共查询到20条相似文献，搜索用时 15 毫秒
1.
关于地下水变密度流与溶质运移的研究通常局限于二维系统中,三维系统中的研究非常有限。然而,仍有零星研究表明,三维系统中的对流过程与二维系统不同。文章通过SEAWAT-2000进行数值模拟,系统研究了二维和三维系统中的变密度溶质运移过程,利用舍伍德数、空间矩和稀释指数量化了系统的不稳定性和溶质扩散、稀释程度。结果表明:二维系统产生分散指流,而三维系统中因扩散程度的增强使得分散指流的产生受到抑制,但是,三维系统的不稳定性比二维系统更强,对流入渗更快,与指流的产生与否并无直接关联。另外,三维系统中溶质的稀释程度大于二维系统,但溶质在二维系统中将更快接近稀释的最大值,传统二阶中心矩可能会造成自由对流和不稳定性溶质运移过程中溶质扩散和稀释程度的错误估计。研究结果将有助于正确预测三维自然含水层中的自由对流和溶质运移。 相似文献
2.
海水入侵是困扰沿海地区经济社会发展的重大资源、环境问题,严重影响沿海地区地下水资源。定量模拟、预测和可视化管理是对海水入侵进行有效监测和机理分析的重要手段。基于前期海水入侵模拟的理论研究及方法,提出了海水入侵模拟及预测模型VFT3D,该模型综合考虑地表水-地下水对海水入侵的协同控制作用,能够模拟变密度地下水流及复杂反应性迁移,实现模拟海水入侵的完整水文循环过程。文章介绍了VFT3D模型,利用VFT3D模型模拟了一个海水入侵案例,并与SEAWAT模型模拟结果进行了对比分析。结果表明VFT3D 模型模拟水头与SEAWAT模型模拟结果相差不大,但SEAWAT模型无法模拟海水入侵中复杂的化学反应过程。VFT3D 模型模拟发现,水文地球化学过程（阳离子吸附交换作用）对阳离子（Na+、K+、Mg2+和Ca2+）运移产生明显影响,同时引起过渡带中离子组分浓度发生变化,对海水入侵过程产生较大影响。因此,考虑变密度和复杂反应过程,才能更加准确地描述海水入侵,从而有利于地下咸水治理工程的科学实施。 相似文献
3.
Visualizing complex pore structure and fluid flow in porous media using 3D printing technology and LBM simulation 
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下载免费PDF全文 Pore structures of porous media and properties of fluid flow are key factors for the study of non-Darcy groundwater flow. However, it is difficult to directly observe pore structures and flow properties, resulting in a “black box” problem of porous media. This problem has hindered the in-depth study of the groundwater flow mechanism at the pore scale. In recent years, 3D rapid prototyping technology has seen tremendous development. 3D printing provides digital models and printing models of porous media with clear internal structure. Thus, Lattice Boltzmann Method can be used to simulate the flow processes at the pore scale based on real pore structures. In this study, 3D printing cores and Lattice Boltzmann Method were coupled to conduct both laboratory and numerical experiments in spherical porous media with different sphere diameters and periodic arrays. The LBM simulation results show a good agreement with laboratory experimental results. With the advantages of LBM and 3D printing, this approach provides a visualization of the complex pore structure and fluid flow in pores, which is a promising method for studies of non-Darcy groundwater flow at the pore scale. 相似文献
4.
Free thermal convection and mixed convection are considered as potential mechanisms for mass and heat transport in sedimentary
basins. Mixed convection occurs when horizontal flows (forced convection) are superimposed on thermally driven flows. In cross
section, mixed convection is characterized by convection cells that migrate laterally in the direction of forced convective
flow. Two-dimensional finite-element simulations of variable-density groundwater flow and heat transport in a horizontal porous
layer were performed to determine critical mean Rayleigh numbers for the onset of free convection, using both isothermal and
semi-conductive boundaries. Additional simulations imposed a varying lateral fluid flux on the free-convection pattern. Results
from these experiments indicate that forced convection becomes dominant, completely eliminating buoyancy-driven circulation,
when the total forced-convection fluid flux exceeds the total flux possible due to free convection. Calculations of the thermal
rock alteration index (RAI=q·∇T) delineate the patterns of potential diagenesis produced by fluid movement through temperature gradients. Free convection
produces a distinct pattern of alternating positive and negative RAIs, whereas mixed convection produces a simpler layering
of positive and negative values and in general less diagenetic alteration.
Received, January 1999/Revised, June 1999/Accepted, July 1999 相似文献
5.
Challenges in reservoir forecasting 总被引：3，自引：0，他引：3
The combination of geostatistics-based numerical geological models and finite difference flow simulation has improved our ability to predict reservoir performance. The main contribution of geostatistical modeling has been more realistic representations of reservoir heterogeneity. Our understanding of the physics of fluid flow in porous media is reasonably captured by flow simulators in common usage. Notwithstanding the increasing application and success of geostatistics and flow simulation there remain many important challenges in reservoir forecasting. This application has alerted geoscientists and physicists that geostatistical/flow models in many respects, are, engineering approximations to thereal spatial distribution andreal flow processes. This paper reviews current research directions and presents some new ideas of where reserach could be focused to improve our ability to model geological features, model flow processes, and, ultimately, improve reservoir performance predictions. 相似文献
6.
Fast 3D Reservoir Simulation and Scale Up Using Streamtubes 总被引：1，自引：0，他引：1
This paper presents an implementation of a semianalytical method for oil recovery calculation in heterogeneous reservoirs that is both fast and accurate. The method defines streamline paths based on a conventional single-phase incompressible flow calculation. By calculating the time-of-flight for a particle along a streamline and assigning a volumetric flux to each streamline, the cumulative pore volume of a streamtube containing the streamline can be calculated. Subsequently, the streamtube geometries are kept constant and the effects of the time varying mobility distribution in two-phase flow are accounted for by varying the flow rate in each streamtube, based on fluid resistance changes along the streamtube. Oil recovery calculations are then done based on the 1D analytical Buckley–Leverett solution. This concept makes the method extremely fast and easy to implement, making it ideal to simulate large reservoirs generated by geostatiscal methods. The simulation results of a 3D heterogeneous reservoir are presented and compared with those of other simulators. The results shows that the new simulator is much faster than a traditional finite difference simulator, while having the same accuracy. The method also naturally handles the upscaling of absolute and relative permeability. We make use of these upscaling abilities to generate a coarse curvilinear grid that can be used in conventional simulators with a great advantage over conventional upscaled Cartesian grids. This paper also shows an upscaling example using this technique. 相似文献
7.
Tatiana Diniz Gonçalves Thomas Fischer Agnes Gräbe Olaf Kolditz Holger Weiss 《Environmental Earth Sciences》2013,69(2):617-631
In order to understand the groundwater dynamics and to improve the management of water resources in the Federal District of Brazil, this research proposes a 3D groundwater flow model to represent the groundwater level and flow system. The selected test site was the Pipiripau catchment. The development of the model was based on available geological, hydrogeological, geomorphological, climatological and pedological data. Geological and hydrogeological data were used to generate the 3D groundwater flow model. The 3D mesh elements of the domain were generated through the Groundwater Modeling System software, based on the logs of the well materials. The numerical simulation of the finite element method was implemented in the framework of the scientific software OpenGeoSys. With the 3D mesh-appropriated boundary conditions, annual average infiltration data and hydrogeological parameters were incorporated. Afterwards, the steady-state model was calibrated by the PEST software using available data of the water level from wells. The results showed the distribution of the steady-state hydraulic heads in the model domain, where the highest values occurred in the east and west recharge areas and the lowest values were found in the southwest of the basin. The results of this study can be a used as initial condition for the transient groundwater flow simulation and to provide a scientific basis for water resource management. 相似文献
8.
Pore-scale models are becoming increasingly useful as predictive tools for modeling flow and transport in porous media. These
models can accurately represent the 3D pore-structure of real media. Currently first-principles modeling methods are being
employed for obtaining qualitative and quantitative behavior. Generally, artificial, simple boundary conditions are imposed
on a model that is used as a stand-alone tool for extracting macroscopic parameters. However, realistic boundary conditions,
reflecting flow and transport in surrounding media, may be necessary for behavior that occurs over larger length scales or
including pore-scale models in a multiscale setting. Here, pore-scale network models are coupled to adjacent media (additional
pore-scale or continuum-scale models) using mortars. Mortars are 2D finite-element spaces employed to couple independent subdomains
by enforcing continuity of pressure and flux at shared boundary interfaces. While mortars have been used in the past to couple
subdomains of different models, physics, and meshes, they are extended here for the first time to pore-scale models. The approach
is demonstrated by modeling single-phase flow in coupled pore-scale models, but the methodology can be utilized to model dynamic
processes and perform multiscale modeling in 3D continuum simulators for flow and transport. 相似文献
9.
Thermo-hydro-mechanical modeling of carbon dioxide injection for enhanced gas-recovery (CO2-EGR): a benchmarking study for code comparison 总被引：2，自引：1，他引：1
Zhengmeng Hou Yang Gou Joshua Taron Uwe Jens Gorke Olaf Kolditz 《Environmental Earth Sciences》2012,67(2):549-561
The objective of this paper was to investigate the THM-coupled responses of the storage formation and caprock, induced by gas production, CO2-EGR (enhanced gas recovery), and CO2-storage. A generic 3D planer model (20,000?×?3,000?×?100?m, consisting of 1,200?m overburden, 100?m caprock, 200?m gas reservoir, and 1,500?m base rock) is adopted for the simulation process using the integrated code TOUGH2/EOS7C-FLAC3D and the multi-purpose simulator OpenGeoSys. Both simulators agree that the CO2-EGR phase under a balanced injection rate (31,500?tons/year) will cause almost no change in the reservoir pressure. The gas recovery rate increases 1.4?% in the 5-year CO2-EGR phase, and a better EGR effect could be achieved by increasing the distance between injection and production wells (e.g., 5.83?% for 5?km distance, instead of 1.2?km in this study). Under the considered conditions there is no evidence of plastic deformation and both reservoir and caprock behave elastically at all operation stages. The stress path could be predicted analytically and the results show that the isotropic and extensional stress regime will switch to the compressional stress regime, when the pore pressure rises to a specific level. Both simulators agree regarding modification of the reservoir stress state. With further CO2-injection tension failure in reservoir could occur, but shear failure will never happen under these conditions. Using TOUGH-FLAC, a scenario case is also analyzed with the assumption that the reservoir is naturally fractured. The specific analysis shows that the maximal storage pressure is 13.6?MPa which is determined by the penetration criterion of the caprock. 相似文献
10.
Using sand tank experiments and numerical models, local-scale solute-transport processes associated with free convection in both the region surrounding as well as within discrete low-permeability strata are explored. Different permeability geometries and contrasts between high- and low-permeability regions are tested. Results show that two free convective processes occur at different spatial and temporal scales. In the high-permeability region, salinisation was rapid and occurred predominantly by free convective flow around the low-permeability blocks (interlayer convection). A free convection flow field also became concurrently established within the low-permeability lenses (intralayer convection). It was found that upward vertical flow created by the large-scale interlayer free-convective flow field in the high-permeability region retards salinisation of the lenses as buoyant freshwater displacements oppose the downward penetration of dissolved salts. Salinisation of the low-permeability structures eventually takes place from below as saltwater is dragged upwards. This bottom up convective salinisation process of low permeability strata has not been reported in previous literature. These results demonstrate that variable-density sequestration of solutes driven by a source resident above the low-permeability layer is a complicated function of the geometry of the permeability distribution and the permeability contrast between low- and high-permeability regions. 相似文献
11.
We present the results of a study on a posteriori error control strategies for finite volume element approximations of second order elliptic differential equations. Finite volume methods ensure local mass conservation and, combined with some up-wind strategies, give monotone solutions. We adapt the local refinement techniques known from the finite element method to the finite volume discretizations of various boundary value problems for steady-state convection–diffusion–reaction equations. In this paper we derive and study a residual type error estimator and illustrate its practical performance on a series of computational tests in 2 and 3 dimensions. Our tests show that the discussed locally conservative approximation methods with a posteriori error control can be used successfully in numerical simulation of fluid flow and transport in porous media. 相似文献
12.
Ina Spottke Eric Zechner Peter Huggenberger 《International Journal of Earth Sciences》2005,94(4):580-593
A 3D geological model of the area east of Basel on the southeastern border of the Upper Rhine Graben, consisting of 47 faults and six stratigraphic horizons relevant for groundwater flow, was developed using borehole data, geological maps, geological cross sections, and outcrop data. This model provides new insight into the discussions about the kinematics of the area between the southeastern border of the Upper Rhine Graben and the Tabular Jura east of Basel. A 3D analysis showed that both thin-skinned and thick-skinned tectonic elements occur in the modeled area and that the Anticline and a series of narrow graben structures developed simultaneously during an extensional stress-field varying from E–W to SSE–NNW, which lasted from the Middle Eocene to Late Oligocene. In a new approach the faults and horizons of the 3D geological model were transferred into discrete elements with distributed hydrogeological properties in order to simulate the 3D groundwater flow regime within the modeled aquifers. A three-layer approach with a horizontal regularly spaced grid combined with an irregular property distribution of transmissivity in depth permitted the piezometric head of the steady-state model to be automatically calibrated to corresponding measurements using more than 200 piezometers. Groundwater modeling results demonstrated that large-scale industrial pumping affected the groundwater flow field in the Upper Muschelkalk aquifer at distances of up to 2 km to the south. The results of this research will act as the basis for further model developments, including salt dissolution and solute transport in the area, and may ultimately help to provide predictions for widespread land subsidence risks. 相似文献
13.
数值模拟法是地下水水量和水质评价的主要技术方法,通过简述地下水数值模拟的发展历程、FEFLOW软件的输入特点和功能,并结合FEFLOW在地下水模拟方面的应用现状,论述了对河流和断层处理的方法,最后提出了FEFLOW软件存在的问题及应用前景。研究结果可知:(1) FEFLOW是迄今为止功能最为齐全的地下水数值模拟软件,适用于各种尺度的地下水、多孔介质和热能传输项目,但这些领域基本都是水流和溶质运移耦合、水流和热量运移耦合等两场进行耦合,少见三场耦合研究实例;(2)存在无法实现源汇项单独处理等缺陷,仅能实现in/outflow on top/bottom菜单功能,降雨入渗和蒸发同时作用必须用净补给量来表达,增加了前处理的困难,在应用模型模拟时,由于FEFLOW网格划分时的数量受到限制,超大区域建模也容易出现不精确问题;(3)在对地下水污染物运移模型模拟时,通常考虑的是对流、弥散、吸附作用,而未有一阶化学非平衡反应,随着人类对地下水环境和质量的高度重视,对于两相有机和无机污染物迁移耦合研究将会是未来的研究重点。 相似文献
14.
Pedro A. L. P. Firme Nuno B. Brandao Deane Roehl Celso Romanel 《Acta Geotechnica》2018,13(6):1329-1340
The double-mechanism creep law (DM model) is an empirical creep constitutive model widely employed in Brazilian salt rock mechanics. This model often presents good performance in steady-state creep prediction. However, transient creep is not accounted for, and whenever early creep estimates are important, the contribution of this phase might be meaningful. This work adds value by presenting two alternatives to account for transient creep in the DM model. The first alternative couples the transient function from Sandia’s multi-mechanism deformation model to the DM model steady-state creep rate (EDMT model). The second alternative couples the DM model response to Norton’s power law when the strain rate given by the latter remains lower than the one from the former (EDMP model). These models can be implemented in numerical simulators at small code extensions of the DM model implementations. Applications from previous works by the authors are revisited to validate the formulations based on experimental data. EDMT and EDMP models differ in the formulation of transient creep and, consequently, in the time of transition between the transient and the steady-state phases. Both methods were successful in treating transient creep and in simulating experimental results. 相似文献
15.
在防止土壤侵蚀和雨后抑制蒸发的条件下,利用室内模拟降雨试验,研究了上方来水对坡面降雨入渗、湿润锋运移以及土壤水分再分布的影响。结果表明:对于初始含水量很低的土壤,与上方无来水相比,上方来水时降雨入渗过程中入渗率有一个上升的阶段,但平均入渗率反而降低;在降雨入渗初期,由于上方来水的沿程入渗,上方来水对坡面湿润锋运移的影响较大,但随后几乎没有影响,湿润锋的运移主要与基质势梯度有关;土壤水分沿坡面呈"波浪形"分布是坡面径流的波动性、上方来水(径流)的沿程入渗以及侧向沿坡向下流等综合作用的结果。 相似文献
16.
Theoretical and numerical analyses of convective instability in porous media with upward throughflow
Exact analytical solutions have been obtained for a hydrothermal system consisting of a horizontal porous layer with upward throughflow. The boundary conditions considered are constant temperature, constant pressure at the top, and constant vertical temperature gradient, constant Darcy velocity at the bottom of the layer. After deriving the exact analytical solutions, we examine the stability of the solutions using linear stability theory and the Galerkin method. It has been found that the exact solutions for such a hydrothermal system become unstable when the Rayleigh number of the system is equal to or greater than the corresponding critical Rayleigh number. For small and moderate Peclet numbers (Pe ⩽ 6), an increase in upward throughflow destabilizes the convective flow in the horizontal layer. To confirm these findings, the finite element method with the progressive asymptotic approach procedure is used to compute the convective cells in such a hydrothermal system. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
17.
The aim of this paper is to present a three‐dimensional (3D) finite element modeling of heat and mass transfer phenomena in partially saturated open porous media with random fields of material properties. Randomness leads to transfer processes within the porous medium that naturally need a full 3D modeling for any quantitative assessment of these processes. Nevertheless, the counterpart of 3D modeling is a significant increase in computations cost. Therefore, a staggered solution strategy is adopted which permits to solve the equations sequentially. This appropriate partitioning reduces the size of the discretized problem to be solved at each time step. It is based on a specific iterative algorithm to account for the interaction between all the transfer processes. Accordingly, a suitable linearization of mass convective boundary conditions, consistent with the staggered algorithm, is also derived. After some validation tests, the 3D numerical model is used for studying the drying process of a cementitious material with regard to its intrinsic permeability randomness. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
18.
K. Johannsen 《Computational Geosciences》2003,7(3):169-182
The Elder problem is an example of a density driven flow, motivated by experiments of a thermally driven convection in porous media. It is a mathematical benchmark problem used for code verification of density driven flow simulators and comparison of issues related to its numerical treatment. Its bifurcation diagram with respect to the Rayleigh number is investigated on a hierarchy of uniformly refined grids. Eleven stationary solutions are shown to exist for the Elder problem. Similar solutions can be found using the Boussinesq approximation. Despite this similarity the corresponding bifurcation diagrams are shown to be topologically not equivalent. This gives rise to serious doubts on the validity of Boussinesq approximation for this model problem. Grid convergence is investigated for the numerically obtained solutions. 相似文献
19.
A novel two-dimensional mixed fracture–pore seepage model for fluid flow in fractured porous media is presented based on the computational framework of finite-discrete element method (FDEM). The model consists of a porous seepage model in triangular elements bonded by unbroken joint elements, as well as a fracture seepage model in broken joint elements. The principle for determining the fluid exchange coefficient of the unbroken joint element is provided to ensure numerical accuracy and efficiency. The mixed fracture–pore seepage model provides a simple but effective tool for solving fluid flow in fractured porous media. In this paper, examples of 1D and 2D seepage flow in porous media and porous media with a single fracture or multiple fractures are studied. The simulation results of the model match well with theoretical solutions or results obtained by commercial software, which verifies the correctness of the mixed fracture–pore seepage model. Furthermore, combining FDEM mechanical calculation and the mixed fracture–pore seepage model, a coupled hydromechanical model is built to simulate fluid-driven dynamic propagation of cracks in the porous media, as well as its influence on pore seepage and fracture seepage.
相似文献20.
煤矿开采面临的水文地质条件越来越复杂,尤其是遭遇承压含水层的水压力越来越大,突水灾害发生时必然会带来高水力梯度引起的破碎岩体突水通道内高速非线性渗流问题。据此,研制高水力梯度（最大600）条件下堆积型多孔介质中高速非线性渗流试验装置,采用堆积型钢球模拟破碎岩体,对粒径为1、2、3、4、5、6 mm共6种光滑钢球分别开展了一维均质圆柱渗流试验。试验结果表明：对于由1～6 mm钢球堆积而成的孔隙率为0.44～0.45的多孔介质,当水力梯度大于145时,通过分析水力梯度-平均流速（J-v）曲线和水力梯度-雷诺数（J-Re）关系曲线,将流动状态划分为3个模式：线性层流、非线性层流、紊流,并获得了从线性层流过渡到非线性层流的临界流速为0.23～0.78 cm/s、临界水力梯度为3～8;从层流到紊流转捩的临界流速为1.6～4.8 cm/s、临界水力梯度为90～145。从小粒径多孔介质到大粒径多孔介质的渗流过程中,临界流速越来越大,而临界水力梯度逐渐减小。 渗透率与粒径的平方、非达西流影响系数与粒径的倒数均呈线性正相关,非达西流影响系数随着渗透率的增加呈指数减小。该研究对多孔介质非线性渗流的理论研究以及实际工程中高承压含水层突涌水问题有重要借鉴意义。 相似文献