(350b) Computer Simulation of Flow and Transport Processes in Deformable Porous Media

Understanding how deformation affects flow and transport processes has a fundamental scientific importance, and has attracted considerable attention, both experimentally and computationally. We study the changes in the porosity, permeability and conductivity of a porous medium, when it is under mechanical compaction. Random and regular (Faced Center Cubic (FCC) and Body Centered Cubic (BCC)) packings of deformable spherical particles are used as models of the porous materials. For random packing generation, unequal spherical particles are randomly placed in a cube with overlapping states. Subsequently, the overlapping state is transformed to an isotropic and non-overlap packing by a Monte Carlo simulation model. Hertz contact theory is used to model mechanical characteristics of the packings when they are under a uniaxial compression. An external loading is applied to the packing incrementally, and at each time step the new configuration of the pore space is determined, and the permeability of the packing is computed by the lattice Boltzmann method (LBM) with nine velocities (D3Q19). The porosity and fluid permeability are computed as a function of the external loading.

   Effective diffusivities and conductivities of packings are computed by a Monte Carlo random-walk technique. In this method a walker is randomly placed in the pore space that executes a random walk (Brownian motion) in the porous medium.  The random walk simulation is carried out for a large number of walkers. The effective diffusivity and conductivity are calculated based on the mean-square displacement of the walkers. Moreover, Archie’s cementation exponents are computed based on random walk simulation and compared for the packings before and after the compression. Thus, a change in the effective diffusivity, conductivity and Archie’s cementation exponents of packings as a result of uniaxial compression has been studied.