共查询到20条相似文献，搜索用时 234 毫秒
1.
2.
层状岩体三维可视化构模与数值模拟的集成研究 总被引：9，自引：0，他引：9
由于数据结构的差异,用于岩土工程三维可视化的网格与用于数值模拟的计算网格之间存在本质差异,如何通过两种网格的共享实现三维地质模型与数值模拟之间的集成是岩土工程建模的重要内容。在对层状岩体三维可视化网格与数值模拟网格的特点进行剖析的基础上,提出了基于松散模式的三维规则格网与FLAC3D基本元素之间的转化方法,从理论上实现了“可视”与“可算”的结合。将其应用于我国某海底隧道的选线研究中,证明了该方法的合理性和有效性。 相似文献
3.
4.
《水文地质工程地质》2000,27(4)
GWMS三维地下水水流和溶质运移模型系统 中国地质科学院水文地质环境地质研究所(保定)是国内专门从事水文地质、工程地质和环境地质勘探评价新方法、新技术研究与开发的科研单位。我所结合科研和水文工程项目,在国外先进软件基础上,开发研制了地下水资源评价系列应用软件。全部软件基于Windows环境,完全可视化操作界面。软件实用高效,适合于各类水源地或区域地下水资源评价和预报。在国内已拥有众多用户,并得到用户一致好评。 GWMS－3D地下水水流和溶质运移模型系统简介 用于二维或三维地下水水流和污染质/地热运移数值模拟和预报。GWMS\|3D模型基于Galerki n有限元方法,系统提供了方便的图形化数据编辑方式和多种结果表达形式,使得模型建立和改进更快捷高效。 ●系统主要特点： ◇自动网格生成,节点减、边界扩缩,局部网格加密 ◇模型以工程文件形式记盘,便于随时改进; ◇参数数据可视化方式输入和编辑;模型可即时改进,三种边界类型任意变动 ◇水流模型能够对复杂边界和多含水层的地下水系统进行模拟预报运移模型和水流模型完全耦合,可考虑延迟、弥散、细菌或放射性衰减等作用过程 ◇模型运行结果直接以彩色平面等值线、流向图或时间系列图等方式显示或打印输出 ◇易于在原模型区域创建子模型,以便地下水系统细化分析研究 ●联系方式 单位：中国地质科学院水文地质环境地质研究所(保定) 地址：河北省保定市七一中路135号邮编：071051 联系人：潘世兵邢卫国 电话：0312－3132642(O),3161729(H),13903223951 E－Mail:span@bd－user.he.cninfo.net 相似文献
5.
6.
《物探化探计算技术》2017,(6)
为满足电磁法二维数值模拟解释对交互建模与可视化网格剖分的需求,利用计算机图形学、人机交互、拓扑关系学等技术,设计了基于测线、测点等信息的二维矢量建模、四边形和三角形网格剖分方法与流程,并开发形成了软件模块。该方法与软件可提供起伏地形下大地电磁、可控源音频大地电磁法二维数值模拟的三角形、四边形网格(下边界随地形变化或平地形)剖分实用化工具。将该方法应用到多种模型试验中,取得了良好的建模与网格剖分效果。 相似文献
7.
8.
运用一种移动粒子半隐式法建立无网格水流数值模型,探讨该模型在结构物水动力特性研究中的可能性。在无网格条件下,粒子间的相互作用通过核子函数来表示,并通过建立物理量光滑模型、梯度模型和二阶导数模型来离散控制方程。流体的不可压缩性是通过引入粒子数密度概念实现的。该方法不受流体变形程度和固边界形状的限制,因而具有特定的适应性。运用该模型模拟了水柱倒塌后有无透空块体两种情况下右端直墙上的压力过程。计算结果表明透空块体可使直墙压力减小42%。 相似文献
9.
10.
11.
For research on granular materials, establishing a method to calculate continuum strain from particle displacements is necessary for understanding the material behaviour at macro-level and developing continuum constitutive models. Existing methods are generally based on constructing a mesh or background grid to calculate strain from particle motions. These methods offer rigorous ways to measure strain for granular materials; however, they suffer from several problems such as mesh distortion and lacking grid-to-particle strain mapping procedure, which hinders their capability of calculating strain accumulation during large deformation processes of granular media. To address this issue, this study proposes a new strain calculation method for discrete element simulations of granular materials. This method describes a particle assembly as an equivalent continuum system of material points, each of which corresponds to a particle centre and represents a continuous region with its initial volume/area presumably equal to the volume/area of Voronoi cells generated in accordance with the particle assembly configuration. Smooth Particle Hydrodynamics (SPH) interpolation functions are then employed to calculate strain for these material points. This SPH-based method does not require any mesh or background grid for computation, leading to advantages in calculating strain accumulation under large deformation. Simulations of granular materials in both uniform and heterogeneous gradations were carried out, and strain results obtained by the proposed method indicate good agreements with analytical and numerical solutions. This demonstrates its potential for strain calculations in discrete element simulations of granular materials involving large deformations and/or large displacements. 相似文献
12.
A comparative study of various commercially available programs in slope stability analysis 总被引：1，自引：0，他引：1
Wael Alkasawneh Abdallah I. Husein Malkawi Jamal Hassan Nusairat Nermeen Albataineh 《Computers and Geotechnics》2008,35(3):428-435
The objective of this paper is to study the effect of different slip surface search techniques on the factors of safety obtained using the limit equilibrium (LE) slope stability methods. This objective is accomplished by comparing results from the finite element method, the linear grid method, the rectangular grid method, and the Monte-Carlo searching techniques using different commercially available programs. The results showed that the LE methods are very efficient methods when coupled with a robust searching technique namely the Monte-Carlo method. In addition, the selected slip surface search technique highly influenced the location of the critical slip surfaces as well as the value of the calculated factors of safety. 相似文献
13.
倾斜层状地层中速度模型对于震源精确定位具有重要意义。基于水平层状地层两点间的快速射线追踪法,分析了应力波在倾斜地层中的传播路径及规律。结合网格搜索法,提出了针对倾斜地层的微震定位算法,并与传统的基于单一速度模型的定位算法进行对比分析;探索性地采用了颗粒流理论构建地层数值模型,通过颗粒间的相互作用模拟应力波传播进行定位算法有效性验证。研究结果表明：（1）对于倾斜地层,基于简化弹性波等速传播规律的定位算法精度较差,单一速度模型不能满足复杂介质的定位要求;（2）采用倾斜分层速度模型并改进应力波传播路径的计算方法能有效提高倾斜地层的震源定位精度,同时分析了地层倾角以及地层数对算法精度的影响,表明定位误差与倾角、地层数成正比;（3）通过减小网格搜索法的网格尺寸可在一定程度上提高定位精度,合理的尺寸大小和搜索策略有助于网格搜索法在实际工程中的应用。建立的倾斜地层震源定位及其验证方法可为进一步研究复杂地层定位监测技术提供重要的理论和技术支撑。 相似文献
14.
Smoothed particle hydrodynamics (SPH) is a meshfree, Lagrangian particle method which has advantages in handling solids with extremely large deformation. Like any other numerical methods, cares must be taken to ensure its desirable accuracy and stability through considering several correction techniques in calculation. The selection of values for parameters in those correction approaches is a key step in SPH simulation, which is always difficult for new beginners to deal well with effectively. This paper examines the common inconsistency and instability problems in SPH method and studies its computational efficiency when applied to hydrodynamics problems with material strength like soil column collapse. We analyzed in detail how the correction techniques mitigate these inconsistency and instability problems. Also, the numerical testing results associate with different values for the parameters used in the correction techniques are provided for better understanding the influence of these parameters and for finding out the desirable values. It is found that (1) the SPH method is easily subjected to an inconsistency problem in the boundary area due to the boundary deficiency, and it can be treated well by adopting “virtual particles” contributing to the particle summations. (2) The numerical oscillation in SPH simulation can be mitigated effectively by artificial viscosity with the suggested parameter values. (3) The tension cracking treatment, artificial viscosity and artificial stress work well in removing the tensile instability problem in SPH method. In addition, the nearest neighboring particle searching (NNPS) algorithm, spacing ratio, smoothing length and time step influence the efficiency and accuracy of SPH method significantly. It is shown that SPH method with suggested parameters values can produce a very good result compared with the experimental result. 相似文献
15.
Multiscale mixed/mimetic methods on corner-point grids 总被引：1，自引：0，他引：1
Multiscale simulation is a promising approach to facilitate direct simulation of large and complex grid models for highly
heterogeneous petroleum reservoirs. Unlike traditional simulation, approaches based on upscaling/downscaling, multiscale methods
seek to solve the full flow problem by incorporating subscale heterogeneities into local discrete approximation spaces. We
consider a multiscale formulation based on a hierarchical grid approach, where basis functions with subgrid resolution are
computed numerically to correctly and accurately account for subscale variations from an underlying (fine-scale) geomodel
when solving the global flow equations on a coarse grid. By using multiscale basis functions to discretise the global flow
equations on a (moderately sized) coarse grid, one can retain the efficiency of an upscaling method and, at the same time,
produce detailed and conservative velocity fields on the underlying fine grid. For pressure equations, the multiscale mixed
finite-element method (MsMFEM) has been shown to be a particularly versatile approach. In this paper, we extend the method
to corner-point grids, which is the industry standard for modelling complex reservoir geology. To implement MsMFEM, one needs
a discretisation method for solving local flow problems on the underlying fine grids. In principle, any stable and conservative
method can be used. Here, we use a mimetic discretisation, which is a generalisation of mixed finite elements that gives a
discrete inner product, allows for polyhedral elements, and can (easily) be extended to curved grid faces. The coarse grid
can, in principle, be any partition of the subgrid, where each coarse block is a connected collection of subgrid cells. However,
we argue that, when generating coarse grids, one should follow certain simple guidelines to achieve improved accuracy. We
discuss partitioning in both index space and physical space and suggest simple processing techniques. The versatility and
accuracy of the new multiscale mixed methodology is demonstrated on two corner-point models: a small Y-shaped sector model
and a complex model of a layered sedimentary bed. A variety of coarse grids, both violating and obeying the above mentioned
guidelines, are employed. The MsMFEM solutions are compared with a reference solution obtained by direct simulation on the
subgrid. 相似文献
16.
G. Bernard-Michel C. Le Potier A. Beccantini S. Gounand M. Chraibi 《Computational Geosciences》2004,8(2):187-201
We present here results for the Andra Couplex 1 test case, obtained with the code Cast3m. This code is developped at the CEA (Commissariat l'nergie atomique) and is used mainly to solve problems of solid mechanics, fluid mechanics and heat transfers. Different types of discretization are available, among them finite element, finite volume and mixed hybrid finite element method. Cast3m is also a componant of the platteform Alliances (co-developped by Andra, CEA), which will be used by Andra for the safety calculation of an underground waste disposal in year 2004. We solve the Darcy equation for the water flow and a convection–diffusion transport equation for the Iodine 129 which escapes from a repository cave into the water. The water flow is calculated with a MHFE discretization. It is shown that this method provides sharp results even on relatively coarse grids. The convection–diffusion transport equation is discretized with FE (Finite Element), MHFE (Mixed Hybrid Finite Element) and FV (Finite Volume) methods. In our comparison, we point out the differences of these methods in term of accuracy, respect of the maximum principle and calculations cost. Neither the finite element nor the mixed hybrid finite element approach respects the maximum principle. This results in the presence of negative concentrations near the repository cave, whereas FV calculations respect the monotonicity. We show that mass lumping techniques suppress this problem but with strong restrictions on the grid. FE and MHFE approaches are more accurate than FV for the diffusion equation, but the overall results are equivalent since the advective terms are dominant in the far field and are discretized with centered schemes. We conclude by studying the influence of the grid: a very fine grid near the repository solves almost all the problems of monotonicity, without employing mass lumping techniques. We also observed a very important increase of the accuracy on a structured grid made up of rectangles. 相似文献
17.
Trond Mannseth 《Computational Geosciences》2007,11(1):59-72
We consider discretization on quadrilateral grids of an elliptic operator occurring, for example, in the pressure equation
for porous-media flow. In a realistic setting – with non-orthogonal grid, and anisotropic, heterogeneous permeability – special
discretization techniques are required. Mixed finite element (MFE) and multipoint flux approximation (MPFA) are two methods
that can handle such situations. Previously, a framework for analytical comparison of MFE and MPFA in special cases has been
suggested. A comparison of MFE and MPFA-O (one of two main variants of MPFA) for isotropic, homogeneous permeability on a
uniformly distorted grid was also performed. In the current paper, we utilize the suggested framework in a slightly different
manner to analyze and compare MFE, MPFA-O and MPFA-U (the second main variant of MPFA). We reconsider the case previously
analyzed. We also consider the case of generally anisotropic, homogeneous permeability on an orthogonal grid. 相似文献
18.
The observation that the results of line and point counting analyses of the particle size distribution of the same sand are different leads to the conclusion that these results are biased by the sampling technique1 . The influence of the currently used sampling techniques on the numerical results of a particle size analysis is discussed. Evidence is presented to show that the use of line and point counting methods in granulometric analysis leads to results in which the influence of the sampling method is so strong that the practical value of these techniques is doubtful. It is therefore considered advisable to discontinue line and point counting techniques in granulometric analysis in favour of ribbon sampling methods. 相似文献
19.
20.
C. R. Dietrich 《Mathematical Geology》1993,25(4):439-451
The generation over two-dimensional grids of normally distributed random fields conditioned on available data is often required in reservoir modeling and mining investigations. Such fields can be obtained from application of turning band or spectral methods. However, both methods have limitations. First, they are only asymptotically exact in that the ensemble of realizations has the correlation structure required only if enough harmonics are used in the spectral method, or enough lines are generated in the turning bands approach. Moreover, the spectral method requires fine tuning of process parameters. As for the turning bands method, it is essentially restricted to processes with stationary and radially symmetric correlation functions. Another approach, which has the advantage of being general and exact, is to use a Cholesky factorization of the covariance matrix representing grid points correlation. For fields of large size, however, the Cholesky factorization can be computationally prohibitive. In this paper, we show that if the data are stationary and generated over a grid with regular mesh, the structure of the data covariance matrix can be exploited to significantly reduce the overall computational burden of conditional simulations based on matrix factorization techniques. A feature of this approach is its computational simplicity and suitability to parallel implementation. 相似文献