台风"杜鹃"影响期间福建大风天气的特点及成因   总被引：3，自引：0，他引：3  

凌士兵  高珊  刘铭 《台湾海峡》2005,24(1):15-21

台风“杜鹃”影响期间，福建大风天气出现的比较早，而且范围比较大．本文通过对天气尺度的环境场、具有代表性的单站资料的对比分析，寻求大风出现的原因．还深入利用MM5模式对台风的气压场、风场、流场等进行数值模拟，分析结果表明台湾地形倒槽的形成对此次大风天气出现有着重要的作用，此外从流场分型的角度进一步分析台湾地形倒槽的形成原因．  相似文献   

The permeability of faults within siliciclastic petroleum reservoirs of the North Sea and Norwegian Continental Shelf   总被引：1，自引：0，他引：1  

Q. J. Fisher  R. J. Knipe 《Marine and Petroleum Geology》2001,18(10):1315

Faulting in Middle Jurassic reservoirs occurred at shallow depth during regional extension. Clean sandstones (<15% clay) deformed without significant grain fracturing and permeability reduction. Faults in impure sandstones (15–40% clay) experienced significant syn-deformation compaction and permeability reduction. Enhanced compaction during deeper burial reduced their permeabilities further from an average of 0.05 mD at <2.5 km to 0.001 mD at >4 km. Clay-rich sediments (>40% clay) deformed to produce clay smears with very low permeabilities (<0.001 mD). Faulting in the Rotliegendes occurred at greater depth during both basin extension and inversion. Extensional faulting produced cataclasites with permeability reductions of <10–>10⁶; their permeabilities range from 0.2 to 0.0001 mD and are inversely related to their maximum burial depth. Faults formed or reactivated during inversion experienced permeability increase. These results can be extrapolated to other hydrocarbon reservoirs if differences in stress and temperature history are taken into account.The permeability of most (>80%) faults is not sufficiently low, compared to their wallrock, to retard single-phase fluid flow on a km-scale. Nevertheless, most faults could retard the flow of a non-wetting phase if present at low saturations. It may be necessary to incorporate the two-phase fluid flow properties of fault rocks into reservoir simulators using upscaling or pseudoisation techniques. Fault property data should be calibrated against production data before it can be used confidently.  相似文献   

Estimation of Land Subsidence Based on Groundwater Flow Model   总被引：8，自引：0，他引：8  

Shui-Long Shen  Ye-Shuang Xu  Zhen-Shun Hong 《Marine Georesources & Geotechnology》2006,24(2):149-167

This article presents an approach for estimating land subsidence due to withdrawal of groundwater. The proposed method calculates the groundwater seepage in 3-D-condition and calculates the land subsidence one-dimensionally. The governing equation on groundwater seepage is based on the three-dimensional mass conservation law and the principle of effective stress. The land subsidence calculation method is derived based on the following assumptions: (1) displacements occur only in the vertical direction, and (2) in vertical direction the total stresses do not change. The governing equation is solved by numerical method, i.e., finite element method (FEM) in spatial discretization and finite difference method (FDM) in time series discretization. In FEM Galerkin method is adopted and in FDM, lumped matrix method is employed. The proposed method is calibrated via analyzing 1-D consolidation problem and the results are compared with those from Terzaghi's one-dimensional consolidation theory and oedometer test. The proposed method is employed to analyze the consolidation of a soft layer due to withdrawal of groundwater from an aquifer under it. Moreover, this method is also applied to a field case of land subsidence due to groundwater pumping in a gas production field in Japan. The analytical results are compared with the field observed data. The results show that this approach simulates the field case well.  相似文献   

Carbon cycling through the pelagic foodweb in the northern Humboldt Current off Chile (23{degrees}S)     

Gonzalez  H.E.; Giesecke  R.; Vargas  C.A.; Pavez  M.; Iriarte  J.; Santibanez  P.; Castro  L.; Escribano  R.; Pages  F. 《ICES Journal of Marine Science》2004,61(4):572-584

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Sediment movement under unidirectional flows: an assessment of empirical threshold curves   总被引：1，自引：0，他引：1  

D. Paphitis 《Coastal Engineering》2001,43(3-4)

A selection of threshold data sets from previous investigations is used to re-examine, selectively, some of the empirical curves that are most commonly used for the prediction of sediment threshold. Simple analytical formulae are derived describing single line curves for mean threshold values and envelopes for the initial movement of discrete particles and the commencement of mass sediment transport phases of the critical condition.The complexity of factors governing the prevailing conditions at threshold, together with the randomness of events, limits deterministic solutions; however, the curves provide an approach that can be used readily in practical applications. In contrast, the envelope presentation is more of a stochastic approach to the definition of threshold. It recognises that there is no definitive threshold condition under which a particular particle size can be displaced, but rather that a range of threshold values exist.The empirical threshold relationships were derived on the basis of a relatively large amount of data. However, the sources utilised have interpreted the ‘critical condition’ in various ways, implying that the formulae must be treated with caution in applications.  相似文献   

Does subterranean flow initiate mud banks off the southwest coast of India?     

K. K. Balachandran 《Estuarine, Coastal and Shelf Science》2004,59(4):589-598

Coastal waters off the southwest coast of India draw special attention because of the occurrence of mud banks at certain locations during southwest monsoon period. The present study puts forward a hypothesis of a subterranean flow, which could be a plausible mechanism to initiate the mud banks. The subterranean flow is believed to be coupled with activated trending faults and originate from the adjacent watershed (Vembanad Lake) separated from the sea by a narrow strip of land where submerged porous lime shell beds are present. When the lake water injection occurs through the fault, the mud/clay gets excited by its thixotrophic properties (as the overlying water looses its electrolyte) and transforms into a flowing fluid. The lowering of salinity due to the introduction of fresh water keeps the mud suspension in the water column for longer duration, leading to the formation of mud banks. The idea of subterranean flow through lime shell beds initiating formation of mud banks may apply globally to any coastal regions hugged by wetlands and of similar geological conditions.  相似文献   

A Numerical Model for Natural Backfill of Pipeline Trenches Subjected to Unidirectional／Oscillatory Flows     

LIANGDong-fang CHENGLiang KervinYEOW 《中国海洋工程》2005,19(2):269-286

A numerical model for the self-burial of a pipeline trench is developed. Morphological evolutions of a pipeline trench under steady-current or oscillatory-flow conditions are simulated with/without a pipeline inside the trench. The oscillatory flow in this study represents the action of waves. The two-dimensional Reynolds-averaged continuity and Navier-Stokes equations with the standard k-e turbulence closure, as well as the sediment transport equations, are solved with the finite difference method in a eurvilirrear coordinate system. Both bed and suspended loads of sediment transport are included in the morphological model. Because of the lack of experimental data on the backfilling of pipeline trenches, the numericalmodel is firstly verified against three closely-relevant experiments available in literature. A detailed measurement of the channel migration phenomenon under steady currents is employed for the assessment of the integral performance of themodel. The two experimental results from U-tube tests are used to validate the model‘s ability in predicting oscillatory flows. Different time-marching schemes are employed for the morphological computation under unidirectional and oscillatory conditions. It is found that vortex motions within the trench play an important role in the trench development.  相似文献   

Ecology of beach wrack in northern New England with special reference to Orchestia platensis     

Manaf I. Behbehani  Robert A. Croker   《Estuarine, Coastal and Shelf Science》1982,15(6)

The northern New England beach wrack community with special reference to the cosmopolitan amphipod crustacean, Orchestia platensis, was examined at estuarine and open coastal habitats. Beach wrack was dominated by the plant genera Ascophyllum, Zostera, Spartina and Chondrus, and was most abundant during spring and late summer. Animal community numbers, biomass and frequency in fresh to moderately decomposed wrack were dominated by O. platensis throughout the year at all habitats; oligochaetes and Collembola were also important. The abundance of O. platensis showed high spatial and temporal variability, with low abundance generally associated with decreased amounts of wrack during colder months. An exception was the winter presence of the species at one estuarine habitat, in patchy aggregations within gravel-cobble refuges. The abundance of O. platensis averaged 1280 (0.04 m²)⁻¹, with a maximum of 7040 (0.04 m²)⁻¹. The life cycle of O. platensis is bivoltine, with summer-hatched young reaching maturity within 1 month. Laboratory studies indicate females with up to 4 broods (30 days)⁻¹, averaging 18 eggs brood⁻¹.Orchestia platensis is omnivorous, eating fresh plant tissue, live oligochaetes, Limulus eggs and diatom ‘fuzz’. The rate of laboratory consumption of algae and Zostera was 0.05 mg plant mg⁻¹ wet body weight day⁻¹. Presumptive predators of O. platensis are juvenile green crab, Carcinus maenus, and the earwig. Anisolabis maritima. The mobility, aggregation and aggressiveness of O. platensis assist the species in establishing and maintaining populations in the rigorous wrack habitat. The general competitive superiority of O. platensis over its congener, O. gammarella, and the co-occurrence of these species on both eastern and western Atlantic shores is discussed.  相似文献   

含沙量对草地坡面径流泥沙沉积和水力特性的影响   总被引：2，自引：0，他引：2       下载免费PDF全文

潘成忠  马岚  上官周平 《水科学进展》2008,19(6):857-862

通过室内模拟试验,在坡度为3°和9°、流量为20和60L/min条件下研究了不同浓度(0～350kg/m3)含沙水流流经草地的泥沙沉积过程及其水力学特性。结果表明,坡面泥沙沉积量随含沙量的增加而增大,3°时泥沙沉积率与含沙量呈正相关,而9°时沉积率与含沙量呈反势。坡度对泥沙沉积影响显著,而在相同坡度条件下,两种流量试验的泥沙沉积量无明显差异。相同坡面坡上部位流速小于坡下部位,且含沙量对坡面流速影响较小。在相同坡度和流量条件下,水流雷诺数随含沙量的增大而减小。3°时水流阻力系数和曼宁糙率均随含沙量的增加而增大,而9°时含沙量对阻力影响不明显,因此在土壤侵蚀较严重地区进行坡面水文过程演算时需考虑含沙量对缓坡糙率的影响。  相似文献   

大港油田官142断块巨厚砂岩的储层流动单元   总被引：1，自引：1，他引：0  

窦松江  王庆魁  倪金钟  李桂林 《现代地质》2008,22(1):76-80,142

以黄骅坳陷官142断块中生界油藏为例,探讨巨厚砂岩储层流动单元的研究方法。巨厚砂岩储层流动单元研究包括两个层次,一为确定渗流屏障和连通体的分布,二为连通体内部储层渗流差异分析。研究表明,官142断块渗流屏障主要有泥质屏障、钙质砂岩胶结屏障和钙质砂砾岩胶结屏障3种类型。通过对连通体内部砂体渗流差异性分析,将连通体划分为3类流动单元。其中A类流动单元以粗孔、粗喉类型为主,渗流性能好,吸水强度大;B类流动单元储层为中孔、中喉型,渗流性能中等,吸水强度次之;C类流动单元储层多为粉细砂岩、砂砾岩或钙质胶结稍差的储层,吸水强度较差。通过流动单元的划分与研究,对预测该区的剩余油分布规律和优化调整方案提供依据。  相似文献