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31.
本文对边界元方法中的各类积分根据其奇异性作分类,并对主值积分的收敛条件、变量替换等进行了讨论,又给出了变替换附加项显式。文中提供的主值积分配项消奇术在边界元方法中是有普遍意义的。 相似文献
32.
CAD软件在工程地质三维建模中的应用 总被引:3,自引:0,他引:3
如何快速、准确地建立地质体的三维模型一直是众多岩土工程数值模拟工作者所面临的难题。虽然三维地学模拟软件具有很好的三维地质建模能力,但是由于数据结构的差异,采用他们现行三维地学模拟软件建立的地质模型难以导入数值模拟分析软件中,以为相应工程问题的数值模拟服务。目前,随着各种CAD、CAM软件行业的的飞速发展,涌现出了许多优秀的三维建模软件,而且这些软件大都与现行数值分析软件有着良好的数据接口功能。据此,本文提出了采用现行CAD软件来建立工程地质体的三维模型,使得建立的模型达到既"可视"又"可算"的目的。将其应用于云南某高速公路边坡的三维建模中,证明了该法具有方便、快捷和合理等优点。 相似文献
33.
地圈中广泛发育的动力学过程属于多元关联过程,它们是在岩土圈与水圈、大气圈、生物圈相互作用中进行的。它们的活动可以概括为热力学、流体力学、固体力学、化学和生物学等基本物质运动的作用及系统的演化。由于它们之间有着互动影响和制约,以及由此引发的能量的转换和参数的变异,因而密切相关。本文建议确立THMCB多元关联过程的概念,开展多元关联过程的研究和分析,以期对地圈动力学过程进行系统有效的综合评价和预测。 相似文献
34.
In this article, both thermal buckling and post-buckling of pinned–fixed beams resting on an elastic foundation are investigated. Based on the accurate geometrically non-linear theory for Euler–Bernoulli beams, considering both linear and non-linear elastic foundation effects, governing equations for large static deformations of the beam subjected to uniform temperature rise are derived. Due to the large deformation of the beam, the constraint forces of elastic foundation in both longitudinal and transverse directions are taken into account. The boundary value problem for the non-linear ordinary differential equations is solved effectively by using the shooting method. Characteristic curves of critical buckling temperature versus elastic foundation stiffness parameter corresponding to the first, the second, and the third buckling mode shapes are plotted. From the numerical results it can be found that the buckling load-elastic foundation stiffness curves have no intersection when the value of linear foundation stiffness parameter is less than 3000, which is different from the behaviors of symmetrically supported (pinned–pinned and fixed–fixed) beams. As we expect that the non-linear foundation stiffness parameter has no sharp influence on the critical buckling temperature and it has a slight effect on the post-buckling temperature compared with the linear one. 相似文献
35.
R. Garg C. Narayanan D. Lakehal S. Subramaniam 《International Journal of Multiphase Flow》2007,33(12):1337-1364
The Lagrangian–Eulerian (LE) approach is used in many computational methods to simulate two-way coupled dispersed two-phase flows. These include averaged equation solvers, as well as direct numerical simulations (DNS) and large-eddy simulations (LES) that approximate the dispersed-phase particles (or droplets or bubbles) as point sources. Accurate calculation of the interphase momentum transfer term in LE simulations is crucial for predicting qualitatively correct physical behavior, as well as for quantitative comparison with experiments. Numerical error in the interphase momentum transfer calculation arises from both forward interpolation/approximation of fluid velocity at grid nodes to particle locations, and from backward estimation of the interphase momentum transfer term at particle locations to grid nodes. A novel test that admits an analytical form for the interphase momentum transfer term is devised to test the accuracy of the following numerical schemes: (1) fourth-order Lagrange Polynomial Interpolation (LPI-4), (3) Piecewise Cubic Approximation (PCA), (3) second-order Lagrange Polynomial Interpolation (LPI-2) which is basically linear interpolation, and (4) a Two-Stage Estimation algorithm (TSE). A number of tests are performed to systematically characterize the effects of varying the particle velocity variance, the distribution of particle positions, and fluid velocity field spectrum on estimation of the mean interphase momentum transfer term. Numerical error resulting from backward estimation is decomposed into statistical and deterministic (bias and discretization) components, and their convergence with number of particles and grid resolution is characterized. It is found that when the interphase momentum transfer is computed using values for these numerical parameters typically encountered in the literature, it can incur errors as high as 80% for the LPI-4 scheme, whereas TSE incurs a maximum error of 20%. The tests reveal that using multiple independent simulations and higher number of particles per cell are required for accurate estimation using current algorithms. The study motivates further testing of LE numerical methods, and the development of better algorithms for computing interphase transfer terms. 相似文献
36.
H. W. Broer I. Hoveijn M. van Noort C. Simó G. Vegter 《Journal of Dynamics and Differential Equations》2004,16(4):897-947
This paper is concerned with the global coherent (i.e., non-chaotic) dynamics of the parametrically forced pendulum. The system is studied in a === degree of freedom Hamiltonian setting with two parameters, where a spatio-temporal symmetry is taken into account. Our explorations are restricted to large regions of coherent dynamics in phase space and parameter plane. At any given parameter point we restrict to a bounded subset of phase space, using KAM theory to exclude an infinitely large region with rather trivial dynamics. In the absence of forcing the system is integrable. Analytical and numerical methods are used to study the dynamics in a parameter region away from integrability, where the analytic results of a perturbation analysis of the nearly integrable case are used as a starting point. We organize the dynamics by dividing the parameter plane in fundamental domains, guided by the linearized system at the upper and lower equilibria. Away from integrability some features of the nearly integrable coherent dynamics persist, while new bifurcations arise. On the other hand, the chaotic region increases.2000 Mathematical Subject Classification: 37J20, 37J40, 37M20, 70H08.Dedicated to Professor Shui-Nee Chow on the occasion of his 60th birthday. 相似文献
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39.
Gérard L. Vignoles Pierre Charrier Christophe Preux Bruno Dubroca 《Transport in Porous Media》2008,75(3):295-317
Viscous flow, effusion, and thermal transpiration are the main gas transport modalities for a rarefied gas in a macro-porous
medium. They have been well quantified only in the case of simple geometries. This paper presents a numerical method based
on the homogenization of kinetic equations producing effective transport properties (permeability, Knudsen diffusivity, thermal
transpiration ratio) in any porous medium sample, as described, e.g. by a digitized 3D image. The homogenization procedure—neglecting
the effect of gas density gradients on heat transfer through the solid—leads to closure problems in for the obtention of effective properties; they are then simplified using a Galerkin method based on a 21-element basis set.
The kinetic equations are then discretized in space with a finite- volume scheme. The method is validated against experimental data in the case of a closed test tube.
It shows to be coherent with past approaches of thermal transpiration. Then, it is applied to several 3D images of increasing
complexity. Another validation is brought by comparison with other distinct numerical approaches for the evaluation of the
Darcian permeability tensor and of the Knudsen diffusion tensor. Results show that thermal transpiration has to be described
by an effective transport tensor which is distinct from the other tensors. 相似文献
40.
本文采用泰勒级数法分析横观各向同性球壳轴对称弯曲问题。将位移沿厚度方向展开成泰勒级数,利用三维弹性方程求得级数中的各阶导数。对于边值问题,用特征函数法满足球面齐次边界条件,并用最小二乘配点法满足端部条件。 相似文献