共查询到20条相似文献,搜索用时 15 毫秒
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Experimental data for rupture lines and wetting fronts in various kinds of paper suggest that the scaling properties of interfaces pinned in such fractally correlated media are governed by the fractal dimension, D, of the medium. Specifically, the phenomenological relation zeta=D-(d-1), where d is the spatial dimension of the system, satisfactorily describes the local roughness exponent, zeta, of a pinned interface. The relation is supported by analysis of the competition between an elastic restoring force and correlated pinning force in an elastic fractal media, under the assumption that the pinning force correlations decaying with distance, r, as r(-eta) with 0相似文献
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V. N. Belyi V. L. Malevich Yu. Shraiber N. A. Khilo 《Journal of Applied Spectroscopy》2008,75(2):199-202
Monte-Carlo simulation of light propagation in a porous medium with a mass fractal morphology was carried out. It was shown
that the simulation results can be used to analyze experimental data on light scattering and to study the porous medium structure.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 193–196, March–April, 2008. 相似文献
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Based on a lattice Boltzmann method and general principles of porous flow, a numerical technique is presented for analysing the separation of multi-phase immiscible fluids in porous media. The total body force acting on fluid particles is modified by axiding relative permeability in Nithiarasu's expression with an axiditional surface tension term. As a test of this model, we simulate the phase separation for the case of two immiscible fluids. The numerical results show that the two coupling relative permeability coefficients K12 and K21 have the same magnitude, so the linear flux-forcing relationships satisfy Onsager reciprocity. Phase separation phenomenon is shown with the time evolution of density distribution and bears a strong similarity to the results obtained from other numerical models and the flows in sands. At the same time, the dynamical rules in this model are local, therefore it can be run on massively parallel computers with well computational efficiency. 相似文献
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《中国物理 B》2020,(5)
The fractal Brownian motion is utilized to describe pore structures in porous media. A numerical model of laminar flow in porous media is developed, and the flow characteristics are comprehensively analyzed and compared with those of homogeneous porous media. Moreover, the roles of the fractal dimension and porosity in permeability are quantitatively described. The results indicate that the pore structures of porous media significantly affect their seepage behaviors. The distributions of pressure and velocity in fractal porous media are both non-uniform; the streamline is no longer straight but tortuous. When Reynolds number Re 1, the dimensionless permeability is independent of Reynolds number, but its further increase will lead to a smaller permeability. Moreover, due to the higher connectivity and enlarged equivalent aperture of internal channel network, the augment in porosity leads to the permeability enhancement, while it is small and insensitive to porosity variation when ε 0.6. Fractal dimension also plays a significant role in the permeability of porous media. The increase in fractal dimension leads to the enhancement in pore connectivity and a decrease in channel tortuosity,which reduces the flow resistance and improves the transport capacity of porous media. 相似文献
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We present a numerical study on the dynamics of imbibition fronts in porous media using a pipe network model. This model quantitatively reproduces the anomalous scaling behavior found in imbibition experiments [Phys. Rev. E 52, 5166 (1995)]. Using simple scaling arguments, we derive a new identity among the scaling exponents in agreement with the experimental results. 相似文献
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《Journal of Electrostatics》2014,72(6):441-446
An analytical expression for the streaming current in fractal porous media is developed based on the capillary model and the fractal theory for porous media. The proposed fractal model is expressed as a function of the space charge density at the solid–liquid interface, the fluid flow rate, the Debye–Huckel parameter, the minimum and maximum pore/capillary radii and fractal dimensions for porous media. The results are compared with available experimental data and good agreement is found between them. In addition, factors influencing the streaming current in porous media are also analyzed. 相似文献
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W. G. Laidlaw G. R. Hamilton R. B. Flewwelling W. G. Wilson 《Journal of statistical physics》1988,53(3-4):713-731
Percolation invasion displacement of a compressible defender is examined for two cases: when only the smallest accessible site is entered at each step and when all accessible sites less than the size given by a reducing back pressure are entered at each time step. Although the fractions of invading fluid are different, their scaling properties are equivalent. The effect of limited control of a back pressure in a real displacement and the effect of viscosity in a real time displacement are examined. In these cases the scaling properties of a percolation process at breakthrough are removed. As a result, one should expect that realistic displacement models will not have the singular properties usually attributed to percolation processes. 相似文献
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Analysis of small-angle scattering data, as well as novel precipitation measurements, are used to delineate the structure of the molecular aggregates that are formed when a fluid is injected into a porous medium to displace the in-place fluid. Our analysis suggests conclusively that these aggregates are fractal formed by diffusion-limited processes. The implications for the molecular weight distribution of the aggregates and modelling their flow and precipitation in a porous medium are discussed. 相似文献
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C. Casieri C. De Angelis F. De Luca G. Garreffa B. Maraviglia 《Applied magnetic resonance》1993,4(3):357-365
Low field Magnetic Resonance Imaging is used to study oil diffusion in a wet soil model. A complete discrimination between oil and water has been obtained by using Inversion-Recovery pulse sequence. The time evolution of the oil image gives the parameters which describe the dense fluid diffusion rate in the whole space directions. 相似文献
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Pulsed field gradient nuclear magnetic resonance (PFG-NMR) and NMR imaging were used to study temporal and spatial domains of an electrokinetically-driven mobile phase through open and packed segments of capillaries. Characteristics like velocity distribution and an asymptotic dispersion are contrasted to viscous flow behavior. We show that electroosmotic flow in microchannel geometries can offer a significant performance advantage over the pressure-driven flows at comparable Peclét numbers, indicating that velocity extremes in the pore space of open tubes and packed beds are drastically reduced. An inherent problem of capillary electrochromatography that we finally address is the existence of wall effects when in the general case the surface zeta-potentials of the capillary inner wall and the adsorbent particles are different. Using dynamic NMR microscopy we were able resolve this systematic velocity inequality of the flow pattern which strongly influences axial dispersion and may be responsible for long time-tails of velocity distribution in the mobile phase. 相似文献
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In this paper we address the question of the existence of a well defined, non-trivial fractal dimensionD of self-affine clusters. In spite of the obvious relevance of such clusters to a wide range of phenomena, this problem is still open since thedifferent published predictions forD have not been tested yet. An interesting aspect of the problem is that a nontrivial global dimension for clusters is in contrast with the trivial global dimension of self-affine functions. As a much studied example of self-affine structures, we investigate the infinite directed percolation cluster at the threshold. We measuredD ind=2 dimensions by the box counting method. Using a correction to scaling analysis, we obtainedD=1.765(10). This result does not agree with any of the proposed relations, but it favorsD=1+(1-
)/
, where
and
are the correlation length exponents and is a Fisher exponent in the cluster scaling. 相似文献
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Vergara L 《Physical review letters》2005,95(10):108002
The scattering of nonlinear solitary waves from an interface is numerically studied in detail. The interface is created by joining two one-dimensional chains of spherical beads of different radii (masses). Beads are assumed to be in Hertzian contact, without static precompression, and to have identical mechanical properties. In addition to previous findings, it is observed that in both cases, when a solitary wave travels from the light to the heavy system and vice versa, secondary multipulse structures are generated at the interface, being backscattered and forward scattered, respectively. 相似文献
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H. Eugene Stanley 《Journal of statistical physics》1984,36(5-6):843-860
We consider the application of fractal concepts to polymer statistics and to anomalous transport in randomly porous media. It is found that answers to interesting physics questions can be expressed in terms of several new fractal dimensions (in addition to the fractal dimensiond
f
): (1)d
f
BB
, the fractal dimension of the backbone, arises in connection with electric current flow, (2)d
red, the fractal dimension of the singly connected bonds in the backbone, arises in connection with its equivalence to the thermal scaling power, (3)d
E, the fractal dimension of the of the elastic backbone, (4)d
u, the fractal dimension of the unscreened perimeter, arises in connection with the viscosity singularity at the gelation threshold, (5)d
min the fractal dimension of the minimum path (or chemical distance) between two sites, arises in co-nnection with the Aharony-Stauffer conjecture, (6)dw, the fractal dimension of a random walk, (7)d
G, the fractal dimension of growth sites that arise as a random walk creates a cluster. Relations among these fractal dimensions are discussed, some of which can be proved and others of which are conjectures whose validity has been established only in certain limiting cases.Supported in part at the Center for Polymer Studies by grants from ONR and NSF. 相似文献
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Using the principle of diffusion-limited aggregation(DLA),a new model is introduced to simulate the displacement of one fluid by another in porous media.The results agree with experiments.apparently they do not leave out film-flow phenomena.Simultaneously,we also present a new numerical method to treat our results by the lattice Boltzmann method(LBM),All these will be helpful for analysing similar subjects. 相似文献