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  • 1
    Digitale Medien
    Digitale Medien
    Flow of Maxwell fluids in porous media (1996)
    Springer
    Transport in porous media 25 (1996), S. 167-192 
    Details
    ISSN: 1573-1634
    Schlagwort(e): elastic fluid ; volume averaging ; closure ; Darcy's law ; dynamic permeability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract In this paper we analyze the flow of a Maxwell fluid in a rigid porous medium using the method of volume averaging. We first present the local volume averaged momentum equation which contains Darcy-scale elastic effects and undetermined integrals of the spatial deviations of the pressure and velocity. A closure problem is developed in order to determine the spatial deviations and thus obtain a closed form of the momentum equation that contains a time-dependent permeability tensor. To gain some insight into the effects of elasticity on the dynamics of flow in porous media, the entire problem is transformed to the frequency domain through a temporal Fourier transform. This leads to a dynamic generalization of Darcy's law. Analytical results are provided for the case in which the porous medium is modeled as a bundle of capillary tubes, and a scheme is presented to solve the transformed closure problem for a general microstructure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00135854
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  • 2
    Digitale Medien
    Digitale Medien
    Extended irreversible thermodynamics as a framework for transport phenomena in porous media (1992)
    Springer
    Transport in porous media 9 (1992), S. 207-221 
    Details
    ISSN: 1573-1634
    Schlagwort(e): Nonequilibrium thermodynamics ; thermal waves ; Darcy-Brinkman law ; Forchheimer correction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract A theoretical extended thermodynamic approach to describe transport in porous media is presented. For a particular model of the porous medium, approximate time evolution equations for the fluxes in the system are derived. The use of these equations is illustrated by considering three different transport problems. A finite velocity for the propagation of thermal disturbances within the medium is predicted in the case of heat transport in a system where the effective porosity is zero. Also, a generalization of the Darcy-Brinkman law that incorporates thermal effects, independently of the presence of external forces, arises when consideration is given to the combined mass and heat transport problem. Finally, for the isothermal transport of fluid, the thermodynamic framework provides a possible interpretation of the origin and the role played by both the Brinkman and the Forchheimer corrections to Darcy's law.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00611967
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  • 3
    Digitale Medien
    Digitale Medien
    Chapman-Enskog velocity distribution for tracer diffusion (1989)
    Springer
    Journal of statistical physics 57 (1989), S. 907-920 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Chapman-Enskog method ; tracer diffusion ; velocity distribution function
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The Chapman-Enskog method is used to obtain an approximate velocity distribution function for tracer diffusion in dilute hard-sphere mixtures. Different ratios of the mass of the tracer to that of the excess component (including the well-known limiting cases of the Lorentz and the Rayleigh models) are considered and the corresponding diffusion coefficients are also evaluated. A comparison with the recent results of Tompson and Loyalka for both the diffusion coefficients and the distribution functions provides a perspective on the usefulness and nature of the approximate method.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01022840
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  • 4
    Digitale Medien
    Digitale Medien
    On the foundations of extended irreversible thermodynamics (1984)
    Springer
    Journal of statistical physics 37 (1984), S. 465-484 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Extended irreversible thermodynamics ; kinetic theory ; fluctuations ; memory functions ; projection operators ; flux relaxation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A theory of macroscopic systems which takes as independent variables the slow (conserved) ones plus the fast dissipative fluxes is carefully analyzed at three levels of description: macroscopic (thermodynamic), microscopic (projection operators) and mesoscopic (fluctuation theory). Such a description is compared with the memory function approach based only on the conserved variables. We find that the first theory is richer and wider than the second one, and some misunderstandings in this connection are clarified and discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01011845
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  • 5
    Digitale Medien
    Digitale Medien
    Hydrodynamic interactions of dilute polymer solutions in elongational flow (1991)
    Springer
    Journal of statistical physics 62 (1991), S. 1255-1266 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Dilute polymer solutions ; dumbbell model ; hydrodynamic interactions ; rheological properties ; elongational flows
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Dumbbell models are only crude representations of actual polymer molecules, but their simplicity allows for explicit calculations which in many instances have shed light on the connection between molecular properties and rheological behavior. On the other hand, hydrodynamic interactions are known to strongly influence the dynamic response of polymer solutions and this makes the representation of the hydrodynamic drag an important aspect in the calculations. In the present work, the effects of the state of flow are incorporated explicitly in the frictional properties of the FENE model of a dilute polymer solution. Results for the steady elongational viscosity and the mean square end-to-end distance arc presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01128186
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  • 6
    Digitale Medien
    Digitale Medien
    Transport coefficients of fluid mixtures (1986)
    Springer
    International journal of thermophysics 7 (1986), S. 851-861 
    Details
    ISSN: 1572-9567
    Schlagwort(e): kinetic theory ; mixtures ; numerical results ; transport coefficients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract On the basis of the successful description of the equilibrium properties of simple fluids and fluid mixtures using perturbation theory, the consequences of including density- and temperature-dependent diameters in the formulas for the transport coefficients of dense hard-sphere fluid mixtures are investigated. The advantages and limitations of this approach for the correlation of the experimental data of real mixtures, together with numerical estimates for particular mixtures, are discussed. On the other hand, recent mean field kinetic theories which include the effect of the attractive tail in the intermolecular potential are employed to derive transport coefficients for mixtures. Numerical results are presented and comparison with other theories is also made.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00503842
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  • 7
    Digitale Medien
    Digitale Medien
    A simple model illustrative of some features of polymer dynamics (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 2215-2236 
    Details
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A quasi-one-dimensional model for the dynamics of a polymer in dilute solution is described. The diffusion equation in the presence of energy barriers to conformational change is solved approximately for the case of high barriers, by a method closely analogous to the method of configuration interaction in molecular quantum mechanics. The dynamic shear viscosity is calculated in terms of the model and the ultrasonic absorption is discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1978.180161209
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