Steady‐state analytical solutions of flow and deformation coupling due to a point sink within a finite fluid‐saturated poroelastic layer          下载免费PDF全文

P. Li  K. Wang  G. Fang  D. Lu 《国际地质力学数值与分析法杂志》2017,41(8):1093-1107

An exact steady‐state closed‐form solution is presented for coupled flow and deformation of an axisymmetric isotropic homogeneous fluid‐saturated poroelastic layer with a finite radius due to a point sink. The hydromechanical behavior of the poroelastic layer is governed by Biot's consolidation theory. Boundary conditions on the lateral surface are specifically chosen to match the appropriate finite Hankel transforms and simplify the transforms of the governing equations. Ordinary differential equations in the transformed domain are solved, and then the analytical solutions in the physical space for the pore pressure and the displacements are finally obtained by using finite Hankel inversions. The analytical solutions at some special locations such as the top and bottom surfaces, lateral surface, and the symmetrical axis are given and analyzed. And a case study for the consolidation of a water‐saturated soft clay layer due to pumping is conducted. The analytical solution is verified against the finite element solution. Meanwhile, an analysis of coupled hydromechanical behavior is carried out herein. The presented analytical solution is an exact solution to the practical poroelastic problem within an axisymmetric finite layer. It can provide us a better understanding of the poroelastic behavior of the finite layer due to fluid extraction. Besides, it can be applied to calibrate numerical schemes of axisymmetric poroelasticity within finite domains. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Influence of heterogeneity on unsaturated hydraulic properties: (1) local heterogeneity and scale effect     

Pen‐Yuan Chen  Chu‐Hui Chen  Nien‐Sheng Hsu  Cheng‐Mau Wu  Jet‐Chau Wen 《水文研究》2012,26(23):3593-3603

Spatial heterogeneity is ubiquitous in nature, which may significantly affect the soil hydraulic property curves. The models of a closed‐form functional relationship of soil hydraulic property curves (e.g. VG model or exponential model) are valid at point or local scale based on a point‐scale hydrological process, but how do scale effects of heterogeneity have an influence on the parameters of these models when the models are used in a larger scale process? This paper uses a two‐dimensional variably saturated flow and solute transport finite element model (VSAFT2) to simulate variations of pressure and moisture content in the soil flume under a constant head boundary condition. By changing different numerical simulation block sizes, a quantitative evaluation of parameter variations in the VG model, resulting from the scale effects, is presented. Results show that the parameters of soil hydraulic properties are independent of scale in homogeneous media. Parameters of α and n in homogeneous media, which are estimated by using the unsaturated hydraulic conductivity curve (UHC) or the soil water retention curve (WRC), are identical. Variations of local heterogeneities strongly affect the soil hydraulic properties, and the scale affects the results of the parameter estimations when numerical experiments are conducted. Furthermore, the discrepancy of each curve becomes considerable when moisture content becomes closer to a dry situation. Parameters estimated by UHC are totally different from the ones estimated by WRC. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Jet instability and the stabilizing effect of topography on jets in two-layer rotating systems     

Don L. Boyer  Rui-Rong Chen 《地球物理与天体物理流体动力学》2013,107(1-3):45-70

Abstract

Laboratory experiments concerning azimuthal jets in two-layer rotating systems in the absence and presence of bottom topography aligned along the jets have been conducted. The jets were forced by the selective withdrawal of fluid from the upper layer of a two-fluid system contained in a circular dishpan geometry. The principal parameters measured in the experiments were the jet Rossby number, Ro, and a stratification parameter F = r ₁/(λ₁λ₂)^1/2 where r ₁ is the radius of the circular disc used for the selective withdrawal (i.e., r ₁ is the approximate radius of curvature of the jet) and λ₁,λ₂ are the internal Rossby radii of deformation in the upper and lower fluids, respectively.

The no-topography experiments show that for a sufficiently small F, the particular value depending on Ro, the jet is stable for the duration of the experiment. For sufficiently large F, again as a function of Ro, the jet becomes unstable, exhibiting horizontal wave disturbances from modes three to seven. An Ro against F flow regime diagram is presented.

Experiments are then conducted in the presence of a bottom topography having constant cross-section and extending around a mid-radius of the dishpan. The axis of the topography is in the vicinity of the jet axis forced in the no-topography experiments and the crest of the topography is in the vicinity of the interface between the two fluids (i.e., the front associated with the jet). The experiments show that in all cases investigated the jet tends to be stabilized by the bottom topography. Experiments with the topography in place, but with the interface between the fluids being above the topography crest, are shown to be unstable but more irregular than their no-topography counterparts.

Various quantitative measurements of the jet are presented. It is shown, for example, that the jet Rossby number defined in terms of the fluid withdrawal rate from the tank. Q, can be well correlated with a dimensionless vorticity gradient, V_G , across the upper layer jet. This allows for an assessment of the stability characteristics of a jet based on a knowledge of V_G (which can be estimated given a jet profile) and F.  相似文献   

Geophysical constraints on mesozoic disruption of North China Craton by underplating‐triggered lower‐crust flow of the Archaean lithosphere     

Zhongjie Zhang  Yanghua Wang  Yangfan Deng  Lin Chen  Jing Wu  Jiwen Teng  Yun Chen  Weiming Fan  Giuliano Panza 《地学学报》2013,25(3):245-251

The mechanism of the disruption, both lithospheric thinning and oceanization of the commonly accepted long‐term‐stable Archaean craton, is still an open question. The available models, all imply a bottom to top process. With the construction of a 1660‐km‐long transect across the eastern North China Craton (NCC), we demonstrate that both the P‐wave velocity and density in the lowermost crust beneath the central section are significantly higher than in the corresponding parts of the south and north sections on the transect. These features are interpreted as geophysical signature of lower crustal underplating, which supplies sufficiently high gravitational potential energy to trigger lateral flow of the lower crust. This magma underplating‐triggered bilateral lower crust flow may facilitate the lithospheric thinning by means of asthenosphere upwelling and decompression melting, which infill the gap produced by the lower crust flow. The underplating‐triggered lower crustal flow can provide an alternative mechanism to explain the NCC lithosphere disruption, which highlights the crustal feedback to Archaean lithosphere disruption, from top to bottom.  相似文献   

Theoretical and experimental study of breaking wave on sloping bottoms     

Kuei-Sen Yang  Yang-Yih Chen  Meng-Syue Li  Hung-Chu Hsu 《中国海洋工程》2013,27(6):737-750

This paper studies the continuous evolution of breaking wave for the surface water waves propagating on a sloping beach. A Lagrangian asymptotic solution is derived. According to the solution coupled with the wave breaking criteria and the equations of water particles motion, the wave deformation and the continuous wave breaking processes for the progressive water waves propagating on a sloping bottom can be derived. A series of experiments are also conducted to compare with the theoretical solution. The results show that the present solution can reasonably describe the plunging or spilling wave breaking phenomenon.  相似文献   

On the relationship between historical land‐use change and water availability: the case of the lower Tarim River region in northwestern China     

T. Liu  H. Fang  P. Willems  A. M. Bao  X. Chen  F. Veroustraete  Q. H. Dong 《水文研究》2013,27(2):251-261

Natural ecosystems in the region of the lower Tarim River in northwestern China strongly deteriorated since the 1950s due to an expanding desertification. As a result, the downstream Tarim River reaches became permanently dry land. This historical evolution in land‐use change is typically the result of the anthropogenic impact on natural ecosystems. On the basis of a spatially distributed hydrological catchment model bidirectionally linked with a fully hydrodynamic MIKE11 river model, land‐use changes characterized by historical changes in leaf area index (LAI) of vegetation, as well as the evolution of irrigated surface areas, can be causally related to changes in water resources (groundwater storage and surface water resources). An increased surface area of irrigated (agricultural) land, together with a majority of inefficient irrigation methods, did lead to a strong increase of water resources consumption of the farmlands located in the upper Tarim River area. Evidently, this evolution influenced available water resources downstream in the Tarim basin. As a result, farmland has been gradually relocated to the upstream regions. This has led to reduced flows from the upper Tarim stream, which subsequently accelerated the dropping of the groundwater level downstream in the basin. This study moreover demonstrates that land surface biomass changes (cumulative LAI) along the lower Tarim River are strongly related to the changes in groundwater storage. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Multiple overpressure systems and their relationship with hydrocarbon accumulation in the Qikou Depression of the Bohai Bay Basin,China     

Xue‐Bin Du  Xi‐Nong Xie  Yong‐Chao Lu  Liang Zhang  Wei Peng  Yun‐Peng Li 《Geological Journal》2015,50(4):465-476

Pressure measurements using drill stem tests and estimates from log data calculation indicate that three vertically stacked regional pressure compartments exist in the Qikou Depression of Bohai Bay Basin, N. China. The compartments comprise hydrostatic, upper weak, and lower overpressure systems. Laterally, overpressure (pressure coefficient > 1.2) occurs in the deeper areas and weakens gradually from the centre to the margin of the depression. The accumulation of oil and gas exhibits the interesting characteristics of oil‐bearing layers above gas‐bearing layers in the Qikou Depression. The pattern can be accounted for by the evolution of overpressure system, the maturity process of the source rock and the main fault activity. In the late Dongying Formation (Ed, 30 Ma), the lower overpressure system began to form shape, and the hydrocarbon sources generated a large volume of oil. However, because there was no migration pathway, the oil only accumulated in the original strata. In the late Guantao Formation (Ng, 12 Ma), the gas was generated, the upper overpressure system formed gradually, and the activity of the main fault gradually increased. Then, the overpressure pushed the early gathered oil to flow from the lower overpressure system into the upper overpressure system. Afterwards, the activity of the main fault decreased again and remains weak until now. Thus, later generated natural gas cannot keep migrating along the main fault and can only accumulate in the lower overpressure system. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

局部区域模型重力异常快速算法     

邢志斌  李姗姗  曲政豪  王伟  范昊鹏  贾鲁 《测绘科学技术学报》2016,(6):566-571

地球重力场位系数模型可以用于计算局部重力扰动场元。然而随着地球重力场模型阶次的提高、局域重力场计算范围的增大,其计算速度往往不能满足工程需求。针对这一问题,在对位系数模型泰勒级数展开的基础上提出了采用向量运算、混合编程的方法,同时对连带勒让德函数Belikov递推方法中与经纬度无关的量进行了预先计算,有效提高了计算速度。提出的方法对于利用超高阶次重力场模型快速解算大范围、高分辨率重力场元数据以及累加求和计算具有一定的参考与借鉴意义。  相似文献   

Estimation from Soil Temperature of Soil Thermal Diffusivity and Heat Flux in Sub-surface Layers   总被引：3，自引：0，他引：3  

Kedong An  Wenke Wang  Yaqian Zhao  Wenfeng Huang  Li Chen  Zaiyong Zhang  Qiangmin Wang  Wanxin Li 《Boundary-Layer Meteorology》2016,158(3):473-488

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Engagement in the Third U.S. National Climate Assessment: commitment,capacity, and communication for impact     

Emily Cloyd  Susanne C. Moser  Edward Maibach  Julie Maldonado  Tinqiao Chen 《Climatic change》2016,136(1):39-55

This paper examines the dynamics of energy investments and clean energy Research and Development (R&D) using a scenario-based modeling approach. Starting from the global scenarios proposed in the RoSE model ensemble experiment, we analyze the dynamics of investments under different assumptions regarding economic and population growth as well as availability of fossil fuel resources, in the absence of a climate policy. Our analysis indicates that economic growth and the speed of income convergence across countries matters for improvements in energy efficiency, both via dedicated R&D investments but mostly through capital-energy substitution. In contrast, fossil fuel prices, by changing the relative competitiveness of energy sources, create an economic opportunity for radical innovation in the energy sector. Indeed, our results suggest that fossil fuel availability is the key driver of investments in low carbon energy innovation. However, this innovation, by itself, is not sufficient to induce emission reductions compatible with climate stabilization objectives.  相似文献