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  • Articles  (14)
  • Porous media  (14)
  • 2010-2014
  • 2000-2004
  • 1990-1994  (8)
  • 1985-1989  (6)
  • 1950-1954
  • Technology  (14)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Shock waves 4 (1994), S. 109-112 
    ISSN: 1432-2153
    Keywords: Combustion ; Detonation ; Porous media
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract In porous media the local elevation of pressure slowly propagates in the adjacent layers of the gas causing the temperature rise there. In the presence of explosive gases this mechanism may lead to the formation of self sustaining combustion waves propagating at a constant speed.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 17 (1994), S. 271-283 
    ISSN: 1573-1634
    Keywords: Porous media ; convection ; layering ; mathematical model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Two-dimensional convective flow in a system of fluid-saturated porous layers is considered for small fluid velocities. The layers are inclined at an angle to the horizontal and there is a temperature gradient across them. A mathematical model of the system is constructed and the resulting series solution is numerically summed. The unique features of this model include its ability to represent non-symmetric multi-layered systems and materials whose permeabilities are anisotropic. The model is applied to various physical configurations. System aspect ratios, system symmetry and permeablity anisotropies are found to influence the effect that layers of different materials have on the convective flow.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Shock waves 3 (1993), S. 105-111 
    ISSN: 1432-2153
    Keywords: Porous media ; Shock compaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Based on experimental results and some additional simplifying assumptions, the general macroscopic two phase equations governing the flow field which is developed in a gas saturated rigid porous medium domain were simplified to a form which enab led us to develop two analytical models for calculating the jump conditions across strong compaction waves. Predictions obtained by these two simplified analytical models are compared to the experimental results of Sandusky and Liddiard (1985) and to predictions of another more complicated model which was proposed by Powers et al. (1989). Fairly good to excelle nt agreements are evident.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 12 (1993), S. 43-54 
    ISSN: 1573-1634
    Keywords: Porous media ; heterogeneous ; rotating flow ; square channel ; Coriolis acceleration ; secondary circulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract An analytical three-dimensional solution to the fluid flow problem through heterogeneous porous media in a rotating square channel is presented. The permeability of the fluid saturated porous domain varies in the vertical direction, thus affecting the imposed main flow in the channel. As a result of Coriolis acceleration, secondary circulation in a plane perpendicular to the main flow direction is created. A particular example of a monotonic distribution of the permeability function is analyzed leading to a single vortex secondary circulation. Nevertheless, multiple vortex secondary flow solutions are possible depending on the particular variation of the permeability in the vertical direction. No secondary motion is expected for isothermal flows in homogeneous porous media.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 9 (1992), S. 49-59 
    ISSN: 1573-1634
    Keywords: Porous media ; mixture theories ; volume fractions ; incompressible constituents ; granular solid matrix ; viscous pore liquid ; finite elastoplasticity ; kinematical hardening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract In this article, porous media theories are referred to as mixture theories extended by the well-known concept of volume fractions. This approach implies the diverse field functions of both the porous solid matrix and the pore fluid to be represented by average functions of the macroscale. The present investigations are based on a binary model of incompressible constituents, solid skeleton, and pore liquid, where, in the constitutive range, use is made of the second-grade character of general heterogeneous media. Within the framework of geometrically finite theories, the paper offers a set of constitutive equations for the solid matrix, the viscous pore liquid and the different interactions between the constituents. The constitutive model applies to saturated as well as to empty solid materials, taking into account the physical nonlinearities based on elasto-plastic solid deformations. In particular, the constitutive model concentrates on granular materials like soil or concrete, where the elastic deformations are usually small and the plastic range is governed by kinematically hardening properties.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 7 (1992), S. 15-38 
    ISSN: 1573-1634
    Keywords: Porous media ; modeling ; scaling ; dimensionless numbers ; dominance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A methodology for eliminating nondominant effects in models that describe transport phenomena in porous media is presented. The methodology is based on the introduction of dimensionless numbers and on a proper evaluation of the order of magnitude of terms. These dimensionless numbers are redefined as characteristics of transport and transformation phenomena in porous media. It is shown that different time scales and different length scales may have to be employed for different variables. A method for evaluating the order of magnitude of the error of prediction when terms are deleted, is presented.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 7 (1992), S. 63-82 
    ISSN: 1573-1634
    Keywords: Porous media ; double porosity ; consolidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We investigate the macroscopic quasi-static description of a deformable porous medium with a double porosity constituted by pores and fractures. For this purpose, we use an homogenization technique which gives the macroscopic modelling from the description at the pore and fracture levels. It appears that the macroscopic description is sensitive to the ratios between the different scales,l/l′ andl′/l″, wherel, l′ l″ are characteristic lengths of the pores, the fractures and the macroscopic medium, respectively. In the first paper we investigate the casel′/l″=(l/l′)2, which exhibits a coupling between the flows through the pores and the fractures. The macroscopic description is shown to depend on a single pressure field and exhibits a broken symmetry. Other situations will be examined in a subsequent paper. Large spectra of pore and fracture sizes are also evoked.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 5 (1990), S. 325-340 
    ISSN: 1573-1634
    Keywords: Porous media ; three-dimensional ; permeability ; random ; fractal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The three-dimensional Stokes flow of a Newtonian fluid through random and/or fractal media is numerically determined. The permeability of these media is derived. Results relative to these structures are presented and discussed. The validity of the Carman equation and of a simple scaling argument is questioned.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 3 (1988), S. 95-106 
    ISSN: 1573-1634
    Keywords: Free convection ; heat transfer ; Porous media ; natural convection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract An analysis is presented for the calculation of heat transfer due to free convective flow along a vertical plate embedded in a porous medium with an arbitrarily varying surface heat flux. By applying the appropriate coordinate transformations and the Merk series, the governing energy equation is expressed as a set of ordinary differential equations. Numerical solutions are presented for these equations which represent universal functions and several computational examples are provided.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 3 (1988), S. 133-144 
    ISSN: 1573-1634
    Keywords: Porous media ; sorptivity ; asymptotic series solution ; unsaturated flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A new asymptotic expansion is proposed for the nonlinear diffusion equation used to model the horizontal infiltration of water into soils. The expansion is based on a small parameter associated with the nonlinearity in the diffusivityD. The expansion leads to simpler integral formulae than previous series solutions and most previous iterative methods. To first order, it yields a formula for sorptivity identical with the ‘double-integration’ result, derived in a less rigorous manner by Parlange (1975). Rigorous conditions for the validity of the asymptotic expansion and the double-integration technique are discussed.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 3 (1988), S. 185-198 
    ISSN: 1573-1634
    Keywords: Porous media ; permeability ; random ; fractal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The transversal Stokes flow of a Newtonian fluid through random and Sierpinski carpets is numerically calculated and the transversal permeability derived. In random carpets derived from site percolation, the average macroscopic permeability varies as (ε- ɛ c)3/2, close to the critical porosityɛ c. This exponent is found to be slightly different from the conductivity exponent. Results for Sierpinski carpets are presented up to the fourth generation. The Carman equation is not verified in these two model porous media.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 2 (1987), S. 521-531 
    ISSN: 1573-1634
    Keywords: Porous media ; high velocity flow ; non-Darcy flow ; Forchheimer equation ; inertial effects ; constitutive equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Experimental observations have established that the proportionality between pressure head gradient and fluid velocity does not hold for high rates of fluid flow in porous media. Empirical relations such as Forchheimer equation have been proposed to account for nonlinear effects. The purpose of this work is to derive such nonlinear relationships based on fundamental laws of continuum mechanics and to identify the source of nonlinearity in equations. Adopting the continuum approach to the description of thermodynamic processes in porous media, a general equation of motion of fluid at the macroscopic level is proposed. Using a standard order-of-magnitude argument, it is shown that at the onset of nonlinearities (which happens at Reynolds numbers around 10), macroscopic viscous and inertial forces are negligible compared to microscopic viscous forces. Therefore, it is concluded that growth of microscopic viscous forces (drag forces) at high flow velocities give rise to nonlinear effects. Then, employing the constitutive theory, a nonlinear relationship is developed for drag forces and finally a generalized form of Forchheimer equation is derived.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 2 (1987), S. 553-569 
    ISSN: 1573-1634
    Keywords: Porous media ; permeability ; random ; fractal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Two-dimensional porous media whose random cross-sections are derived from site percolation are constructed. The longitudinal flow of a Newtonian fluid in the Stokes approximation is then computed and the longitudinal permeability is obtained. Two methods are used and yield the same result when porosity is low. The Carman equation is shown to apply within ±7% when porosity is within the range from 0 to 0.75. Finally, random structures derived from stick percolation are investigated; results are qualitatively the same, but the Carman equation yields a poorer approximation.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 2 (1987), S. 571-596 
    ISSN: 1573-1634
    Keywords: Porous media ; fractal ; permeability ; transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Some geological structures are analysed and found to be fractal. An interesting feature is the very large range of scales involved; the spreading dimension is also measured for some of them. The consequences of these measurements on the analysis of transport processes in porous media are presented - the existence of fractal structures multiplies the variety of actual porous media.
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