1971,24(2):109-118

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A practical model for mobile, residual, and entrapped NAPL in water-wet porous media     

White MD  Oostrom M  Lenhard RJ 《Ground water》2004,42(5):734-746

Flow of nonvolatile nonaqueous phase liquid (NAPL) and aqueous phases that account for mobile, entrapped, and residual NAPL in variably saturated water-wet porous media is modeled and compared against results from detailed laboratory experiments. Residual saturation formation in the vadose zone is a process that is often ignored in multifluid flow simulators, which might cause an overestimation of the volume of NAPL that reaches the ground water. Mobile NAPL is defined as being continuous in the pore space and flows under a pressure gradient or gravitational body force. Entrapped NAPL is defined as being occluded by the aqueous phase, occurring as immobile ganglia surrounded by aqueous phase in the pore space and formed when NAPL is replaced by the aqueous phase. Residual NAPL is defined as immobile, nonwater entrapped NAPL that does not drain from the pore spaces and is conceptualized as being either continuous or discontinuous. Free NAPL comprises mobile and residual NAPL. The numerical model is formulated on mass conservation equations for oil and water, transported via NAPL and aqueous phases through variably saturated porous media. To account for phase transitions, a primary variable switching scheme is implemented for the oil-mass conservation equation over three phase conditions: (1) aqueous or aqueous-gas with dissolved oil, (2) aqueous or aqueous-gas with entrapped NAPL, and (3) aqueous or aqueous gas with free NAPL. Two laboratory-scale column experiments are modeled to verify the numerical model. Comparisons between the numerical simulations and experiments demonstrate the necessity to include the residual NAPL formation process in multifluid flow simulators.  相似文献   

Phyllosilicate minerals in the hydrothermal mafic–ultramafic-hosted massive-sulfide deposit of Ivanovka (southern Urals): comparison with modern ocean seafloor analogues     

Paolo?NimisEmail author  Svetlana?G.?Tesalina  Paolo?Omenetto  Paola?Tartarotti  Catherine?Lerouge 《Contributions to Mineralogy and Petrology》2004,147(3):363-383

We have studied textural relationships and compositions of phyllosilicate minerals in the mafic–ultramafic-hosted massive-sulfide deposit of Ivanovka (Main Uralian Fault Zone, southern Urals). The main hydrothermal phyllosilicate minerals are Mg-rich chlorite, variably ferroan talc, (Mg, Si)-rich and (Ca, Na, K)-poor saponite (stevensite), and serpentine. These minerals occur both as alteration products after mafic volcanics and ultramafic protoliths and, except serpentine, as hydrothermal vein and seafloor mound-like precipitates associated with variable amounts of (Ca, Mg, Fe)-carbonates, quartz and Fe and Cu (Co, Ni) sulfides. Brecciated mafic lithologies underwent pervasive chloritization, while interlayered gabbro sills underwent partial alteration to chlorite + illite ± actinolite ± saponite ± talc-bearing assemblages and later localized deeper alteration to chlorite ± saponite. Ultramafic and mixed ultramafic–mafic breccias were altered to talc-rich rocks with variable amounts of chlorite, carbonate and quartz. Chloritization, locally accompanied by formation of disseminated sulfides, required a high contribution of Mg-rich seawater to the hydrothermal fluid, which could be achieved in a highly permeable, breccia-dominated seafloor. More evolved hydrothermal fluids produced addition of silica, carbonates and further sulfides, and led to local development of saponite after chlorite and widespread replacement of serpentine by talc. The Ivanovka deposit shows many similarities with active and fossil hydrothermal sites on some modern oceanic spreading centers characterized by highly permeable upflow zones. However, given the arc signature of the ore host rocks, the most probable setting for the observed alteration–mineralization patterns is in an early-arc or forearc seafloor–subseafloor environment, characterized by the presence of abundant mafic–ultramafic breccias of tectonic and/or sedimentary origin.Editorial responsibility: J. Hoefs  相似文献   

Pitfalls in geothermobarometry of eclogites: Fe<Superscript>3+</Superscript> and changes in the mineral chemistry of omphacite at ultrahigh pressures   总被引：1，自引：0，他引：1  

Alexander?ProyerEmail author  Edgar?Dachs  Catherine?McCammon 《Contributions to Mineralogy and Petrology》2004,147(3):305-318

The relatively low-variance mineral assemblage of a talc-kyanite eclogite from Dabie Shan enabled application of both conventional geothermobarometers (garnet-clinopyroxene geothermometer and the garnet-omphacite-phengite geobarometer) and a multi-equilibrium method to determine peak P-T conditions (THERMOCALC, average PT). The results were highly discrepant: 840 °C / 31.1 kbar vs. 590 °C / 29.8 kbar. Mössbauer spectroscopy showed that Fe³⁺/Fe_total in omphacite was significantly higher than the value obtained from standard formula recalculation. When the activities were corrected for Fe endmembers, geothermobarometry gave consistent results (606 °C / 31.3 kbar vs. 585 °C / 30.8 kbar). These are close to those obtained earlier by average PT, confirming the robustness of the multi-equilibrium approach. The high Fe³⁺ concentration in omphacite is best explained using a Ca-eskola endmember Ca_0.5[]_0.5AlSi₂O₆ and allowing corresponding vacancies in the omphacite structure.Editorial responsibility: W. Schreyer  相似文献   

Stibnite microstructures as imprints of fault movement     

Jean-Philippe Bellot  Laurent Bailly  Catherine Lerouge  Vincent Bouchot 《Mineralium Deposita》2004,39(5-6):576-582

The natural deformation of stibnite in relation to the kinematic history of a regional fault is resolved using microstructural analysis of massive stibnite along the Biards Fault in the Massif Central (France). Stibnite underwent intra-crystalline deformation associated with a strong linear and planar anisotropy. Lepidoblastic textures, undulatory extinction of oriented grains, growth of antimony between these grains, and a colour change of stibnite from white to black, result from dynamic recrystallisation. A range of asymmetric microstructures indicate non-coaxial deformation and a left-lateral sense of shear, related to the movement of the fault zone. The computed displacement corresponds to the geological offsets measured along the fault. We conclude that stibnite has microstructurally recorded the bulk kinematics of its host fault zone.Editorial Handling: F. Tornos  相似文献   

Datation U–Pb des deux faciès du granite de Soultz (Fossé rhénan,France)     

Alain Cocherie  Catherine Guerrot  C.Mark Fanning  Albert Genter 《Comptes Rendus Geoscience》2004,336(9):775-787

Deep boreholes drilled in the basement of the Rhine Graben at Soultz-sous-Forêts have shown the presence of an ubiquitous monzogranite. Borehole GPK-2, with a total depth of 5090 m, also intersected a more leucocratic fine-grained two-mica granite, locally present below 4860 m depth and continuously found between 5047 and 5090 m. Thanks to trace elements and in particular to REE (rare-earth elements), it could be shown that the leucocratic rock is a differentiated expression of the potassic magma that was at the origin of the monzogranite pluton. This model agrees with Sr–Nd isotope data, even though a slight contribution from the pre-existing basement should be considered as well. Use of the U–Pb method on monzogranite from EPS-1 – after zircon dissolution – has yielded an emplacement age of 334.0+3.8/?3.5 Ma $\text{(2}\text{σ)}$. Point dates obtained by SHRIMP II on the rare zircons from the fine-grained granite showed that it was emplaced in a basement with very heterogeneous ages, ranging from Early Proterozoic to Silurian. The estimated crystallization age of the last granite is 327±7 Ma $\text{(2}\text{σ)}$, slightly later than, or sub-contemporaneous with, the emplacement of the common monzogranite, in agreement with structural constrains. To cite this article: A. Cocherie et al., C. R. Geoscience 336 (2004).  相似文献   

Role of the photo-Fenton reaction in the production of hydroxyl radicals and photobleaching of colored dissolved organic matter in a coastal river of the southeastern United States   总被引：4，自引：0，他引：4  

Emily?M.?White  Pamela?P.?Vaughan  Richard?G.?ZeppEmail author 《Aquatic Sciences - Research Across Boundaries》2003,65(4):402-414

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