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61.
本文利用COMSOL软件建立轻非水相流体(LNAPL)纵向迁移转化模型,采用有限单元法进行求解,预测污染物分布规律,并利用局部分析法进行参数敏感性分析.结果表明,大部分LNAPL会在水面以上聚集形成高的质量分布峰值区域,少部分克服毛细压力向下迁移,在自由相迁移范围内,其溶解相浓度达到或接近饱和溶解度;当顶部污染源消失后,降水会使最大饱和度和浓度出现的深度逐渐下移;多孔介质中的低渗透镜体会使污染物垂向入渗受阻,在其表面聚积形成污染池;渗透系数是控制LNAPL纵向迁移速度及饱和度分布的关键参数. 相似文献
62.
The purpose of this study is to present a library of analytical solutions for the three-dimensional contaminant transport in uniform flow field in porous media with the first-order decay, linear sorption, and zero-order production. The library is constructed using Green’s function method (GFM) in combination with available solutions. The library covers a wide range of solutions for various conditions. The aquifer can be vertically finite, semi-infinitive or infinitive, and laterally semi-infinitive or infinitive. The geometry of the sources can be of point, line, plane or volumetric body; and the source release can be continuous, instantaneous, or by following a given function over time. Dimensionless forms of the solutions are also proposed. A computer code FlowCAS is developed to calculate the solutions. Calculated results demonstrate the correctness of the presented solutions. The library is widely applicable to solve contaminant transport problems of one- or multiple- dimensions in uniform flow fields. 相似文献
63.
The presence of an immobile gaseous phase in an otherwise-saturated porous medium affects the transport of volatile compounds. The linear theory of partitioning tracers suggests that a volatile tracer introduced into such a system should be retarded with a constant retardation factor. Using high concentrations, however, the saturation of the gaseous phase will change as an effect of the tracer test itself. Competitive gas transfer among all volatile compounds and the change of saturation may lead to tracer concentrations that are temporarily higher than those injected. We analyze the system in the framework of the coherence theory by Helfferich [Soc. Pet. Eng. J. 21 (1) (1981) 51]. The governing equations are formulated as functions of total concentration, i.e., the mass of solutes in all phases per pore volume. Neglecting dispersion and mass-transfer kinetics, we derive the characteristic form of the resulting system of hyperbolic equations. In a system with N volatile compounds, a variation of the concentrations splits up into N waves, each traveling with its own characteristic velocity. If the presence of a gaseous phase is sustained, one wave will be a standing one. We perform numerical model calculations for tracers with various Henry's law coefficients and show that the results agree with the semi-analytical solution obtained by coherence theory. 相似文献
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66.
为研究管道内金属丝网对甲烷/空气预混火焰传播的影响,通过实验和三维数值模拟研究安装金属丝网的管道内火焰传播特性以及流场、温度场的变化。结果表明:40目4层的金属丝网可以使火焰淬熄,30目4层的金属丝网无法淬熄,但可以使火焰停滞3 ms;大涡模型可以很好地对管道内火焰淬熄现象进行模拟;当火焰穿过30目4层金属丝网时,速度增大,在Kelvin Helmholtz不稳定和Rayleigh Taylor不稳定的耦合作用下形成湍流;金属丝网的目数会影响热量在丝网层中的扩散,当金属丝网为30目4层时,火焰热量扩散快,而当金属丝网为40目4层时,火焰热量扩散慢且温度大幅度衰减,衰减率达到83%。 相似文献
67.
Mark DeLaurier Michael Salvador 《Environmental Communication: A Journal of Nature and Culture》2018,12(3):387-401
This paper responds to recent calls for alternative approaches to the analysis of environmental communication that uncover overlooked voices in the discussion of environmental issues. Borrowing core principles from critical rhetoric, it suggests a way to categorize media messages according to how human–nature relationships are constructed in media discourse. The paper illustrates how, in presenting contrasting and often oppositional constructions of human–nature relationships, the media messages examined articulate three recurrent (but not equal) discourses on global warming. These discourses include (1) nature-as-out-of-reach discourse, (2) nature-as-antagonist discourse, and (3) nature-as-co-present discourse. By juxtaposing these discourses, the paper shows how environmental communication scholars can engage in critical realism and political advocacy to illuminate latent public discourse that holds the potential to champion marginalized voices of nature and accentuate the interconnectedness of humans and the environment. 相似文献
68.
以动态生成的CaO孔隙网络为骨架,按照不退行随机行走模型(NRRW),模拟气体分子在CaO孔隙中的扩散过程,计算了SO2分子的扩散系数和行走维数,并在SO2非线性扩散反应方程基础上,分析了CaO颗粒孔隙中SO2浓度的分布特性。 相似文献
69.
建立潜流湿地有机污染物迁移转化模型,采用多孔介质模型描述潜流湿地的水力特性,并引入Monod方程相耦合,实现对湿地系统内部流场及水质浓度的同时模拟。通过实验,校核模型参数,并验证模型。结果表明,该模型能较好模拟潜流湿地中有机污染物的去除效果;计算条件下,在不同基质填料的潜流湿地中都会出现滞水区和快速通道,影响水力效率与污染物去除效果;预测了不同填料系统中7种典型选控性有机污染物的去除效果,其处理效率:苯胺苯酚二甲苯甲苯苯硝基苯氯苯,可通过优选填料提高吸附量和延长停留时间来提高选控性有机物的处理效果。 相似文献
70.
Hollie M. Smith Laura Lindenfeld 《Environmental Communication: A Journal of Nature and Culture》2014,8(2):179-196
Research in the area of media coverage on climate change communication represents one of the most prolific areas of inquiry within communication and mass communication studies. This body of literature, which ranges from empirical to critical studies, continues to expand. Much research has focused on representations of climate change causes, effects, and human actions, while some has assessed the impacts of these representations. What is broadly missing from this literature, however, is a discussion of how we might integrate media analysis into transdisciplinary collaborative research aimed at creating solutions to the social, environmental, and economic issues intertwined with climate change. Given the magnitude of problems the society and science are currently grasping with, it behooves us to understand how media studies can contribute most effectively to characterizing and solving problems. We maintain that the move toward integrating media studies into transdisciplinary collaborative research marks an essential transition for environmental communication in general, but climate change communication in particular, given the urgency and magnitude of creating meaningful adaptation and mitigation strategies to address this pressing, complex challenge. Drawing on our work as part of a large transdisciplinary sustainability science team, we provide a case study for understanding what collaborations are key to moving media studies into a transdisciplinary context and the key opportunities and barriers that come along with that move. We argue that media studies must increasingly engage directly in collaboration with other researchers, stakeholders, and communities to serve on-the-ground decision-making and enhance society's ability to take action. 相似文献