Multiphase Fluid Handling in Absorbing Materials- Simulating Porous Media Using OpenFoam

Abstract

Absorption takes place in many fields and applications, for instance, water absorption of soil and wicking of textiles. Computational models have been developed for many applications such as groundwater absorption and absorption of absorbents. The aim of this thesis is to establish computational models for absorbing materials and study absorption through modelling and experiments. The understanding of absorption is based on theories that two-phase fluids interact with a porous medium, which absorbing materials are regarded as. The modelling of this phenomenon can deepen the understanding and aid in further development of absorbing materials. The experimental data can be understood by the help of modelling and the data can validate the model. In CFD simulation, the parameters of porous media including porosity, permeability and air entry pressure are included in the equations, stressing the importance of the experiments. There are existing capillary pressure models empirically developed in order to include the capillary pressure inside the porous media, and relative permeability models developed to introduce permeability in the porous media. OpenFoam is the open-source software that is used as a main simulation tool to model absorption in the work. Absorption is modelled in macro scale which represents the general performances of absorbing materials. The initial case proved that the capillary forces were the driving force for the fluid flow inside the material. To further investigate absorbing materials, the effects of gravity and anisotropy were modelled. The capillary pressure models and relative permeability models were assessed to examine their performances in order to select corresponding models or modify the models based on selected models in different situations. Since boundary conditions are vital to simulations, a study of boundary conditions is done depending on different occasions of absorption in materials. The permeability measurement and porosity measurement were performed to provide the model which models capillary forces with some input data. The fluid transport in experiments and simulations were compared. The fluid fronts and the saturation distributions show similar behaviours except the time which is longer in the simulations. Further research and development should be performed to improve the model.