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1.
Three-phase numerical model of water migration in partially frozen geological media: model formulation,validation, and applications 总被引:3,自引:0,他引:3
Scott L. Painter 《Computational Geosciences》2011,15(1):69-85
Water in the subsurface of the Earth’s cold regions—and possibly the subsurface of Mars—resides in the liquid, vapor, and
ice phases. However, relatively few simulations addressing full three-phase, nonisothermal water dynamics in below-freezing
porous media have been undertaken. This paper presents a nonisothermal, three-phase approach to modeling water migration in
partially frozen porous media. Conservation equations for water (as ice, liquid, and vapor) and a single gas species (in the
gas phase and dissolved in water) are coupled to a heat transport equation and solved by a finite-volume method with fully
implicit time stepping. Particular attention is given to the method of spatial differencing when the pore space is partially
filled with ice. The numerical model is able to reproduce freezing-induced water redistribution observed in laboratory experiments.
Simulations of Earth permafrost dynamics and of the formation and evolution of a planetary-scale cryosphere on Mars demonstrate
the new capabilities. 相似文献
2.
Non-isothermal flow in low permeable porous media: a comparison of Richards’ and two-phase flow approaches 总被引:1,自引:1,他引:0
Wenqing Wang Jonny Rutqvist Uwe-Jens Görke Jens T. Birkholzer Olaf Kolditz 《Environmental Earth Sciences》2011,62(6):1197-1207
The present work compares the performance of two alternative flow models for the simulation of thermal-hydraulic coupled processes
in low permeable porous media: non-isothermal Richards’ and two-phase flow concepts. Both models take vaporization processes
into account: however, the Richards’ model neglects dynamic pressure variations and bulk flow of the gaseous phase. For the
comparison of the two approaches first published, data from a laboratory experiment are studied involving thermally driven
moisture flow in a partially saturated bentonite sample. Then a benchmark test of longer-term thermal-hydraulic behavior in
the engineered barrier system of a geological nuclear waste repository is analyzed (DECOVALEX project). It was found that
both models can be used to reproduce the vaporization process if the intrinsic permeability is relative high. However, when
a thermal-hydraulic coupled problem has the same low intrinsic permeability, only the two-phase flow approach provides reasonable
results. 相似文献
3.
The multiphase flow simulator moving particle semi-implicit (MPS) method is developed based on the fractional-flow approach,
originated in the petroleum engineering literature, considering the fully three-phase flow with general boundary conditions.
The fractional flow approach employs water saturation, total liquid saturation, and total pressure as primary variables. Most
existing models based upon fractional flow are limited to two-phase flow and specific boundary conditions. Although there
appear a number of three-phase flow models, they were mostly developed using pressure-based approaches, which require variable-switch
techniques to deal with phase appearance and disappearance. The use of fractional flow-based approaches in MPS makes it unnecessary
to use variable-switching to handle the change of phase configurations because the water saturation, total liquid saturation,
and total pressure exist throughout the solution domain regardless of whether certain phases are present or not. Furthermore,
most existing fractional flow-based models consider only specific boundary conditions, usually Dirichlet-type pressure for
water phase and flux-type boundary for nonaqueous phase liquid or particular combinations for individual phase. However, the
present model considers general boundary conditions of ten most possible and plausible cases. The first eight cases are the
combinations of the phase pressure or the phase flux of each of the three individual phases. The other two cases are the variable
boundary conditions: one for water-medium interface and the other for the air-medium interface when the directions of fluxes
are not known a priori. Thus, the model’s capabilities of handling general boundary conditions extend the simulators’ usefulness
in the field system. 相似文献
4.
Sudhakar M. Rao B. V. Venkatarama Reddy 《Geotechnical and Geological Engineering》2006,24(6):1545-1559
The gold mining process at Kolar gold field (KGF) mines has generated about 32 million tons of tailings. Gold was extracted
from the mined ores using cyanidation technique that involved dissolution of gold in the ore by water soluble alkali metal
cyanides (example, sodium cyanide or potassium cyanide). Of the several dumps that received the mine tailings only the Kennedy’s
Line dump was active prior to closure of the KGF mines in the year 2000. The Kennedy’s Line dump received sulfide bearing
tailings in slurry form that comprised of spent ore and process water bearing soluble alkali metal cyanide. Depending on the
pH of the tailing slurry, the free cyanides may exist as aqueous hydrogen cyanide that can escape to the atmosphere as hydrogen
cyanide gas or occur as soluble cyanide (CN−) ions that can be leached by infiltrating water to the sub-surface environment. Additionally, the presence of pyrite minerals
in the Kennedy’s Line dump makes them susceptible to acid drainage. This study examines the potential of gold tailings of
Kennedy’s Line dump to release cyanide ions (CN−) and acid drainage to the sub-surface environment by performing physico-chemical and leaching tests with tailing samples
collected from various depths of the dump, sub-surface soil samples beneath the dump and groundwater samples from vicinity
of Kennedy’s Line dump. The chemical mechanisms responsible for the ambient cyanide and pH levels of the tailing dump, sub-surface
soil samples and groundwater are also inferred from the laboratory results. 相似文献
5.
6.
The water column flow velocity of 36 river sections in the river reach between Hankou (Wuhan) and Wuxue of the middle-lower
Changjiang River. Their cross sectional distribution patterns in relation to the river channel morphologies were examined
by using ship-mounted ADCP (Acoustic Doppler Current Profiler) instrument. The results indicate four (I-VI) types of river
channel morphology associated flow patterns: I—laterally deepening riverbed topographic pattern; II—symmetrical to asymmetrical
riverbed topographic pattern; III—relative flat riverbed topographic pattern, and IV—sandbar supported riverbed topographic
pattern. All these correspond to the different patterns of flow velocity distribution. The maximum flow velocity is usually
related to the deeper water depth, but irregular water column distribution of flow current velocity results often from the
vortices’ current associated with river knots. Deeper river water depth is usually identified in the river reach located slightly
downstream to the river knot, where faster flow velocity occurs. Downward change in flow velocity fits semi-log law, showing
an exponential decreasing flow current with the maximum flow velocity near the water surface. However, in the river reach
near the river knots, the water column distribution of flow current velocity does not fit the semi-log law, showing the irregular
flow current pattern. This study, in context of river catchment management, highlights the controls of riverbed morphology
to the flow current structure, which will shed light on the post study of Three Gorges damming in 2009. 相似文献
7.
We derive a new formulation for the compositional compressible two-phase flow in porous media. We consider a liquid–gas system with two components: water and hydrogen. The formulation considers gravity, capillary effects, and diffusivity of each component. The main feature of this formulation is the introduction of the global pressure variable that partially decouples the system equations. To formulate the final system, and in order to avoid primary unknowns changing between one-phase and two-phase zones, a second persistent variable is introduced: the total hydrogen mass density. The derived system is written in terms of the global pressure and the total hydrogen mass density. The system is capable of modeling the flows in both one and two-phase zones with no changes of the primary unknowns. The mathematical structure is well defined: the system consists of two nonlinear parabolic equations, the global pressure equation, and the total hydrogen mass density equation. The derived formulation is fully equivalent to the original one. Numerical simulations show ability of this new formulation to model efficiently the phase appearance and disappearance. 相似文献
8.
In this paper the ability of analytical solutions for four-component three-phase flow to predict displacement efficiency in
water alternating gas (WAG) injection processes is studied. First analytical solutions for Riemann problems with injection
compositions that are the average water and gas mixture for various WAG injection schemes are presented. These solutions are
compared to numerical calculations with variable slug sizes and used to explore the effect of slug size, injecting water vs
gas first, and the average injection composition on displacement efficiency in compositional WAG schemes. The example model
is partially miscible WAG injection of water and CO2 into an oil reservoir containing C10 and CH4 with and without a mobile aqueous phase present initially. The trailing end of the water and gas profiles are sensitive to
whether water or gas is injected first, but the magnitude of the oil bank and the breakthrough time of the injected fluids
are accurately predicted by the analytical solutions, even for displacements where large water and gas slugs are injected.
Fluctuations in the saturation and composition profiles resulting from the alternating injection sequence in the WAG simulations
appear as super-imposed on top of the sequence of rarefaction and shock waves predicted by analytical solutions. As the number
of slugs increases, the effect of alternating boundary conditions diminishes and the displacements predicted by numerical
calculations converge to the analytical solutions. 相似文献
9.
考虑气相影响的降雨入渗过程分析研究 总被引:4,自引:1,他引:3
降雨入渗过程是水在下渗的过程中驱替空气的水-气二相流过程,对这一过程的精确模拟一直是渗流计算的难点,目前的处理方法通常是忽略孔隙气压力变化的影响。根据多相流理论,结合质量守恒定律和达西定律,建立了水-气二相流模型,模型的求解采用积分有限差分法和Newton-Raphson迭代方法,通过变换主要变量来表达相态的变化,实现了水相、气相边界条件及降雨入渗边界的精确模拟。利用上述模型对一土柱试验进行模拟,从而验证了模型的正确性,研究了一均质土层的降雨入渗过程,得到了孔隙水压力、孔隙气压力和毛细压力及含水率的变化过程。根据入渗率与地表孔隙气压力的变化关系,验证了孔隙气压力的增大对入渗水流产生阻滞作用。在求解非稳定渗流问题中,考虑空气压力变化的影响是值得研究的。 相似文献
10.
To better understand the movement and transport of water and pollution through the coarse gravel unsaturated zone, the presented
research was conducted to estimate water flow and transport processes with a tracing experiment in a lysimeter in the Selniška
Dobrava. A combined tracing experiment was performed with deuterated water and the fluorescent dye—uranine. The fastest and
dominant flow velocities were calculated based on injection time, the first tracer appearance time and the time of highest
concentration. Mean flow velocity and vertical dispersion were estimated by an analytical best-fit method using one-dimensional
convection–dispersion model. Deuterium was confirmed as an ideal conservative tracer and a more suitable tracer than dye (uranine)
for the study of water flow in the unsaturated zone of a coarse gravel aquifer. The retardation factor of the dye as compared
with deuterium was 1.13–1.75, which is in agreement with previously published results. Artificial tracers, especially deuterated
water, were also identified as a very useful tool to assess other properties and differences in water flow in the unsaturated
zone of a coarse gravel aquifer such as velocity and dispersion. 相似文献
11.
We consider the modeling and simulation of compositional two-phase flow in a porous medium, where one phase is allowed to
vanish or appear. The modeling of Marchand et al. (in review) leads to a nonlinear system of two conservation equations. Each
conservation equation contains several nonlinear diffusion terms, which in general cannot be written as a function of the
gradients of the two principal unknowns. Also the diffusion coefficients are not necessarily explicit local functions of them.
For the generalised mixed finite elements approximation, Lagrange multipliers associated to each principal unknown are introduced,
the sum of the diffusive fluxes of each component is explicitly eliminated and the static condensation leads to a “global”
nonlinear system of equations only in the Lagrange multipliers also including complementarity conditions to cope with vanishing
or appearing phases. After time discretisation, this system can be solved at each time step using a semi-smooth Newton method.
The static condensation involves “local” nonlinear systems of equations associated to each element, solved also by a semismooth
Newton method. The algorithm is successfully applied to 1D and 2D examples of water–hydrogen flow involving gas phase appearance
and disappearance. 相似文献
12.
Hsien-Tang Tsai Cheng-Jui Tseng Shian-Yang Tzeng Tung-Ju Wu Jen-der Day 《Natural Hazards》2012,62(1):83-91
Typhoon Morakot hit Taiwan in 2009, severely damaging the Alishan National Forest Recreation Area, a famous tourist resort
in Taiwan. The only highway to this area was under repair for 10 months after the typhoon. Consequently, Alishan’s tourism
industry suffered losses estimated at NT$1 billion. This work investigates the impacts of natural hazards on Taiwan’s tourism
industry. First, government, university, and industry experts were invited to a focus-group interview to update criteria for
tourism development in Taiwan. Next, the Analytic Hierarchy Process (AHP) was applied to rank the proposed criteria. Last,
two tourist attractions, one urban and one rural, are discussed in detail. This work proposes three novel dimensions for Taiwan’s
tourism development—destination attraction, destination arrangement, and contingency planning for natural hazards—which comprise
nine criteria. Analytical results will provide Taiwan’s tourism industry with references for future policy-making and sustainable
development. 相似文献
13.
Several experimental methods have been proposed for consolidation test such as: constant loading rate, constant gradient and
constant rate of strain (CRS). Unfortunately, there are no unique criteria for performing the CRS consolidation test. Also,
there are considerable differences among the standards proposed for the test. In the present paper, authors have tried to
find the reasons for differences among standards, by studying the basic assumptions made on the characteristics of the pore
water flow during consolidation process. In the course of study, CRS consolidation tests were carried out under different
strain rates on remolded samples. The results of the tests have indicated that the Darcy’s law is not valid throughout the
CRS test and therefore, any consolidation equation based on Darcy’s law would not provide accurate results. The results of
the current experiments also showed that with regard to the applied strain rates, there are three different flow regimes governing
the process named as: pre-linear (non-Darcy flow), linear (Darcy flow) and post-linear (non-Darcy flow). Experimental results
also showed that distinction between boundaries of linear and nonlinear flow is possible from the excess pore pressure developed
during the tests. 相似文献
14.
The significant role of the drainage area’s geological background in the formation of the groundwater runoff in the active
water-exchange zone was revealed for the first time on the basis of long-term observations of streams of the Upper Kolyma
River region during the autumn-winter low-water period, when the rivers are fed only by the groundwater recharge. The analysis
of all the available data made it possible to define the characteristic periods in the autumn-winter low-water season. The
waters of the seasonally thawed layer play the dominant role in the river’s recharge in September; the suprapermafrost water,
in January; and the subgelisol water (nonfreezing water streams) during the 30-day-long period of the minimal flow. The quantitative
parameters of the groundwater runoff corresponding to its module during this period reflect the water influx to the active
water-exchange zone. It is established that the latter is minimal in the In’yali-Debin synclinorium, which consists of sedimentary
rocks formed in deepwater trough environments. Their subsequent transformation proceeded under the action of subduction-accretionary
and shear strains. The water availability in the active water-exchange in the Ayan-Yuryakh anticlinorium zone is substantially
higher, although the Late Paleozoic and Early Mesozoic sedimentary formations of this area were also deposited in deepwater
trough settings, but their subsequent evolution was related to the uplift of the anticlinorium. The maximal watering is observed
in the active water-exchange zone of the Omulevka terrane, which is composed of Paleozoic terrigenous-carbonate and carbonate
formations. The differences in the hydrogeological regimes of the terranes may be significant with respect to their geoecology. 相似文献
15.
The relatively slow flow and exchange of Carr Inlet water with the main basin of Puget Sound, Washington, favor eutrophication.
To study Carr Inlet’s circulation, the Model-measurement Integration Experiment in Estuary Dynamics (MIXED) was conducted
in March–May 2003, spanning the spring bloom. From observations and numerical simulations the circulation was decomposed into
tidal and subtidal components; the former was dominated by the M2 tide, the latter by atmospheric forcing. Near the surface,
the subtidal velocity was correlated with wind. At mid depths, the subtidal velocity was organized into vertical bands arising
from internal waves excited by wind forcing of the water surface. The tidal flow was more strongly steered by local bathymetry
and weaker in peak magnitudes than the subtidal flow, yet it contributed more mechanical energy to the inlet. Tidal eddies
reduce exchange of water through the inlet’s entrances. Numerical simulations with the Princeton Ocean Model recreated many
observed features, including the three-layer vertical structure of outflow at the surface and bottom and inflow at mid depth,
the mid-depth subtidal response to the wind, and characteristics of the tide. While the model produced greater subtidal flow
magnitudes at depth and differences in the phase of the M2 tide compared to observations, overall the case study provided
support for more comprehensive simulations of Puget Sound in the future. 相似文献
16.
非饱和带水气二相渗流动力学模型 总被引:3,自引:0,他引:3
非饱和带地下水运动实质上是一个水气二相渗流过程。本文以多相渗流理论为基础,从水气二相渗流的连续性方程和达西定律出发,推导了非饱和带水气二相渗流的耦合动力学模型,讨论了模型的IMPES和全隐式联立求解方法的原理和步骤,认为IMPES求解方法由于达西系数项的处理,饱和度的计算均采用显式,因此该解法具有稳定性差、精度低且要求计算时间步长小的局限性;而全隐式联立求解方法是联立求解气相、水相方程,同时求出压力和饱和度值,因此压力和饱和度值都是隐式求出,具有较高精度,且无条件稳定,应是今后模型求解的重点研究内容 相似文献
17.
Numerical simulation of gas migration driven by compressible two-phase partially miscible flow in porous media is of major importance for safety assessment of deep geological repositories for long-lived high-level nuclear waste. We present modeling of compositional liquid and gas flow for numerical simulations of hydrogen migration in deep geological radioactive waste repository based on persistent primary variables. Two-phase flow is considered, with incompressible liquid and compressible gas, which includes capillary effects, gas dissolution, and diffusivity. After discussing briefly the existing approaches to deal with phase appearance and disappearance problem, including a persistent set of variables already considered in a previous paper (Bourgeat et al., Comput Geosci 13(1):29–42, 2009), we focus on a new variant of the primary variables: dissolved hydrogen mass concentration and liquid pressure. This choice leads to a unique and consistent formulation in liquid saturated and unsaturated regions, which is well adapted to heterogeneous media. We use this new set of variable for numerical simulations and show computational evidences of its adequacy to simulate gas phase appearance and disappearance in different but typical situations for gas migration in an underground radioactive waste repository. 相似文献
18.
This paper combines analytical and numerical studies of light oil recovery by air injection. We investigate in detail the internal structure of oxidation fronts in two-phase flow in a porous medium, taking into account reaction, vaporization, and condensation of liquid fuel, with longitudinal heat conduction. Our solution shows that between regimes of total and partial oxygen consumption there is a change in the oxidation wave, which may have negative implications for oxygen breakthrough in light oil recovery process. In spite of the simplifications used to derive the analytical solution, the latter agrees with direct numerical simulations. Finally, based on our analytical solution, we provide a phase diagram to predict conditions for total or partial oxygen consumption in light oil recovery process. 相似文献
19.
库水位下降时的岸坡非稳定渗流问题研究 总被引:5,自引:1,他引:4
水位下降时岸坡的渗流是涉及土体由饱和向非饱和状态过渡的水-气二相流过程,目前相关研究成果大都假设孔隙气压力为0,忽略孔隙气的影响。根据水、空气的质量守恒定律和达西定律,结合多相流理论建立水-气二相流模型,采用高效的积分有限差分法求解,通过变换主要变量,实现饱和(单相)与非饱和(二相)的相互转变,并给出各种边界条件下合理的数学处理方法。通过Muskat渗流问题,验证了上述模型的正确性;并对某土质岸坡水位下降时的非稳定渗流问题进行分析,结果表明,岸坡的基质吸力小于浸润线以上的负孔隙水压力,在浸润线以上的很大区域为毛细管水饱和带,其土体饱和且基质吸力为0,这对边坡稳定十分不利,精确分析水位下降的边坡稳定问题时,孔隙气压力变化的影响值得研究。 相似文献
20.
Hamzah Muzaini 《GeoJournal》2006,66(3):211-222
Despite the salience of the Second World War in paving the way for Singapore to attain formal independent status in 1965,
it was not until the 1990s that war events were inserted into the state’s narratives, and ‘mapped’ onto its spaces as visible
national fodder to bind citizens together. Since then, memoryscapes in many forms have proliferated over the state’s cityscape.
After tracing the genesis of official war commemorative gestures within Singapore, the paper examines the ways in which Singaporeans
have responded to them. Specifically, the paper argues that, while Singaporeans recognize the importance of remembering the
war as nationally significant, this has not translated into any physical attempt or desire—beyond the discursive—to participate
in the state’s commemorative endeavours. In analyzing factors that may have hindered the actual bodily practice of war remembrance in Singapore, nationalized war memoryscapes are also seen as embodying numerous politics due
to tensions arising from a collision between what the state and its people perceive to be ideal means of remembering and representing
the war within national discourses in the context of the present. 相似文献