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981.
含气介质临界点、流体和骨架弹性参数的线性数值计算方法(英文) 总被引:5,自引:0,他引:5
临界孔隙度及其孔隙介质的研究均为测试分析的实验方法,如何运用数值计算方法求取孔隙流体介质临界点、流体和骨架的弹性参数是备受关注的课题。本文提出了求取临界点、流体和骨架弹性参数的数值计算公式及方法,并结合含气样品测试数据实现了这种数值计算。首先,基于孔隙度≯为白变量,而密度ρ,密度与横波速度平方的乘积ρVs^2和密度与纵波速度平方的乘积ρVp^2均为函数的三个线性方程,从每个线性方程中的两个系数的有机组合得到求取有关弹性参的线性数值计算公式。然后,详细阐述了数值计算的步骤和方法以及需要注意的问题,把室内含气砂岩数的线性数值计算公式。然后,详细阐述了数值计算的步骤和方法以及需要注意的问题,把室内含气砂岩样品测试的整体介质密度、纵波速度和横波速度作为数值计算的输入数据,求取了临界点和流体及骨架共计11个弹性参数的具体数值。通过数学方法的计算数据与实验方法的测试数据的比较分析,表明了本文数值计算公式的正确性和实现方法的有效性。本文提出的求取含气介质临界点、流体和骨架弹性参数的“数值计算公式及方法”含义清晰且形式简洁,为孔隙流体介质的数值计算分析和流体属性研究提供了可能的新方法。 相似文献
982.
I.?Jankovi? A.?FioriEmail author G.?Dagan 《Stochastic Environmental Research and Risk Assessment (SERRA)》2003,17(6):384-393
In the present part the results of numerical simulations of flow and transport in media made up from circular inclusions of conductivity K that are submerged in a matrix of conductivity K
0, subjected to uniform mean velocity, are presented. This is achieved for a few values of =K/K
0 (0.01, 0.1 and 10) and of the volume fraction n (0.05, 0.1 and 0.2). The numerical simulations (NS) are compared with the analytical approximate models presented in Part 1: the composite elements (CEA), the effective medium (EMA), the dilute system (DSA) and the first-order in the logconductivity variance (FOA). The comparison is made for the longitudinal velocity variance and for the longitudinal macrodispersivity. This is carried out for n<0.2, for which the theoretical and simulation models represent the same structure of random and independent inclusions distribution. The main result is that transport is quite accurately modeled by the EMA and CEA for low , for which
L
is large, whereas in the case of =10, the EMA matches the NS for n<0.1. The first-order approximation is quite far apart from the NS for the values of examined .
This material is based upon work supported by the National Science Foundation under Grant No. 0218914. Authors also wish to thank the Center of Computational Research, University at Buffalo for assistance in running numerical simulations. 相似文献
983.
借助Christoffel方程可求解出各向异性介质弹性波精确频散关系.利用近似方法进行处理,再通过傅里叶逆变换将频率波数域算子变换为时空域算子,可导出解耦的qP波或qS波波动方程.本文在TTI介质弹性波精确频散关系的基础上,利用近似配方法推导了qP波和qSV波近似频散关系,通过傅里叶逆变换推导了TTI介质qP波和qSV波解耦的波动方程.为了验证近似频散关系的有效性,利用两组模型参数对其进行数值计算,分析了相对误差在不同传播方向上的分布.随后使用有限差分方法分别对均匀、层状及复杂TTI介质弹性波近似解耦波动方程进行数值模拟,结果显示qP波和qSV波完全解耦,并且在各向异性参数η < 0以及介质对称轴倾角变化较大的情况下,纯qP波和纯qSV波近似波动方程依然可以保持稳定.
相似文献984.
985.
986.
987.
R. Ababou 《Stochastic Environmental Research and Risk Assessment (SERRA)》1994,8(2):139-155
This paper investigates analytical solutions of stochastic Darcy flow in randomly heterogeneous porous media. We focus on infinite series solutions of the steady-state equations in the case of continuous porous media whose saturated log-conductivity (lnK) is a gaussian random field. The standard deviation of lnK is denoted . The solution method is based on a Taylor series expansion in terms of parameter , around the value =0, of the hydraulic head (H) and gradient (J). The head solution H is expressed, for any spatial dimension, as an infinite hierarchy of Green's function integrals, and the hydraulic gradient J is given by a linear first-order recursion involving a stochastic integral operator. The convergence of the -expansion solution is not guaranteed a priori. In one dimension, however, we prove convergence by solving explicitly the hierarchical sequence of equations to all orders. An infinite-order stochastic solution is obtained in the form of a -power series that converges for any finite value of . It is pointed out that other expansion methods based on K rather than lnK yield divergent series. The infinite-order solution depends on the integration method and the boundary conditions imposed on individual order equations. The most flexible and general method is that based on Laplacian Green's functions and boundary integrals. Imposing zero head conditions for all orders greater than one yields meaningful far-field gradient conditions. The whole approach can serve as a basis for treatment of higher-dimensional problems. 相似文献
988.
Introduction The method of apparent resistivity with direct current (DC) measurement, adopted from geophysical exploration, is one of the most important precursory approaches in earthquake prediction, in which the geo-electric constitutive model is illustrated by the scalar theory Archies law and correspondingly a set of calculation methods for apparent resistivity of layered media has been established (QIAN, et al, 1985; YAO, 1989). But this is not consistent with the fact that in earthqu… 相似文献
989.
Summary This paper presents a systematic procedure for determining fracture toughness of an anisotropic marble using the diametral
compression test (Brazilian test) with a central crack on the discs. Additionally, a novel formulation to increase the accuracy
in Stress Intensity Factor (SIF) calculations using Boundary Element Method (BEM) is applied to determine the stress intensity
factors and the fracture toughness of anisotropic rocks under mixed-mode loading. The numerical results show that the SIFs
for both isotropic and anisotropic problems are in good agreement with those reported by previous authors. The marble with
clear white-black foliation from Hualien (in eastern Taiwan), was selected for the Brazilian tests. Diametral loading was
conducted on the Cracked Straight Through Brazilian Disc (CSTBD) specimens to evaluate their fracture toughness. In addition,
a new fracture criterion was developed to predict pure mode I, pure mode II or mixed mode (I–II) fracture toughness of the
anisotropic marble. The new fracture criterion is based on the examination of mode I, mode II and mixed mode (I–II) fracture
toughness for different crack angles and anisotropic orientation.
Authors’ address: Associate Professor Chao-Shi Chen, Department of Resources Engineering, National Cheng Kung University,
No. 1 Dasyue Rd., East District, Tainan 701, Taiwan 相似文献
990.
In viscoelastic media, the slowness vector p of plane waves is complex-valued, p = P + iA. The real-valued vectors P and A are usually called the propagation and the attenuation vector, repectively. For P and A nonparallel, the plane wave is called inhomogeneousThree basic approaches to the determination of the slowness vector of an inhomogeneous plane wave propagating in a homogeneous viscoelastic anisotropic medium are discussed. They differ in the specification of the mathematical form of the slowness vector p. We speak of directional specification, componental specification and mixed specification of the slowness vector. Individual specifications lead to the eigenvalue problems for 3 × 3 or 6 × 6 complex-valued matrices.In the directional specification of the slowness vector, the real-valued unit vectors N and M in the direction of P and A are assumed to be known. This has been the most common specification of the slowness vector used in the seismological literature. In the componental specification, the real-valued unit vectors N and M are not known in advance. Instead, the complex-valued vactorial component p
of slowness vector p into an arbitrary plane with unit normal n is assumed to be known. Finally, the mixed specification is a special case of the componental specification with p
purely imaginary. In the mixed specification, plane represents the plane of constant phase, so that N = ±n. Consequently, unit vector N is known, similarly as in the directional specification. Instead of unit vector M, however, the vectorial component d of the attenuation vector in the plane of constant phase is known.The simplest, most straightforward and transparent algorithms to determine the phase velocities and slowness vectors of inhomogeneous plane waves propagating in viscoelastic anisotropic media are obtained, if the mixed specification of the slowness vector is used. These algorithms are based on the solution of a conventional eigenvalue problem for 6 × 6 complex-valued matrices. The derived equations are quite general and universal. They can be used both for homogeneous and inhomogeneous plane waves, propagating in elastic or viscoelastic, isotropic or anisotropic media. Contrary to the mixed specififcation, the directional specification can hardly be used to determine the slowness vector of inhomogeneous plane waves propagating in viscoelastic anisotropic media. Although the procedure is based on 3 × 3 complex-valued matrices, it yields a cumbersome system of two coupled equations. 相似文献