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1.
Emil M. Constantinescu Adrian Sandu Gregory R. Carmichael 《Computational Geosciences》2008,12(2):133-151
We discuss an adaptive resolution system for modeling regional air pollution based on the chemical transport model STEM. The
grid adaptivity is implemented using the generic adaptive mesh refinement tool Paramesh, which enables the grid management
operations while harnessing the power of parallel computers. The computational algorithm is based on a decomposition of the
domain, with the solution in different subdomains being computed with different spatial resolutions. Various refinement criteria
that adaptively control the fine grid placement are analyzed to maximize the solution accuracy while maintaining an acceptable
computational cost. Numerical experiments in a large-scale parallel setting (~0.5 billion variables) confirm that adaptive
resolution, based on a well-chosen refinement criterion, leads to the decrease in spatial error with an acceptable increase
in computational time. Fully dynamic grid adaptivity for air quality models is relatively new. We extend previous work on
chemical and transport modeling by using dynamically adaptive grid resolution. Advantages and shortcomings of the present
approach are also discussed. 相似文献
2.
George Shu Heng Pau John B. Bell Ann S. Almgren Kirsten M. Fagnan Michael J. Lijewski 《Computational Geosciences》2012,16(3):577-592
We describe a second-order accurate sequential algorithm for solving two-phase multicomponent flow in porous media. The algorithm
incorporates an unsplit second-order Godunov scheme that provides accurate resolution of sharp fronts. The method is implemented
within a block structured adaptive mesh refinement (AMR) framework that allows grids to dynamically adapt to features of the
flow and enables efficient parallelization of the algorithm. We demonstrate the second-order convergence rate of the algorithm
and the accuracy of the AMR solutions compared to uniform fine-grid solutions. The algorithm is then used to simulate the
leakage of gas from a Liquified Petroleum Gas (LPG) storage cavern, demonstrating its capability to capture complex behavior
of the resulting flow. We further examine differences resulting from using different relative permeability functions. 相似文献
3.
在对国内外水问题进行科学识别的基础上,分析了水循环的"自然-人工"二元演变模式,明晰了水循环及伴生水化学、水生态和水沙过程的相互关系,初步阐述了现代水文水资源学科体系的构成。在对国际水文水资源研究发展趋势及热点和前沿问题进行阐释的基础上,结合中国水文水资源研究现状及水问题解决的实践需求,论述了中国水文水资源研究的学科体系的构成,并分析其重大研究方向。在变化环境和高强度人类活动影响下,水循环在驱动力、结构及参数等方面已呈现出显著"自然-人工"二元特征。现代水文水资源研究正由传统"还原细化"研究向综合交叉方向发展,并由传统基于单个水文环节的研究过渡到基于二元水循环过程的研究上来,原型观测与数学模拟的结合已成为其关键研究手段。中国水文水资源研究需要进一步强化水循环及伴生过程演变机理识别与定量模拟方面的基础研究,完善水资源评价、配置、调度、水权分配、水价定价理论和技术等方面的应用基础研究,服务于节水型社会建设、水环境保护与水生态修复、水资源综合管理、防灾减灾与应急管理、民生水利及现代水利建设与管理等实践需求。 相似文献
4.
基于粗细网格的有限元并行分析方法 总被引：2，自引：0，他引：2
并行计算己成为求解大规模岩土工程问题的一种强大趋势。探讨了粗细网格与预处理共轭梯度法结合的并行有限元算法。从多重网格刚度矩阵推得有效的预处理子。该算法在工作站机群上实现。用地基处理时土体强夯的数值模拟分析进行了数值测试,对其并行性能进行了详细分析。计算结果表明：该算法具有良好的并行加速比和效率,是一种有效的并行算法。 相似文献
5.
Coupled hydromechanical‐fracture simulations of nonplanar three‐dimensional hydraulic fracture propagation 
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下载免费PDF全文 This paper presents an algorithm and a fully coupled hydromechanical‐fracture formulation for the simulation of three‐dimensional nonplanar hydraulic fracture propagation. The propagation algorithm automatically estimates the magnitude of time steps such that a regularized form of Irwin's criterion is satisfied along the predicted 3‐D fracture front at every fracture propagation step. A generalized finite element method is used for the discretization of elasticity equations governing the deformation of the rock, and a finite element method is adopted for the solution of the fluid flow equation on the basis of Poiseuille's cubic law. Adaptive mesh refinement is used for discretization error control, leading to significantly fewer degrees of freedom than available nonadaptive methods. An efficient computational scheme to handle nonlinear time‐dependent problems with adaptive mesh refinement is presented. Explicit fracture surface representations are used to avoid mapping of 3‐D solutions between generalized finite element method meshes. Examples demonstrating the accuracy, robustness, and computational efficiency of the proposed formulation, regularized Irwin's criterion, and propagation algorithm are presented. 相似文献
6.
Numerical challenges occur in the simulation of groundwater flow problems because of complex boundary conditions, varying material properties, presence of sources or sinks in the flow domain, or a combination of these. In this paper, we apply adaptive isogeometric finite element analysis using locally refined (LR) B‐splines to address these types of problems. The fundamentals behind isogeometric analysis and LR B‐splines are briefly presented. Galerkin's method is applied to the standard weak formulation of the governing equation to derive the linear system of equations. A posteriori error estimates are calculated to identify which B‐splines should be locally refined. The error estimates are calculated based on recovery of the L2‐projected solution. The adaptive analysis method is first illustrated by performing simulation of benchmark problems with analytical solutions. Numerical applications to two‐dimensional groundwater flow problems are then presented. The problems studied are flow around an impervious corner, flow around a cutoff wall, and flow in a heterogeneous medium. The convergence rates obtained with adaptive analysis using local refinement were, in general, observed to be of optimal order in contrast to simulations with uniform refinement. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
7.
MODIS是新一代遥感技术,其遥测数据与其他单独的遥感平台(如NOAA和Land Sat)所获得的数据相比,具有免费、较高时间分辨率(0.5d)、空间分辨率(250m)和光谱分辨率(波谱范围0.4～14μm,36个光谱通道)等优势和特点.详细介绍了国内外的研究现状,着重对MODIS在洪水过程和洪灾范围实时动态监测、冰川和积雪、降水、植被、土壤水分、蒸发、水文模型、水质等方面的应用和研究进展进行了评述,指出MODIS在水文水资源中具有广阔的应用前景. 相似文献
8.
Yuyu Zhou Yeqiao Wang Arthur J. Gold Peter V. August Thomas B. Boving 《GeoJournal》2014,79(2):155-166
In this study, we investigated the relationship between watershed characteristics and hydrology using high spatial resolution impervious surface area (ISA), hydrologic simulations and spatial regression. We selected 20 watersheds at HUC 12 level with different degrees of urbanization and performed hydrologic simulation using a distributed object-oriented rainfall and runoff simulation model. We extracted the discharge per area and ratio of runoff to base flow from simulation results and used them as indicators of hydrology pattern. We derived percentage of ISA, distance from ISA to streams, and stream density as the watershed characteristics to evaluate the relationship with hydrology pattern in watersheds using ordinary least square, spatial error and spatial lag regression models. The comparison indicates that spatial lag regression model can achieve better performance for the evaluation of relationship between ratio of runoff to base flow and watershed characteristics, and that three models provide similar performance for the evaluation of relationship between discharge per area and watershed characteristics. The results from regression analyses demonstrate that ISA plays an important role in watershed hydrology. Ignorance of spatial dependence in analyses will likely cause inaccurate evaluation for relationship between ISA and watershed hydrology. The hydrologic model, regression methods and relationships between watershed characteristics and hydrology pattern provide important tools and information for decision makers to evaluate the effect of different scenarios in land management. 相似文献
9.
大数据科学研究范式是大数据时代的必然结果。在大数据时代,地质学研究正面临着前所未有的挑战与机遇,亟需地质大数据分析的基础支撑。本文介绍若干种有价值的地质大数据分析工具及其应用。知识图谱以其强大的语义处理能力和开放组织能力,为大数据时代信息的知识化组织和智能应用提供了有效工具。它旨在描述真实世界中存在的各种实体或概念及其关系,构成一张巨大的语义网络图,以节点表示实体或概念,边则由属性或关系构成。机器学习与卷积神经网络模型仍然是当前地质大数据研究的热点。演化算法借鉴了自然界中生物进化与自适应过程的思想,是一种基于种群的元启发式最优化算法。它具有无需先验知识、能在全局范围内进行隐并行搜索的优点,可以用来精确地获取大数据中隐含的演化趋势与时空特征。图形社区发现技术将网络划分为若干个内部节点相似社区,为分析和理解网络提供有力的技术支持。随着空间分辨率、时间分辨率和辐射分辨率不断提高,遥感技术已广泛成为地质数据获得的主要技术手段。遥感大数据的数据存取和智能处理是最重要的发展方向。这些地质大数据分析方法已有成功的应用案例,并将广泛用于各种地质研究,如城市土壤污染智能监测、模拟、管控与预警研究,得益于地质大数据研究支撑系统的恰当选择以及地质大数据技术的强力支持,建立了可解释的多源多层城市土壤污染知识图谱,源于多源异构大数据有效融合的主要障碍正在去除。 相似文献
10.
Natural evaporite dissolution in the subsurface can lead to cavities having critical dimensions in the sense of mechanical stability. Geomechanical effects may be significant for people and infrastructures because the underground dissolution may lead to subsidence or collapse (sinkholes). The knowledge of the cavity evolution in space and time is thus crucial in many cases. In this paper, we describe the use of a local nonequilibrium diffuse interface model for solving dissolution problems involving multimoving interfaces within three phases, that is, solid–liquid–gas as found in superficial aquifers and karsts. This paper generalizes developments achieved in the fluid–solid case, that is, the saturated case [1]. On one hand, a local nonequilibrium dissolution porous medium theory allows to describe the solid–liquid interface as a diffuse layer characterized by the evolution of a phase indicator (e.g., porosity). On the other hand, the liquid–gas interface evolution is computed using a classical porous medium two‐phase flow model involving a phase saturation, that is, generalized Darcy's laws. Such a diffuse interface model formulation is suitable for the implementation of a finite element or finite volume numerical model on a fixed grid without an explicit treatment of the interface movement. A numerical model has been implemented using a finite volume formulation with adaptive meshing (e.g., adaptive mesh refinement), which improves significantly the computational efficiency and accuracy because fine gridding may be attached to the dissolution front. Finally, some examples of three‐phase dissolution problems including density effects are also provided to illustrate the interest of the proposed theoretical and numerical framework. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Abid Ali A. V. Lyamin Jinsong Huang J. H. Li M. J. Cassidy S. W. Sloan 《Acta Geotechnica》2017,12(4):937-948
For deterministic scenarios, adaptive finite element limit analysis has been successfully employed to achieve tight bounds on the ultimate load of a geotechnical structure in a much more efficient manner than a dense uniform mesh. However, no probabilistic studies have so far considered finite element limit analysis with adaptive remeshing. Therefore, this research explores the benefits of combining adaptive mesh refinement with finite element limit analysis for probabilistic applications. The outcomes indicate that in order to achieve tight bounds on probabilistic results (such as the probability of failure), the ultimate load in each individual simulation (e.g. factor of safety or bearing capacity) has to be estimated with a very high level of accuracy and this can be achieved more economically using adaptive mesh refinement. The benefits, assessed here for undrained conditions, are expected to be much more pronounced in the case of frictional soils and complex geometries. 相似文献
14.
Yifeng Cui Reagan Moore Kim Olsen Amit Chourasia Philip Maechling Bernard Minster Steven Day Yuanfang Hu Jing Zhu Thomas Jordan 《Acta Geotechnica》2009,4(2):79-93
Earthquakes are among the most complex terrestrial phenomena, and modeling of earthquake dynamics is one of the most challenging
computational problems in science. Computational capabilities have advanced to a state where we can perform wavefield simulations
for realistic three-dimensional earth models, and gain more insights into the earthquakes that threaten California and many
areas of the world. The Southern California Earthquake Center initiated a major earthquake research program called TeraShake
to perform physics-based numerical simulations of earthquake processes for large geographical regions, at high resolution,
and for high frequencies. For a large scale simulation such as TeraShake, optimization problems tend to emerge that are not
significant in smaller scale simulations. This involves both large parallel computation and also massive data management and
visualization coordination. In this paper, we describe how we performed single-processor optimization of the TeraShake AWM
application, optimization of the I/O handling, and optimization of initialization. We also look at the challenges presented
by run-time data archive management and visualization. The improvements made to the TeraShake AWM code enabled execution on
the 40k IBM Blue Gene processors and have created a community code that can be used by seismologists to perform petascale
earthquake simulations. 相似文献
15.
条件模拟是一种计算非常耗时的高精度三维插值算法。针对串行条件模拟算法计算时间过长的问题,提出基于GPU的并行条件模拟算法,并进行储量估算。对条件模拟算法进行并行分析,利用GPU的高度并行性,构建CUDA通用计算开发环境,实现串行条件模拟算法到并行条件模拟算法的转换,使条件模拟算法的时间复杂度从O(n)降至O(logn)。并对西藏甲玛铜矿进行了储量估算。实验结果表明,在安装普通NVIDIA显卡的计算机以及估算精度不下降的情况下,GPU并行条件模拟的计算效率比CPU串行条件模拟的计算效率提高了60倍以上。 相似文献
16.
A GIS-based decision support system, which incorporates local topographic and rainfall effects on debris flow vulnerability
is developed. Rainfall at a scale compatible with the digital elevation model resolution is obtained using a neural network
with a wind-induced topographic effect and rainfall derived from satellite rain estimates and an adaptive inverse distance
weight method (WTNN). The technique is tested using data collected during the passage of typhoon Tori-Ji on July 2001 over
central Taiwan. Numerous debris flows triggered by the typhoon were used as control for the study. Our results show that the
WTNN technique outperforms other interpolation techniques including adaptive inversed distance weight (AIDW), simple kriging
(SK), co-kriging, and multiple linear regression using gauge, and topographic parameters. Multiple remotely-sensed, fuzzy-based
debris-flow susceptibility parameters are used to describe the characteristics of watersheds. Non-linear, multi-variant regressions
using the WTNN derived rainfall and topography factors are derived using self-organizing maps (SOM) for the debris flow vulnerability
assessment. An index of vulnerability representing the degrees of hazard is implemented in a GIS-based decision support system
by which a decision maker can assess debris flow vulnerability. 相似文献
18.
遥感图像处理常见的困难有数据量巨大、噪声信息多，高度非线性及其导致的难以用解析或表述处理模型等。人工神经网络（artificial neural network,ANN)是由大量简单神经元广泛相互联接而成的非线性映射或自适应动力系统，可以解决上述问题，使用ANN进行遥感图像处理在遥感图像复原，变换和分类中有如下应用：（1）使用ANN和必要辅助数据从TM图像中提取地下火热辐射数据；（2）构造ANN非线性映射，利用TM1－5，7图像提高TM6图像空间分辨率；（3）模糊神经网络（FNN）遥感图像分类。 相似文献
19.
Ádám Leelőssy Ferenc Molnár Jr. Ferenc Izsák Ágnes Havasi István Lagzi Róbert Mészáros 《Central European Journal of Geosciences》2014,6(3):257-278
Modeling of dispersion of air pollutants in the atmosphere is one of the most important and challenging scientific problems. There are several natural and anthropogenic events where passive or chemically active compounds are emitted into the atmosphere. The effect of these chemical species can have serious impacts on our environment and human health. Modeling the dispersion of air pollutants can predict this effect. Therefore, development of various model strategies is a key element for the governmental and scientific communities. We provide here a brief review on the mathematical modeling of the dispersion of air pollutants in the atmosphere. We discuss the advantages and drawbacks of several model tools and strategies, namely Gaussian, Lagrangian, Eulerian and CFD models. We especially focus on several recent advances in this multidisciplinary research field, like parallel computing using graphical processing units, or adaptive mesh refinement. 相似文献
20.
Multiple-point statistics (MPS) provides a flexible grid-based approach for simulating complex geologic patterns that contain high-order statistical information represented by a conceptual prior geologic model known as a training image (TI). While MPS is quite powerful for describing complex geologic facies connectivity, conditioning the simulation results on flow measurements that have a nonlinear and complex relation with the facies distribution is quite challenging. Here, an adaptive flow-conditioning method is proposed that uses a flow-data feedback mechanism to simulate facies models from a prior TI. The adaptive conditioning is implemented as a stochastic optimization algorithm that involves an initial exploration stage to find the promising regions of the search space, followed by a more focused search of the identified regions in the second stage. To guide the search strategy, a facies probability map that summarizes the common features of the accepted models in previous iterations is constructed to provide conditioning information about facies occurrence in each grid block. The constructed facies probability map is then incorporated as soft data into the single normal equation simulation (snesim) algorithm to generate a new candidate solution for the next iteration. As the optimization iterations progress, the initial facies probability map is gradually updated using the most recently accepted iterate. This conditioning process can be interpreted as a stochastic optimization algorithm with memory where the new models are proposed based on the history of the successful past iterations. The application of this adaptive conditioning approach is extended to the case where multiple training images are proposed as alternative geologic scenarios. The advantages and limitations of the proposed adaptive conditioning scheme are discussed and numerical experiments from fluvial channel formations are used to compare its performance with non-adaptive conditioning techniques. 相似文献