Eigenverlag des Instituts für Wasserbau, Stuttgart, 2011
Many flow problems in environmental, technical and biological systems are characterized
by a distinct interaction between a flow region in porous medium and a free flow region in
quasi-one-dimensional hollow structures. Examples for such systems are:
Mines: Methane released from unmined coal seams migrates through the porous
rocks, but also through tunnels and shafts in the mine.
Landslides: A sudden water infiltration through macro-pores may trigger landslides.
Polymer electrolyte membrane fuel cells: The supply of reactive gases through free-flow
channels into the porous diffusion layers interacts strongly with the evacuation
process of the water, which is formed at the cathode reaction layer and flows from the
porous diffusion layers into the free-flow channels .
Cancer therapy: Therapeutic agents are delivered via the blood vessels into the tissue,
targeting the tumor cells.
The goal of this study is to introduce new coupling strategies and to develop coupled numerical
models which can form a basis for further studies modeling the complex systems
In this study, different model concepts based on a dual-continuum strategy for the simulation
of coupled porous media flow with lower-dimensional pipe flow are further developed
and tested. For the numerical implementation a special grid called 1D pipe network grid in
a 3D porous grid is developed.
The dual-continuum concept is extended for coupling multi-phase porous media flow with
lower-dimensional single-phase pipe flow. The complexity of the considered flow regimes
is increased gradually. Examples are given for a coupled single-phase incompressible and
compressible flow in both porous media and pipe flow domains. The single-phase coupling
strategy is tested by comparing the results with results of the experiment done in controlled
laboratory conditions. Furthermore, the coupling of single-phase pipe flow with a multiphase
flow based on Richards equation for the unsaturated soil zone is modeled, where the
important role of capillary effects for the mass exchange rate between the two continua can
be illustrated. The next model introduces a concept for a two-phase porous media flow coupled
with a single-phase (gas) pipe flow problem, which reveals that the mobility exchange
term can be decisive for the mass exchange rate. The final model presents a concept for
coupling two-phase two-component porous media flow with single-phase two-component
pipe flow. This model is able to simulate more complicated transport systems by accounting
not only for the mobility exchange term but also for the concentrations of the exchanged
components between the continua. It is shown that the concentration of the components in
each continua play a significant role for the compositional ratio of the exchanged mass.