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  1. Article

    Open Access

    Percolativity of Porous Media

    Connectivity and connectedness are nonadditive geometric functionals on the set of pore scale structures. They determine transport of mass, volume or momentum in porous media, because without connectivity ther...

    R. Hilfer, J. Hauskrecht in Transport in Porous Media (2022)

  2. Article

    Open Access

    A Brief Review of Capillary Number and its Use in Capillary Desaturation Curves

    Capillary number, understood as the ratio of viscous force to capillary force, is one of the most important parameters in enhanced oil recovery (EOR). It continues to attract the interest of scientists and eng...

    Hu Guo, Kao** Song, R. Hilfer in Transport in Porous Media (2022)

  3. Article

    Open Access

    Effective transport coefficients of anisotropic disordered materials

    A novel effective medium theory for homogenized transport coefficients of anisotropic mixtures of possibly anisotropic materials is developed. Existing theories for isotropic systems cannot be easily extended,...

    R. Hilfer, J. Hauskrecht in The European Physical Journal B (2022)

  4. Article

    Open Access

    On extremal domains and codomains for convolution of distributions and fractional calculus

    It is proved that the class of c-closed distribution spaces contains extremal domains and codomains to make convolution of distributions a well-defined bilinear map**. The distribution spaces are systematica...

    T. Kleiner, R. Hilfer in Monatshefte für Mathematik (2022)

  5. Article

    Open Access

    Fractional glassy relaxation and convolution modules of distributions

    Solving fractional relaxation equations requires precisely characterized domains of definition for applications of fractional differential and integral operators. Determining these domains has been a longstand...

    T. Kleiner, R. Hilfer in Analysis and Mathematical Physics (2021)

  6. Article

    Open Access

    Convolution operators on weighted spaces of continuous functions and supremal convolution

    The convolution of two weighted balls of measures is proved to be contained in a third weighted ball if and only if the supremal convolution of the corresponding two weights is less than or equal to the third ...

    T. Kleiner, R. Hilfer in Annali di Matematica Pura ed Applicata (1923 -) (2020)

  7. No Access

    Article

    Stable Propagation of Saturation Overshoots for Two-Phase Flow in Porous Media

    Propagation of saturation overshoots for two-phase flow of immiscible and incompressible fluids in porous media is analyzed using different computational methods. In particular, it is investigated under which ...

    M. Schneider, T. Köppl, R. Helmig, R. Steinle, R. Hilfer in Transport in Porous Media (2018)

  8. Article

    Erratum to: Non-monotonic Travelling Wave Fronts in a System of Fractional Flow Equations from Porous Media

    O. Hönig, P. A. Zegeling, F. Doster, R. Hilfer in Transport in Porous Media (2016)

  9. Article

    Open Access

    Non-monotonic Travelling Wave Fronts in a System of Fractional Flow Equations from Porous Media

    Motivated by observations of saturation overshoot, this article investigates generic classes of smooth travelling wave solutions of a system of two coupled nonlinear parabolic partial differential equations re...

    O. Hönig, P. A. Zegeling, F. Doster, R. Hilfer in Transport in Porous Media (2016)

  10. No Access

    Article

    Influence of Initial Conditions on Propagation, Growth and Decay of Saturation Overshoot

    A sequence of drainage and imbibition shocks within the traditional theory of two-phase immiscible displacement can give rise to shallow non-monotone saturation profiles as shown in Hilfer and Steinle (Eur Phy...

    R. Steinle, R. Hilfer in Transport in Porous Media (2016)

  11. No Access

    Article

    Saturation overshoot and hysteresis for twophase flow in porous media

    Saturation overshoot and hysteresis for two phase flow in porous media are briefly reviewed. Old and new challenges are discussed. It is widely accepted that the traditional Richards model for twophase flow in...

    R. Hilfer, R. Steinle in The European Physical Journal Special Topics (2014)

  12. Article

    Open Access

    Traveling Wave Solutions in a Generalized Theory for Macroscopic Capillarity

    One-dimensional traveling wave solutions for imbibition processes into a homogeneous porous medium are found within a recent generalized theory of macroscopic capillarity. The generalized theory is based on th...

    O. Hönig, F. Doster, R. Hilfer in Transport in Porous Media (2013)

  13. No Access

    Chapter and Conference Paper

    Applications and Implications of Fractional Dynamics for Dielectric Relaxation

    This article summarizes briefly the presentation given by the author at the NATO Advanced Research Workshop on “Broadband Dielectric Spectroscopy and its Advanced Technological Applications”, held in Perpignan...

    R. Hilfer in Recent Advances in Broadband Dielectric Spectroscopy (2013)

  14. No Access

    Article

    Percolation as a Basic Concept for Macroscopic Capillarity

    The concepts of relative permeability and capillary pressure are crucial for the accepted traditional theory of two phase flow in porous media. Recently, a theoretical approach was introduced that does not req...

    R. Hilfer, F. Doster in Transport in Porous Media (2010)

  15. No Access

    Article

    Review on Scale Dependent Characterization of the Microstructure of Porous Media

    The paper discusses local porosity theory and its relation with other geometric characterization methods for porous media such as correlation functions and contact distributions. Special emphasis is placed on ...

    R. Hilfer in Transport in Porous Media (2002)

  16. No Access

    Chapter and Conference Paper

    Effective Physical Properties of Sandstones

    In this paper we continue the investigation of the effective transport parameters of a digitized sample of Fontainebleau sandstone and three reconstruction models discussed previously in Biswal et. al., Physic...

    J. Widjajakusuma, R. Hilfer in IUTAM Symposium on Theoretical and Numeric… (2002)

  17. No Access

    Chapter and Conference Paper

    Fractional Evolution Equations and Irreversibility

    The paper reviews a general theory predicting the general importance of fractional evolution equations. Fractional time evolutions are shown to arise from a microscopic time evolution in a certain long time sc...

    R. Hilfer in Traffic and Granular Flow ’99 (2000)

  18. No Access

    Chapter and Conference Paper

    On fractional diffusion and its relation with continuous time random walks

    Time evolutions whose infinitesimal generator is a fractional time derivative arise generally in the long time limit. Such fractional time evolutions are considered here for random walks. An exact relationship...

    R. Hilfer in Anomalous Diffusion From Basics to Applications (1999)

  19. No Access

    Chapter and Conference Paper

    Fractional Derivatives in Static and Dynamic Scaling

    A derivative or integral of fractional order is usually defined by analytically continuing a suitable definition of the derivative or integral of integer order n ∈ ℕ to real or complex values of n.

    R. Hilfer in Scale Invariance and Beyond (1997)

  20. No Access

    Article

    Dimensional analysis of pore scale and field scale immiscible displacement

    A basic re-examination of the traditional dimensional analysis of microscopic and macroscopic multiphase flow equations in porous media is presented. We introduce a ‘macroscopic capillary number’ ...

    R. Hilfer, P. E. Øren in Transport in Porous Media (1996)

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