Accounting for adsorption and desorption in lattice Boltzmann simulations

TL;DR

This paper introduces a Lattice-Boltzmann simulation method that incorporates adsorption and desorption processes, enabling more accurate modeling of tracer dynamics in complex porous media.

Contribution

It develops a novel Lattice-Boltzmann scheme with a modified moment propagation algorithm to account for surface adsorption and desorption effects.

Findings

Validated against exact diffusion results

Demonstrated impact on diffusion coefficients in porous media

Enhanced modeling of tracer-surface interactions

Abstract

We report a Lattice-Boltzmann scheme that accounts for adsorption and desorption in the calculation of mesoscale dynamical properties of tracers in media of arbitrary complexity. Lattice Boltzmann simulations made it possible to solve numerically the coupled Navier-Stokes equations of fluid dynamics and Nernst-Planck equations of electrokinetics in complex, heterogeneous media. Associated to the moment propagation scheme, it became possible to extract the effective diffusion and dispersion coefficients of tracers, or solutes, of any charge, e.g. in porous media. Nevertheless, the dynamical properties of tracers depend on the tracer-surface affinity, which is not purely electrostatic, but also includes a species-specific contribution. In order to capture this important feature, we introduce specific adsorption and desorption processes in a Lattice-Boltzmann scheme through a modified moment propagation algorithm, in which tracers may adsorb and desorb from surfaces through kinetic reaction rates. The method is validated on exact results for pure diffusion and diffusion-advection in Poiseuille flows in a simple geometry. We finally illustrate the importance of taking such processes into account on the time-dependent diffusion coefficient in a more complex porous medium.