Numerical simulation of overflow at vertical weirs using a hybrid level set/VOF method     

Xin LvQingping Zou  Dominic Reeve 《Advances in water resources》2011,34(10):1320-1334

This paper presents the applications of a newly developed free surface flow model to the practical, while challenging overflow problems for weirs. Since the model takes advantage of the strengths of both the level set and volume of fluid methods and solves the Navier-Stokes equations on an unstructured mesh, it is capable of resolving the time evolution of very complex vortical motions, air entrainment and pressure variations due to violent deformations following overflow of the weir crest. In the present study, two different types of vertical weir, namely broad-crested and sharp-crested, are considered for validation purposes. The calculated overflow parameters such as pressure head distributions, velocity distributions, and water surface profiles are compared against experimental data as well as numerical results available in literature. A very good quantitative agreement has been obtained. The numerical model, thus, offers a good alternative to traditional experimental methods in the study of weir problems.  相似文献   

Developing carbon budgets for UK agriculture, land-use, land-use change and forestry out to 2022   总被引：1，自引：0，他引：1  

Dominic Moran  Michael MacLeod  Eileen Wall  Vera Eory  Alistair McVittie  Andrew Barnes  R. M. Rees  Cairistiona F. E. Topp  Guillaume Pajot  Robin Matthews  Pete Smith  Andrew Moxey 《Climatic change》2011,105(3-4):529-553

This paper derives a notional future carbon budget for UK agriculture, land use, land use change and forestry sectors (ALULUCF). The budget is based on a bottom-up marginal abatement cost curve (MACC) derived for a range of mitigation measures for specified adoption scenarios for the years 2012, 2017 and 2022. The results indicate that in 2022 around 6.36 MtCO₂e could be abated at negative or zero cost. Furthermore, in the same year, over 17% of agricultural GHG emissions (7.85 MtCO₂e) could be abated at a cost of less than the 2022 Shadow Price of Carbon (£34 (tCO₂e)^???1). The development of robust MACCs faces a range of methodological hurdles that complicate cost-effectiveness appraisal in ALULUCF relative to other sectors. Nevertheless, the current analysis provides an initial route map of efficient measures for mitigation in UK agriculture.  相似文献   

Reply to discussion of “Measurements of sheet flow transport in acceleration-skewed oscillatory flow and comparison with practical formulations” by D.A. van der A,T. O'Donoghue and J.S. Ribberink     

Dominic A. van der A  Tom O'Donoghue  Jan S. Ribberink 《Coastal Engineering》2011

This is a reply to the discussion by Camenen and Larson (Coastal Eng., 58, 2011, 131–134) of “Measurements of sheet flow transport in acceleration-skewed oscillatory flow and comparison with practical formulations” by D.A. van der A et al. (Coastal Eng. 57, 2010, 331–342). The authors of the original paper (Van der A et al., 2010) thank the discussers for their interest in and comments on the work presented in the paper.  相似文献   

Mission Concept for the Single Aperture Far-Infrared (SAFIR) Observatory     

Dominic J. Benford  Michael J. Amato  John C. Mather  S. Harvey Moseley Jr  David T. Leisawitz 《Astrophysics and Space Science》2004,294(3-4):177-212

The Single Aperture Far-InfraRed (SAFIR) Observatory’s science goals are driven by the fact that the earliest stages of almost all phenomena in the universe are shrouded in absorption by and emission from cool dust and gas that emits strongly in the far-infrared (40μ–200μ) and submillimeter (200μ–1 mm). In the very early universe, the warm gas of newly collapsing, unenriched galaxies will be revealed by molecular hydrogen emission lines at these long wavelengths. High redshift quasars are found to have substantial reservoirs of cool gas and dust, indicative of substantial metal enrichment early in the history of the universe. As a result, even early stages of galaxy formation will show powerful far-infrared emission. The combination of strong dust emission and large redshift (1 < z < 7) of these galaxies means that they can only be studied in the far-infrared and submillimeter. For nearby galaxies, many of the most active galaxies in the universe appear to be those whose gaseous disks are interacting in violent collisions. The details of these galaxies, including the effect of the central black holes that probably exist in most of them, are obscured to shorter wavelength optical and ultraviolet observatories by the large amounts of dust in their interstellar media. Within our own galaxy, the earliest stages of star formation, when gas and dust clouds are collapsing and the beginnings of a central star are taking shape, can only be observed in the far-infrared and submillimeter. The cold dust that ultimately forms the planetary systems, as well as the cool “debris” dust clouds that indicate the likelihood of planetary sized bodies around more developed stars, can only be observed at wavelengths longward of 20μ. Over the past several years, there has been an increasing recognition of the critical importance of the far-infrared to submillimeter spectral region to addressing fundamental astrophysical problems, ranging from cosmological questions to understanding how our own Solar System came into being. The development of large, far-infrared telescopes in space has become more feasible with the combination of developments for the James Webb Space Telescope (JWST) of enabling breakthroughs in detector technology. We have developed a preliminary but comprehensive mission concept for SAFIR, as a 10 m-class far-infrared and submillimeter observatory that would begin development later in this decade to meet the needs outlined above. Its operating temperature (≤4 K) and instrument complement would be optimized to reach the natural sky confusion limit in the far-infrared with diffraction-limited performance down to at least the atmospheric cutoff, λ {>rsim} 40 {μ}. This would provide a point source sensitivity improvement of several orders of magnitude over that of the Spitzer Space Telescope (previously SIRTF) or the Herschel Space Observatory. Additionally, it would have an angular resolution 12 times finer than that of Spitzer and three times finer than Herschel. This sensitivity and angular resolution are necessary to perform imaging and spectroscopic studies of individual galaxies in the early universe. We have considered many aspects of the SAFIR mission, including the telescope technology (optical design, materials, and packaging), detector needs and technologies, cooling method and required technology developments, attitude and pointing, power systems, launch vehicle, and mission operations. The most challenging requirements for this mission are operating temperature and aperture size of the telescope, and the development of detector arrays. SAFIR can take advantage of much of the technology under development for JWST, but with much less stringent requirements on optical accuracy.  相似文献   

Exploring biological constraints on the glacial history of Antarctica     

Peter Convey  Mark I. Stevens  Dominic A. Hodgson  John L. Smellie  Claus-Dieter Hillenbrand  David K.A. Barnes  Andrew Clarke  Philip J.A. Pugh  Katrin Linse  S. Craig Cary 《Quaternary Science Reviews》2009,28(27-28):3035-3048

The evolutionary and biogeographic history of the contemporary Antarctic terrestrial and marine biotas reveals many components of ancient origin. For large elements of the terrestrial biota, long-term isolation over timescales from hundreds of thousands to tens of millions of years, and thus persistence through multiple glacial cycles, now appears to be the norm rather than the exception. For the marine biota there are some parallels with benthic communities also including ancient components, together with an incidence of species-level endemism indicating long-term isolation on the Antarctic continental shelf. Although it has long been known that a few ice-free terrestrial locations have existed in Antarctica for up to 10–12 million years, particularly in the Dry Valleys of Victoria Land along with certain nunataks and higher regions of large mountain ranges, these do not provide potential refugia for the majority of terrestrial biota, which occur mainly in coastal and/or low-lying locations and exhibit considerable biogeographic regionalisation within the continent. Current glacial models and reconstructions do not have the spatial resolution to detect unequivocally either the number or geographical distribution of these glacial refugia, or areas of the continental shelf that have remained periodically free from ice scouring, but do provide limits for their maximum spatial extent. Recent work on the evolution of the terrestrial biota indicates that refugia were much more widespread than has been recognised and it is now clear that terrestrial biology provides novel constraints for reconstructing the past glacial history of Antarctica, and new marine biological investigations of the Antarctic shelf are starting to do likewise.  相似文献   

Magnetometry for Archaeologists. Arnold Aspinall,Chris Gaffney,and Armin Schmidt. 2008. Altamira Press,Lanham, Maryland,x + 208 pp., ISBN: 978‐0‐7591‐1106‐6, $75.00 (hardcover).     

Dominic Lacroix 《Geoarchaeology》2012,27(2):180-182

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Porosity and permeability in sediment mixtures   总被引：1，自引：1，他引：0  

Kamann PJ  Ritzi RW  Dominic DF  Conrad CM 《Ground water》2007,45(4):429-438

Porosity in sediments that contain a mix of coarser- and finer-grained components varies as a function of the porosity and volume fraction of each component. We considered sediment mixtures representing poorly sorted sands and gravely sands. We expanded an existing fractional-packing model for porosity to represent mixtures in which finer grains approach the size of the pores that would exist among the coarser grains alone. The model well represents the porosity measured in laboratory experiments in which grain sizes and volume fractions were systematically changed within sediment mixtures. Permeability values were determined for these sediment mixtures using a model based on grain-size statistics and the expanded fractional-packing porosity model. The permeability model well represents permeability measured in laboratory experiments using air- and water-based permeametry on the model sediment mixtures.  相似文献   

A geological constraint on relative sea level in Marine Isotope Stage 3 in the Larsemann Hills, Lambert Glacier region, East Antarctica (31 366–33 228 cal yr BP)     

Dominic A. Hodgson  Elie Verleyen  Wim Vyverman  Koen Sabbe  Melanie J. Leng  Matthew D. Pickering  Brendan J. Keely 《Quaternary Science Reviews》2009,28(25-26):2689-2696

In this paper we present geological evidence from the Larsemann Hills (Lambert Glacier – Amery Ice Shelf region, East Antarctica) of marine sediments at an altitude of c. 8 m a.s.l., as revealed by diatom, pigment and geochemical proxies in a lake sediment core. The sediments yielded radiocarbon dates between c. 26 650 and 28 750 ¹⁴C yr BP (31 366–33 228 cal yr BP). This information can be used to constrain relative sea level adjacent to the Lambert Glacier at the end of Marine Isotope Stage 3. These data are compared with the age and altitude of Marine Isotope Stage 3 marine deposits elsewhere in East Antarctica and discussed with reference to late Quaternary ice sheet history and eustatic sea-level change.  相似文献   

Structure of the footwall of a listric fault system revealed by 3D seismic data from the Niger Delta     

Dominic Maloney  Richard Davies  Jonathan Imber  Stephen King 《Basin Research》2012,24(1):107-123

We use three‐dimensional (3D) seismic reflection data to analyse the architecture of the footwall of a listric fault, in a gravitationally driven extensional system, in the north‐western Niger Delta. In contrast to conventional listric normal fault models with a single master listric fault plane the level of detachment switches from a deeper to shallower level. The footwall evolves through the generation of new master detachment faults and detachments, which transfers hanging wall rocks into the footwall. New detachments form by branching off pre‐existing detachment levels, cutting‐up through stratigraphy to the next mechanical weakness, separating discrete sections of extended strata. As a consequence a deeper, older array of seaward‐dipping, tilted extensional fault blocks is now located in the footwall beneath the master listric detachment fault. The structural complexity located below the master detachment fault highlights extensional episodes on separate detachment faults that are not captured in conventional listric models. We speculate that changes in the level of the detachment are caused by mechanical weaknesses controlled by lithology, pore pressure and episodes of sediment loading related to deltaic progradation.  相似文献   

Modeling multiscale heterogeneity and aquifer interconnectivity   总被引：2，自引：0，他引：2  

Proce CJ  Ritzi RW  Dominic DF  Dai Z 《Ground water》2004,42(5):658-670

A number of methods involving indicator geostatistics were combined in a methodology for characterizing and modeling multiscale heterogeneity. The methodology circumvents sources of bias common in data from borehole logs. We applied this methodology to the complex heterogeneity within a regional system of buried valley aquifers, which occurs in the western glaciated plains of North America and includes the Spiritwood Aquifer. The region is conceptualized as having a hierarchical organization with three facies assemblage types (large-scale heterogeneity) and two facies types within each assemblage (small-scale heterogeneity). We statistically characterized the sedimentary architecture at both scales, formulated indicator correlation models from those characterizations, and used the models to simulate the architecture in a multiscale realization. We focused on the interconnectivity of units creating higher-permeability pathways. Higher-permeability pathways span the realization even though the proportion of higher-permeability facies is less than the percolation threshold. Thus, geologic structures as represented in the indicator correlation models create interconnectivity above that which would occur if the higher-permeability facies were randomly placed. This amount of interconnection among higher-permeability facies within the multiscale realization is consistent with that suggested in prior hydraulic and geochemical studies of the regional system.  相似文献