An enhanced constitutive model for crushable granular materials     

Ali Daouadji  Pierre‐Yves Hicher 《国际地质力学数值与分析法杂志》2010,34(6):555-580

Studies in the past have tried to reproduce the mechanical behaviour of granular materials by proposing constitutive relations based on a common assumption that model parameters and parameters describing the properties, including gradation of individual grains are inevitably linked. However successful these models have proved to be, they cannot account for the changes in granular assembly behaviour if the grains start to break during mechanical loading. This paper proposes to analyse the relation between grading change and the mechanical behaviour of granular assembly. A way to model the influence of grain breakage is to use a critical state‐based model. The influence of the amount of grain breakage during loading, depending on the individual grain strength and size distribution, can be introduced into constitutive relations by means of a new parameter that controls the evolution of critical state with changes in grain size distribution. Experimental data from a calcareous sand, a quartz sand, and a rockfill material were compared with numerical results and good‐quality simulations were obtained. The main consequences of grain breakage are increased compressibility and a gradual dilatancy disappearance in the granular material. The critical state concept is also enriched by considering its overall relation to the evolution of the granular material. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Lateral friction in the oceans as an effect of potential vorticity mixing     

Pierre Welander 《地球物理与天体物理流体动力学》2013,107(1):173-189

Abstract

Applying a mixing-length calculation to potential vorticity rather than to momentum a new type of lateral friction appears in the oceanic mass transport equations. This friction is evaluated for the special case of horizontally homogeneous, quasi-geostrophic turbulence. The main effect is a westward force arising from the so-called β-term. This produces an additional southward interior transport and a strengthening of the western boundary current. A turbulent exchange coefficient K^H = 10⁸ em²s^?1 is sufficient to give a Gulf Stream transport twice that obtained by the classical Sverdrup model.  相似文献   

XMM-LSS discovery of a  z= 1.22  galaxy cluster     

M. N. Bremer  I. Valtchanov  J. Willis  B. Altieri  S. Andreon  P. A. Duc  F. Fang  C. Jean  C. Lonsdale  F. Pacaud  M. Pierre  D. L. Shupe  J. A. Surace  I. Waddington 《Monthly notices of the Royal Astronomical Society》2006,371(3):1427-1434

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Modeling fish growth and reproduction in the context of the Dynamic Energy Budget theory to predict environmental impact on anchovy spawning duration     

Laure Pecquerie  Pierre Petitgas  Sebastiaan A.L.M. Kooijman 《Journal of Sea Research》2009,62(2-3):93

Spawning location and timing are critical for understanding fish larval survival. The impact of a changing environment on spawning patterns is, however, poorly understood. A novel approach is to consider the impact of the environment on individual life histories and subsequent spawnings. In the present work, we extend the Dynamic Energy Budget (DEB) theory to investigate how environment variability impacts the spawning timing and duration of a multiple-batch spawning species. The model is successfully applied to reproduce the growth and reproduction of anchovy (Engraulis encrasicolus) in the Bay of Biscay. The model captures realistically the start and ending of the spawning season, including the timing of the spawning events, and the change in egg number per batch. Using a realistic seasonal forcing of temperature and food availability derived from a bio-physical model, our simulation results show that two thirds of the total spawned mass already accumulates before the start of the spawning season and that the condition factor increases with body length. These simulation results are in accordance with previous estimations and observations on growth and reproduction of anchovy. Furthermore, we show how individuals of equal length can differ in reproductive performance according to the environmental conditions they encounter prior to the spawning season. Hatch date turns out to be key for fecundity at age-1 as it partly controls the ability to build up reserves allocated to reproduction. We suggest the model can be used to realistically predict spawning in spatially and temporally varying environments and provide initial conditions for bio-physical models used to predict larval survival.  相似文献   

Drained triaxial testing of shales: insight from the Opalinus Clay     

Delage  Pierre  Belmokhtar  Malik 《Acta Geotechnica》2022,17(7):2855-2874

Acta Geotechnica - The investigation of the mechanical behaviour of swelling claystones and shales is challenging because of their very low permeability and of their high sensitivity to changes in...  相似文献   

Efficiency of a two-step upscaling method for permeability evaluation at Darcy and pore scales     

Pierre Horgue  Romain Guibert  Hervé Gross  Patrice Creux  Gérald Debenest 《Computational Geosciences》2015,19(6):1159-1169

This work presents a new subdivision method to upscale absolute permeability fields. This process, called two-step method, consists in (i) solving micro-scale equations on subdomains obtained from the full domain regular decomposition and (ii) solve a second upscaling with Darcy’s law on the permeability fields obtained in the first step. The micro-scale equations used depend on the case studied. The two-step upscaling process is validated on randomly generated Darcy-scale permeability fields by measuring the numerical error induced by upscaling. The method is then applied to real domains obtained from sandstone micro-tomographic images. The method specificities due to pore-space structure are discussed. The main advantage of the two-step upscaling method resides in the drastic reduction of computational costs (CPU time and memory usage) while maintaining a numerical error similar to that of other upscaling procedures. This new upscaling method may improve permeability predictions by the use of finer meshes or larger sample volumes.  相似文献   

Evolution of a Late Oxfordian: early Kimmeridgian carbonate platform,French Jura Mountains     

Nicolas Olivier  Elsa Cariou  Pierre Hantzpergue 《Swiss Journal of Geoscience》2015,108(2-3):273-288

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Deciphering neotectonics from river profile analysis in the karst Jura Mountains (northern Alpine foreland)     

Mickael Rabin  Christian Sue  Pierre G. Valla  Jean-Daniel Champagnac  Nicolas Carry  Vincent Bichet  Urs Eichenberger  Jacques Mudry 《Swiss Journal of Geoscience》2015,108(2-3):401-424

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Influence d'un changement climatique dû à une hausse de gaz à effet de serre sur l'agriculture au quebec     

Bhawan Singh  Mustapha El Maayar  Pierre André  Jean‐Pierre Thouez  Christopher Bryant  Denis Provençal 《大气与海洋》2013,51(2):379-399

Abstract

This study, using a climate change scenario generated by the Canadian Climate Centre (CCC) general circulation model (GCM) examines the impacts of such a climate change on agriculture in southern Quebec. Using a crop model from the Food and Agriculture Organization (FAO), yield responses of a variety of cereals, legumes, oleaginous and special crops to climate change are analysed and discussed.

Results show that under the 2 × CO₂ climate scenario the growing season would be longer and accumulation of corn heat units and growing degree days would be more important than under actual climate (1961–1990). One of the more important results of this study is that, on the one hand yield of C₃ cereals would be lower and that of C₄ cereals higher in most agricultural regions. On the other hand, the direct fertilisation effect of increased CO₂ is not considered. It must be cautioned however that we can not generalise results obtained for one legume crop to all legumes.  相似文献   

Climate and climate change in western canada as simulated by the Canadian regional climate model     

Rene Laprise  Daniel Caya  Michel Giguere  Guy Bergeron  Hélène Côté  Jean‐Pierre Blanchet 《大气与海洋》2013,51(2):119-167

Abstract

A þrst climate simulation performed with the novel Canadian Regional Climate Model (CRCM) is presented. The CRCM is based on fully elastic non‐hydrostatic þeld equations, which are solved with an efþcient semi‐implicit semi‐Lagrangian (SISL) marching algorithm, and on the parametrization package of subgrid‐scale physical effects of the second‐generation Canadian Global Climate Model (GCMII). Two 5‐year integrations of the CRCM nested with GCMII simulated data as lateral boundary conditions are made for conditions corresponding to current and doubled CO₂ scenarios. For these simulations the CRCM used a grid size of 45 km on a polar‐stereographic projection, 20 scaled‐height levels and a time step of 15 min; the nesting GCMII has a spectral truncation of T32, 10 hybrid‐pressure levels and a time step of 20 min. These simulations serve to document: (1) the suitability of the SISL numerical scheme for regional climate modelling, (2) the use of GCMII physics at much higher resolution than in the nesting model, (3) the ability of the CRCM to add realistic regional‐scale climate information to global model simulations, and (4) the climate of the CRCM compared to that of GCMII under two greenhouse gases (GHG) scenarios.  相似文献