Coupling of Porous Media Flow with Pipe Flow

Tez Türü: Doktora

Tezin Yürütüldüğü Kurum: Universitaet Stuttgart, Civil and Environmental, Department of Hydromechanics and Modelling of Hydrosystems, Almanya

Tez Danışmanı: Rainer Helmig

Tezin Onay Tarihi: 2010

Tezin Dili: İngilizce

Desteklendiği Program: Diğer

Özet:

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 macropores may trigger landslides. • Polymer electrolyte membrane fuel cells: The supply of reactive gases through freeflow 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 mentioned above. 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.