Numerical hydrodynamic and mass transport modelling accross a pyrochlore surface using OpenFOAM

The study and understanding of material dissolution plays and important role in environmental sciences, e.g. in the study of pipeline corrosion, reservoir development or nuclear waste storage. Commonly laboratory based experiments or meso-scale numerical simulations are carried out to verify the resistivity of a material with regard to dissolution. However, it is challenging to directly determine the interaction between fluid movement and mass transport on the microscale. In order to overcome this difficulty we use a 3D numerical hydrodynamic continuum model by which the fluid flow and the mass transport over a pyrochlore surface are simulated. Using the finite volume method implemented in the open-source software package OpenFOAM, we investigated the hydrodynamic flow over three pyrochlore surfaces of varying surface roughness under steady-state conditions. The steady-state flow field is further used to derive the influence on the mass transport at the microscale. The results of the hydrodynamic simulations show the horizontal stratification of the laminar flow. We observe the development of cavity flows in the surface depressions. Likewise the transport simulation show the influenve of the cavity flows, which are trapping saturated fluid close to the surface. We see a preferred transport across the surface, with little mixing into the surface depressions and the development of a diffusion boundary layer. These effects become more pronounced with increasing surface roughness.