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991.
垃圾渗滤液污染地下环境介质岩性对pH缓冲能力的影响 总被引:1,自引:1,他引:0
通过模拟实验研究垃圾渗滤液污染地下环境介质岩性对pH缓冲能力变化的影响。亚黏土和砂土的pH缓冲容量的本底值分别为440.20和324.93mmol/(kg·pH),其中阳离子交换缓冲、碳酸钙缓冲、硅酸盐缓冲和次级缓冲的本底值分别为206.18、88.43、75.79和69.80mmol/(kg·pH),149.31、86.53、47.33和41.77mmol/(kg·pH)。污染的亚黏土和砂土的交换性阳离子(CEC)和交换性盐基离子(BEC)均小于本底值;盐基饱和度随离污染源距离的增加呈先升高后降低的变化趋势。 相似文献
992.
最小二乘配点无网格法是一种新型高效的无网格法。该方法除节点外又在研究域内引入辅助点,近似函数仍然只通过节点构造,微分方程在所有节点和辅助点上满足。本文将最小二乘配点无网格法应用于非均质多孔介质中的二维地下水稳定流问题,推导了计算格式、编制了相应的计算程序。算例结果表明,最小二乘配点无网格法算法简单,有较高的精度且节省计算量。 相似文献
993.
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995.
地震波在粘弹性介质中传播的一个基本特征是能量的衰减及地震波的瞬时波形变化。从广义上说,衰减可分为两类:一类是与地震波传播特性有关的衰减|另一类是反映介质内在属性的地层本征衰减,地层的本征衰减通常用品质因子来度量。反演品质因子的方法有多种,常用的是谱模拟频谱比法。笔者的主要目的是通过模型试算来分析评价该方法在反演品质因子时对干涉和噪声的稳定性,得出有益的结论,用于指导反演计算。 相似文献
996.
One of the driving forces in porous media flow is the capillary pressure. In standard models, it is given depending on the
saturation. However, recent experiments have shown disagreement between measurements and numerical solutions using such simple
models. Hence, we consider in this paper two extensions to standard capillary pressure relationships. Firstly, to correct
the nonphysical behavior, we use a recently established saturation-dependent retardation term. Secondly, in the case of heterogeneous
porous media, we apply a model with a capillary threshold pressure that controls the penetration process. Mathematically,
we rewrite this model as inequality constraint at the interfaces, which allows discontinuities in the saturation and pressure.
For the standard model, often finite-volume schemes resulting in a nonlinear system for the saturation are applied. To handle
the enhanced model at the interfaces correctly, we apply a mortar discretization method on nonmatching meshes. Introducing
the flux as a new variable allows us to solve the inequality constraint efficiently. This method can be applied to both the
standard and the enhanced capillary model. As nonlinear solver, we use an active set strategy combined with a Newton method.
Several numerical examples demonstrate the efficiency and flexibility of the new algorithm in 2D and 3D and show the influence
of the retardation term.
This work was supported in part by IRTG NUPUS. 相似文献
997.
Guillermo A. Narsilio Olivier Buzzi Stephen Fityus Tae Sup Yun David W. Smith 《Computers and Geotechnics》2009,36(7):1200-1206
The accurate estimation of hydraulic conductivity is important for many geotechnical engineering applications, as the presence of fluids affects all aspects of soil behaviour, including its strength. Darcy’s law is the key experimental (or phenomenological) equation employed to model ground water flow. Yet, this phenomenological equation can be linked to a more fundamental microscale model of flow through the pore spaces of the porous material. This paper provides an experimental verification of the relationships between Darcy’s law (macroscale) and the Navier–Stokes equations (microscale) for actual complex pore geometries of a granular material. The pore geometries are experimentally obtained through state-of-the-art X-ray computer assisted micro-tomography. From the numerical modelling of the microscale flow based on actual pore geometries, it is possible to quantify and visualize the development of pore-scale fluid preferential flow-paths through the porous material, and to assess the importance of pore connectivity in soil transport properties. 相似文献
998.
Simon K. Alexander Paul Fieguth Marios A. Ioannidis Edward R. Vrscay 《Mathematical Geosciences》2009,41(4):357-378
This paper introduces a hierarchical annealing algorithm which addresses the very large computational costs associated with
simulated annealing for the synthesis of binary images. In real-world examples, the large configuration space of such models
has led to the disappointing performance of annealing approaches. Our method essentially approaches different natural scales
in the image separately and in a hierarchical manner. We demonstrate orders-of-magnitude improvement compared to existing
results, and discuss the inherent computational difficulties encountered with these types of approaches. 相似文献
999.
A discrete element method is applied to a three‐dimensional analysis related to sediment entrainment on a micro‐scale. Sediment entrainment is the process by which a fluid medium accelerates particles from rest and advects them upward until they are either transported as bedload or suspended by the flow. Modelling of the entrainment process is a critically important aspect for studies of erosion, pollutant resuspension and transport, and formation of bedforms in environmental flows. Previous discrete element method studies of sediment entrainment have assumed the flow within the particle bed to be negligible and have only allowed for the motion of the topmost particles. At the same time, micro‐scale experimental studies indicate that there is a small slip of the fluid flow at the top of the bed, indicating the presence of non‐vanishing fluid velocity within the topmost bed layers. The current study demonstrates that the onset of particle incipient motion, which immediately precedes particle entrainment, is highly sensitive to this small fluid flow within the topmost bed layers. Using an exponential decay profile for the inner‐bed fluid flow, the discrete element method calculations are repeated with different fluid penetration depths within the bed for several small particle Reynolds numbers. For cases with slip velocity corresponding to that observed in previous experiments with natural sediment, the predicted particle velocity is found to be a few percent of the fluid velocity at the top of the viscous wall layer, which is a reasonable range of velocities for observation of incipient particle motion. This method for prescribing the fluid flow within the particle bed allows for the current discrete element method to be extended in future studies to the analysis of sediment entrainment under the influence of events such as turbulent bursting. Additionally, predictions for the slip velocities and fluid flow profile within the bed suggest the need for further experimental studies to provide the data necessary for additional improvement of the discrete element method models. 相似文献
1000.
与图像内容相关的色域映射算法研究 总被引:2,自引:0,他引:2
通过对经典色域映射算法的调查分析,总结归纳了映射执行中影响图像质量的各个相关因素,在分析其影响权重的基础上建立了一个最佳的映射模型,设计实现了一个与图像内容相关的色域映射算法。测试实验验证,新算法优于ICC推荐的HPMINDE和SGCK算法,确保转换图像的视觉效果最佳。 相似文献