Reactive Transport Solver and its Future Applications

Reactive transport is an essential mechanism in various applications, including fuel cells, groundwater contamination, and enhanced oil recovery. As a first step towards reactive transport, GeoDict 2025 introduces the command "Transport Concentration Field" within AddiDict, enhancing the transient simulation of solute concentration fields driven by advection and diffusion. Unlike the existing "Track Particles & Molecules" feature, this new command employs a continuum-mechanical approach, focusing on the concentration field as the primary variable rather than tracking individual particles. This enhancement allows users to model the molar concentration of solutes within a solvent, capturing both the transport due to solvent motion (advection) and the diffusion-driven movement from high to low concentration regions. The solution algorithm was integrated into the LIR solver, and the flow field required for advection can be computed using LIR, EJ, or SimpleFFT solvers. Users have the flexibility to apply either or both transport mechanisms as needed.

Key features of "Transport Concentration Field" include stability without artifacts or oscillations, automatic time stepping for improved efficiency, minimal numerical dispersion ensuring precise solute transport, bound preservation maintaining non-negativity of concentrations, and local mass conservation. The solver accommodates the full range of Péclet numbers, from pure diffusion (Pe = 0) to pure advection (Pe = ∞), thus enabling all transport regimes. Additionally, the transport algorithm is fully compatible with adaptive grids that stem from the flow computation with the LIR solver.

Verification benchmarks are presented, in which discrete solutions are compared against analytical solutions for both advection and diffusion, demonstrating the solver’s reliability. Various breakthrough simulations of solute transport through diverse porous media are presented, in particular the simulation of a proton exchange membrane (PEM) fuel cell. This simulation models the reaction kinetics of oxygen reduction in the catalyst layer assuming constant temperature and pressure.

Finally, we outline our plans for GeoDict 2026, which will incorporate support for multiple species, complex aquatic kinetic reactions, and mineral dissolution and precipitation, further enhancing GeoDict's ability to simulate complex reactive transport processes.