Multiphase flow and transport processes in porous media with structures on different scales are relevant for several scientific research areas as well as application realms, as e.g.
- the transport of contaminants such as pesticides or heavy metals in the vadose zone of soils leading to groundwater contamination,
- assessing the security of nuclear waste disposal sites,
- the description of sites contaminated with non-aqueous phase liquids and the monitoring of appropriate decontamination measures.
Neighbouring research fields include the use of filters or the infiltration of ink into paper. In order to successfully address these challenges one has to understand the multiphase flow processes on scales ranging from the micro- to the macroscale. Based on this understanding appropriate physical and mathematical models have to be formulated and applied deploying suitable techniques.

Within the proposed project we want to develop methods which allow a better prediction of transport in unsaturated media. Therefore we have to analyse dynamic, nonlinear two-phase flow processes on the microscale and their translation to the mesoscale. At the same time
dynamic, nonlinear two-phase flow processes on the macroscale and their upscaling will be studied. The main focus will be put on the in influence of structures of the different scales on two-phase flow processes.

This project aims on the enhancement for prediction of transport in unsaturated soils and is a cooperation of the Institute of Terrestrial Ecology from the ETH Zurich, the Institute of Hydraulic Engineering, University of Stuttgart and the Institute for Computerapplications in Civil Engineering, University of Brunswick.

This project is divided into three subprojects. To get more information about the goals of the individual project follow the links on the navigation bar.

General work plan

Identification and quantification of structures

1. Acquisition of the three-dimensional pore structure of sands by means of image analysis of synchrotron tomography data and quantification of the geometric properties of the pore space

2. Generation of artificial pore geometries

3. Determination of meso- to macroscale structures and fluid distribution applying neutron transmission measurements in heterogeneous systems containing two sand materials

Identification of the influence of structure on two-phase flow processes on the microscale

4. Numerical simulations of two-phase flow processes on the microscale with lattice-Boltzmann methods using scanned pore geometries and artificial pore geometries

5. Measurement of the fluid distributions in small samples by means of synchrotron tomography and comparison of results to 4)

6. Identification of the relevant processes for steady-state and dynamic processes (steady-state and transient) by means of a dimensional analysis as well as numerical and laboratory experiments

7. Determination of an REV on the microscale and quantification of effective parameters (intrinsic permeability, constitutive relationships) on the mesoscale as functions of parameters describing fluid properties (e.g. viscosity ratio, Capillary number, contact angle) and as well as parameters describing the pore geometry (e.g. Minkowski functionals)

Identification of the influence of structure on two-phase flow processes on the macroscale

8. Numerical simulations of two-phase flow processes in homogeneous systems (laboratory column experiments) applying the effective parameters found on the microscale

9. Numerical simulations of two-phase flow processes in heterogeneous systems on the basis of a) the laboratory experiments in heterogeneous sands and b) artifically generated random heterogeneities

10. Identification of the relevant processes for steady-state and transient processes by means of a dimensional analysis, numerical and laboratory experiments

11. Determination of an REV on the macroscale and quantification of effective constitutive relationships as functions of fluid properties (viscosity ratio) and structural information (Minkowski functionals, first and second order parameters) and the process (drainage and imbibition)

12. Extension of the constitutive relationships and/or balance equations by direction-dependence and/or dynamic term and validation of the new algorithm by comparison to laboratory experiments

13. Application of extended balance equations (dynamic Pc-Sw) in stochastical upscaling approach of the Richards equation