Dynamics of acoustic waves in porous media saturated with gas-vapor mixture

Wave processes in wet porous media saturated with gas-vapor mixture have been studied with allowance for interphase interaction forces and heat and mass exchange between the skeleton of the porous medium and the gas-vapor mixture. Dispersion relations have been obtained for a porous medium saturated with gas-vapor mixture, vapor, or gas.     

A phase field model for the freezing saturated porous medium

In terms of the mixture theory and phase field theory, a phase field model is developed for the saturated porous medium undergoing phase transition. In the proposed model, it is postulated that during the phase transition of the porous medium, both the solid skeleton and pore fluid will undergo phase transition. The phase states of the solid skeleton and pore fluid are characterized by respective order parameters. To simplify the proposed phase field model, the temperatures and order parameters of the solid skeleton and pore fluid are assumed to be equal. The balance laws of the porous medium are given by the conventional mixture theory. The order parameter and the porosity of the porous medium are considered as internal variables and their evolution equations are determined by the entropy inequality of the porous medium. The constitutive representations for the stresses, entropies, heat fluxes, drag force and the evolution equations for the order parameter and porosity are derived by exploitation of the entropy inequality. To illustrate the proposed model, a concrete phase field model for the freezing porous medium is established in the paper. In the model, the memory effect associated with phase transition of the porous medium is taken into account by assuming Stieltjes integral for the strain energy of the porous medium. The constitutive representations for the above variables are then derived according to the proposed free energy expression for the porous medium. Finally, the boundary condition associated with the proposed model and the determination of some parameters involved in our model are discussed in the paper briefly.     

Acceleration waves in elastic-plastic porous media: Interlacing and separation properties

For a porous medium with an elastic-plastic solid skeleton that obeys an associative plastic flow rule, the squares of the elastic and plastic acceleration wave-speeds are shown to interlace. Moreover when they are real, the wave-speeds of the underlying drained solid are proved to separate the wave-speeds of the porous medium.     

Nonlinear filtration in cracked porous materials

Stationary filtration to a well and to a gallery in a cracked porous medium is investigated with the strong dependence of structural-mechanical properties of the medium on the pressure of the filtering fluid being taken into account.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 6, pp. 943–950, June, 1985.     

Absorptive capacity of powders

The change in pressure during gas desorption from the clayey material of the skeleton of a porous medium is examined. It is shown that absorptive capacity of the powder can be determined from pressure measurements.     

A coupled discrete element‐finite difference approach for modeling mechanical response of fluid‐saturated porous materials

A model of fluid‐saturated poroelastic medium was developed based on a combination of the discrete element method and grid method. The developed model adequately accounts for the deformation, fracture, and multiscale internal structure of a porous solid skeleton. The multiscale porous structure is taken into account implicitly by assigning the porosity and permeability values for the enclosing skeleton, which determine the rate of filtration of a fluid. Macroscopic pores and voids are taken into account explicitly by specifying the computational domain geometry. The relationship between the stress–strain state of the solid skeleton and pore fluid pressure is described in the approximations of simply deformable discrete element and Biot's model of poroelasticity. The developed model was applied to study the mechanical response of fluid‐saturated samples of brittle material. Based on simulation results, we constructed a generalized logistic dependence of uniaxial compressive strength on loading rate, mechanical properties of fluid and enclosing skeleton, and on sample dimensions. The logistic form of the generalized dependence of strength of fluid‐saturated elastic–brittle porous materials is due to the competition of two interrelated processes, such as pore fluid pressure increase under solid skeleton compression and fluid outflow from the enclosing skeleton to the environment. Copyright © 2015 John Wiley & Sons, Ltd.     

Macroscopic Pressure Filtration Field in a Medium with Double Porosity

Journal of Engineering Physics and Thermophysics - This article presents a mathematical model of the pressure filtration field in a porous medium with a skeleton formed by two solid phases of...     

Propagation and decay of acceleration waves in thermoconsolidating media

Summary The propagation of acceleration waves in a fluid-saturated porous medium is considered. The two-phase medium is the system consisting of a porous elastic solid skeleton, filled with a viscous compressible fluid. Two types of the media are taken into account: the medium composed of definite conductors and the medium composed of non-conductors. The method of singular surfaces has been used in these considerations. The acceleration waves in the medium consisting of non-conductors are not homentropic, in general. In this paper the conditions are determined which must be fulfilled to satisfy the acceleration waves to be homentropic.The propagation conditions of the waves are formulated and analysed. As usual in such a two-phase medium two longitudinal waves and one transverse wave are propagated. The growth equations of homothermal and homentropic waves are derived, and their solutions are analysed.     

Propagation of waves in a fluid-saturated porous elastic solid

A theory is developed for the propagation of waves in a porous elastic solid containing a compressible viscous fluid using a homogenization process. The matrix is a lattice of periodically distributed gaps of arbitrary shape, the period of the lattice being small compared with the wave length. The present treatment is concerned with materials where fluid and solid are of comparable densities. Two cases are considered: the situation in which the pores are connected and that in which they are not. When pores are closed, the bulk medium behaves like an elastic medium; when they are connected, the fluid filtration and the bulk deformation are coupled. Boundary conditions, for macroscopic variables, at the interface between such a porous medium and the adjacent free flow are given.     

The propagation of linear waves in humid,gas-saturated media

The process of propagation of acoustic waves in humid, gas-saturated porous media is investigated in a two-velocity approximation. A dispersion relation is derived, which includes interphase interaction forces and heat transfer between the skeleton of porous medium, liquid, and gas. The effect of heat transfer between the phases on the propagation of the “fast” and “slow” waves is included by means of heat equation     

Effects of Stress and Pore Pressure on Deformation of a Thin Crack-Like Inhomogeneity in a Poroelastic Medium

The influence of applied stresses and internal fluid pressure on deformation of a flat ellipsoidal inhomogeneity in a homogeneous poroelastic medium is studied. The inhomogeneity is filled with a porous material having a skeleton much softer than the corresponding to the surrounding medium (crack-like inclusion). The result of the calculation of stress and strain fields inside such inclusion is presented. Explicit formulas for the inclusion aspect ratio changing are obtained. They are relevant for velocities of seismic waves in porous rocks (Toksöz et al, 1976) their permeability (Gibson &; Toksöz, 1990) as functions of confining and pore pressures. Results are compared with the ones available in literature.     

A formulation for an unsaturated porous medium undergoing large inelastic strains

 This paper presents a formulation for a saturated and partially saturated porous medium undergoing large elastic or elastoplastic strains. The porous material is treated as a multiphase continuum with the pores of the solid skeleton filled by water and air, this last one at constant pressure. This pressure may either be the atmospheric pressure or the cavitation pressure. The governing equations at macroscopic level are derived in a spatial and a material setting. Solid grains and water are assumed to be incompressible at the microscopic level. The isotropic elastoplastic behaviour of the solid skeleton is described by the multiplicative decomposition of the deformation gradient into an elastic and a plastic part. The effective stress state is limited by the Drucker-Prager yield surface, for which a particular “apex formulation” is advocated. The water is assumed to obey Darcy's law. Numerical examples of strain localisation of dense and loose sand conclude the paper. Received 15 March 2001     

A numerical contact algorithm in saturated porous media with the extended finite element method

In this paper, a coupled hydro-mechanical formulation is developed for deformable porous media subjected to crack interfaces in the framework of extended finite element method. Governing equations of the porous medium consist of the momentum balance of the bulk together with the momentum balance and continuity equations of the fluid phase, known as formulation. The discontinuity in fractured porous medium is modeled for both opening and closing modes that results in the fluid flow within the fracture, and/or contact behavior at the crack edges. The fluid flow through the fracture is assumed to be viscous and is modeled by employing the Darcy law in which the permeability of fracture is obtained using the cubic law. The contact condition in fractured porous medium is handled by taking the advantage from two different algorithms of LATIN method and penalty algorithm. The effect of contact on fluid phase is employed by considering no leak-off from/into the porous medium. The nonlinearity of coupled equations produced due to opening and closing modes is carried out using an iterative algorithm in the Newton–Raphson procedure. Finally, several numerical examples are solved to illustrate the performance of proposed X-FEM method for hydro-mechanical behavior of fractured porous media with opening and closing modes.     

仿生制备多孔ZrC/C复合陶瓷材料

以碳化后的梧桐木块作为碳模板,采用金属锆作为锆源,在KCl和KF的混合熔盐体系中制备了多孔ZrC/C复合陶瓷材料。研究了不同碳化温度对碳模板的显微形貌、显气孔率和体积密度的影响。并采用X射线光电子能谱(XPS)、傅里叶变换红外光谱(FTIR)、X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征了梧桐木的碳化过程以及复合材料的物相组成和显微形貌。结果表明:梧桐木的碳化分为有机物的热分解和石墨化两个过程;碳化后的梧桐木保留了多孔的特征结构,随着碳化温度的升高,碳模板显气孔率变大,体积密度减小;反应时间的延长有利于增强ZrC层与碳模板基体表面的结合力;KF的加入量需要严格控制,过量的KF会破坏复合材料的结构。     

一维分数导数粘弹性饱和多孔介质层的稳态响应

固相骨架的应力-应变关系利用分数导数粘弹性Kelvin 模型来描述,在流相和固相微观不可压以及小变形的假定下建立了分数导数粘弹性饱和多孔介质层一维稳态响应的数学模型和运动控制方程,求得了分数导数粘弹性饱和多孔介质层一维稳态响应的固相位移和液相位移。通过数值算例分析了分数导数的阶数对稳态响应的影响。研究结果表明:固相位移和液相位移随频率的增大逐渐趋于零,在低频时,分数导数的阶数越大固相位移和液相位移越大。     

Filtration Combustion in Hydrocarbon Desorption from a Porous Medium

We have investigated theoretically and experimentally the process of filtration combustion with hydrocarbon desorption from a porous skeleton realized, in particular, in heat cleaning of porous media out of residues of organic impurities. The problem on the wave of such a combustion in a system with three phases — gaseous, liquid, and inert solid — has been solved analytically. The specific features of this process as compared to the traditional process of filtration combustion of gases have been revealed. The dependences of the basic characteristics of the waves on the content of methane in the gas mixture as well as of oil and water in a porous medium have been obtained. A comparison with the experimental data has been made. Recommendations for optimizing the operation of decontamination plants on the basis of the process considered are given.     

饱和多孔介质中动力渗流耦合分析的Biot-Cosserat连续体模型与应变局部化有限元模拟

提出了适用于饱和多孔介质中应变局部化分析及动力渗流耦合分析的Biot-Cosserat连续体模型。基于饱和多孔介质动力渗流耦合分析的Biot理论,将固体骨架看作Cosserat连续体,并考虑旋转惯性,建立了饱和多孔介质动力渗流耦合分析的Biot-Cosserat连续体模型。基于Galerkin加权余量法,对所发展的模型推导了以固体骨架广义位移(包含旋转)及孔隙水压力为基本未知量的有限元公式。利用所发展的数值模型,对包含压力相关弹塑性固体骨架材料的饱和多孔介质进行了动力渗流耦合分析与应变局部化有限元模拟,结果表明,所发展的两相饱和多孔介质动力渗流耦合分析的Biot-Cosserat连续体模型能保持饱和两相介质应变局部化问题的适定性及模拟饱和多孔介质中由应变软化引起的应变局部化现象的有效性。     

A numerical model for immiscible two-phase fluid flow in a porous medium and its time domain solution

The governing equations for the interaction of two immiscible fluids within a deforming porous medium are formulated on the basis of generalized Biot theory. The displacement of the solid skeleton, the pressure and saturation of wetting fluid are taken as primary unknowns of the model. The finite element method is applied to discretize the governing eqations in space. The time domain numerical solution to the coupled problem is achieved by using an unconditionally stable direct integration procedure. Examples are presented to illustrate the performance and capability of the approach.