Research Project A03

Development of interface concepts using averaging techniques


Data sets published by project A03 can be found on the DaRUS website

Publications in scientific journals

  1. Conference papers

    1. Strohbeck, P., Riethmüller, C., Göddeke, D., & Rybak, I. (2023). Robust and Efficient Preconditioners for Stokes--Darcy Problems. In E. Franck, J. Fuhrmann, V. Michel-Dansac, & L. Navoret (Eds.), Finite Volumes for Complex Applications X---Volume 1, Elliptic and Parabolic Problems (pp. 375--383). Springer Nature Switzerland.
    2. Eggenweiler, E., Nickl, J., & Rybak, I. (2023). Justification of Generalized Interface Conditions for Stokes--Darcy Problems. In E. Franck, J. Fuhrmann, V. Michel-Dansac, & L. Navoret (Eds.), Finite Volumes for Complex Applications X---Volume 1, Elliptic and Parabolic Problems (pp. 275--283). Springer Nature Switzerland.
    3. Eggenweiler, E., & Rybak, I. (2020). Interface Conditions for Arbitrary Flows in Coupled Porous-Medium and Free-Flow Systems. In R. Klöfkorn, E. Keilegavlen, F. Radu, & J. Fuhrmann (Eds.), Finite Volumes for Complex Applications IX - Methods,Theoretical Aspects, Examples (Vol. 323, pp. 345--353). Springer International Publishing.
  2. (Journal-) Articles

    1. Mohammadi, F., Eggenweiler, E., Flemisch, B., Oladyshkin, S., Rybak, I., Schneider, M., & Weishaupt, K. (2023). A surrogate-assisted uncertainty-aware Bayesian validation framework and its application to coupling free flow and porous-medium flow. Computational Geosciences.
    2. Kröker, I., Oladyshkin, S., & Rybak, I. (2023). Global sensitivity analysis using multi-resolution polynomial chaos expansion for coupled Stokes--Darcy flow problems. Computational Geosciences.
    3. Strohbeck, P., Eggenweiler, E., & Rybak, I. (2023). A Modification of the Beavers--Joseph Condition for Arbitrary Flows to the Fluid--porous Interface. Transport in Porous Media, 147(3), Article 3.
    4. Eggenweiler, E., Discacciati, M., & Rybak, I. (2022). Analysis of the Stokes-Darcy problem with generalised interface conditions. ESAIM: Mathematical Modelling and Numerical Analysis, 56, 727–742.
    5. Eggenweiler, E., & Rybak, I. (2021). Effective coupling conditions for arbitrary flows in Stokes-Darcy systems. Multiscale Modeling and Simulation, 19(2), Article 2.
    6. Wagner, A., Eggenweiler, E., Weinhardt, F., Trivedi, Z., Krach, D., Lohrmann, C., Jain, K., Karadimitriou, N., Bringedal, C., Voland, P., Holm, C., Class, H., Steeb, H., & Rybak, I. (2021). Permeability Estimation of Regular Porous Structures: A Benchmark for Comparison of Methods. Transport in Porous Media, 138, 1–23.
    7. Rybak, I., Schwarzmeier, C., Eggenweiler, E., & Rüde, U. (2021). Validation and calibration of coupled porous-medium and  free-flow problems using pore-scale resolved models. Comput. Geosci., 25, 621--63.
    8. Eggenweiler, E., & Rybak, I. (2020). Unsuitability of the Beavers–Joseph interface condition for filtration problems. Journal of Fluid Mechanics, 892, A10. 10.1017/jfm.2020.194


Coupled macroscale problem with arbitrary flows to the interface.

About this Project

New, more general interface conditions, which are valid for arbitrary flows in coupled free-flow and porous-medium systems, are required since classical coupling concepts provide reliable results only for one-dimensional  flows (parallel or perpendicular to the fluid-porous interface). Averaging techniques is a powerful mathematical tool to derive such coupling conditions. The main objectives of the project are (i) to study the applicability of different averaging theories for the development of advanced coupling concepts, (ii) to derive new interface conditions valid for arbitrary flows to the fluid-porous interface using the most suitable averaging technique, (iii) to validate the derived interface conditions, and (iv) to develop robust and efficient numerical methods for coupled  flow problems with new interface conditions.


In the first step, we demonstrated that the most commonly used interface conditions for coupled single-phase porous-medium and free-flow systems (conservation of mass, balance of normal forces, the Beavers-Joseph condition) are unsuitable for arbitrary flows to the fluid-porous interface. For the development of generalised interface conditions, we analysed strengths and limitations of different averaging techniques: homogenisation, volume averaging, thermodynamically constrained averaging theory (TCAT). For single-phase systems, the theory of homogenisation with two-scale asymptotic expansions and boundary layers was found to be the best choice, while for two-phase systems a combination of TCAT and vertical averaging is the most suitable averaging approach.

In the second step, we rigorously derived new, generalised interface conditions for arbitrary flow directions in coupled single-phase flow systems. In this case, the free flow is described by the Stokes equations, while single-phase Darcy's law is applied in the porous medium. With the newly derived coupling conditions we recovered the classical mass balance across the fluid-porous interface, obtained an extension to the balance of normal forces and a variation of the Beavers-Joseph interface condition. These generalised coupling conditions are derived using the theory of homogenisation and boundary layers, which allows to compute all the effective coeffcients appearing in the interface conditions numerically based on the pore geometry and independently of the flow direction. Appropriate error estimates between the effective and the pore-scale solutions for the velocity and pressure are obtained. 

In the third step, we validated the newly derived coupling conditions numerically via comparison of the pore-scale resolved models and the macroscale simulation results. For the model validation, we studied different porous media (isotropic, orthotropic, anisotropic), different shapes of solid inclusions and different flow scenarios. In all cases, the macroscale numerical simulations are in good agreement with the pore-scale simulations, that is not the case for the coupled models with the classical interface conditions. Even for parallel flows to the interface the new coupling conditions are more accurate than the classical ones.

In the fourth step, we proved the well-posedness of the Stokes-Darcy problem with new interface conditions. This is the basis for the development of the effcient domain decomposition method, which is currently work in progress.

Future Work

Computable models with interface conditions for arbitrary flows in two-phase coupled systems are still an open question. A general model formulation for a complex interface in coupled two-phase flow systems is theoretically derived. This model contains several unknown coefficients still to be determined. Moreover, it needs to be coupled to the free-flow model and the porous- medium model. This general model will be studied and a hierarchy of computable models of different complexities will be produced and validated. Efficient and robust numerical methods for new coupled model formulations will be developed and analysed.

For further information please constact

This image shows Iryna Rybak

Iryna Rybak

PD Dr.

Principal Investigator, Research Project A03

To the top of the page