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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 3983-3989 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The steady rate of heat conduction Q from a heated sphere maintained at a constant temperature different from that of a surrounding two-phase medium, which consists of an array of spherical particles of thermal conductivity αk and a matrix of conductivity k, is determined by a method of multipole expansion to O(φ4), where φ is the volume fraction of the particles in the array, and by a lubrication analysis for highly conducting and closely packed arrays. The results of the two analyses are combined to obtain estimates of Q that are expected to be accurate over the complete range of α and φ. These results are compared with the predictions of an effective-medium theory, and it is shown that the predictions of this theory are quite accurate over a rather wide range of α, 0〈α〈103, for the case of a simple cubic array, even at its maximum allowable volume fraction, but differ by as much as 60% for the case of a face-centered cubic array.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 2435-2444 
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The method described in Part I [Phys. Fluids 31, XXXX (1988)] is extended to treat the problem of determining the permeability of random arrays of infinitely long cylinders. The results for the transverse and longitudinal permeabilities averaged over several configurations of random arrays of cylinders are presented as a function of the area fraction of the cylinders. A detailed comparison is made with the estimates of the permeability obtained by various approximate and asymptotic theories to determine their range of validity.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2955-2970 
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The motion of bubbles dispersed in a liquid when a small-amplitude oscillatory motion is imposed on the mixture is examined in the limit of small frequency and viscosity. Under these conditions, for bubbles with a stress-free surface, the motion can be described in terms of added mass and viscous force coefficients. For bubbles contaminated with surface-active impurities, the introduction of a further coefficient to parametrize the Basset force is necessary. These coefficients are calculated numerically for random configurations of bubbles by solving the appropriate multibubble interaction problem exactly using a method of multipole expansion. Results obtained by averaging over several configurations are presented. Comparison of the results with those for periodic arrays of bubbles shows that these coefficients are, in general, relatively insensitive to the detailed spatial arrangement of the bubbles. On the basis of this observation, it is possible to estimate them via simple formulas derived analytically for dilute periodic arrays. The effect of surface tension and density of bubbles (or rigid particles in the case where the no-slip boundary condition is applicable) is also examined and found to be rather small.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 21-37 
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The planar singular solutions of Stokes and Laplace equations are derived and applied to a number of transport problems associated with porous surfaces. The velocity, pressure, concentration, and temperature slip coefficients are determined exactly for the semi-infinite periodic arrays of spheres and these are compared with the predictions of two approximate continuum theories formulated by Brinkman [Appl. Sci. Res. A1, 27 (1947)] and Chang and Acrivos [J. Appl. Phys. 59, 375 (1986)] to assess the utility of such theories in accurately predicting various overall properties related to the porous surfaces. It is found that in general these theories provide fairly accurate estimates of these properties even when the length scales based on the relevant macroscopic properties such as the permeability are much smaller than the length scales characterizing the microstructure of the porous media.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 2426-2434 
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A numerical method is developed that takes into account the many-particle interactions in a rigorous manner to determine the effective thermal conductivity Km of a composite medium consisting of parallel circular cylinders of thermal conductivity αk suspended in a matrix of conductivity k. Numerical results for Km are presented for a wide range of α and φ, the area fraction of the cylinders, after averaging over several computer-generated random arrays of cylinders. The results obtained via this exact method are compared with those of various approximate analytical methods to assess their utility in predicting Km.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 1334-1341 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The problem of determining the bulk or effective thermal conductivity of a two-phase composite material whose unit cells contain N(N〉1) spherical particles of thermal conductivity αk suspended in a medium of thermal conductivity k has been treated by extending an earlier analysis of McPhedran and Milton [Appl. Phys. A 26, 207 (1981)] who considered the case N=1. The technique is applied to computer-generated two-phase composites with N=16 whose radial distribution functions approximately satisfy the Percus–Yevick equation. The results, which are presented for a wide range of α and φ (the volume fraction of the spheres), are shown to be in good agreement with the experimental values of conductivity of fluidized beds reported by Turner [Chem. Eng. Sci. 31, 487 (1976)].
    Materialart: Digitale Medien
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