The Surface Reactions Interface (
) models reactions involving surface adsorbed species and species in the bulk of a reacting surface. The physics interface is typically active on a model boundary and is coupled to a mass transport physics interface active on a model domain. The Surface Reactions interface can be used together with other Chemical Species Transport interfaces, the Reacting Flow interfaces, and the Electrochemistry interfaces. Predefined expressions for the growth velocity of the reacting surface makes it easy to set up models with moving boundaries. Also see the
Theory for the Surface Reactions Interface.
The mass transfer equations account for chemical species transport by diffusion, convection, and migration due to an electric field (electrokinetic flow)—either alone or in combination. The Transport of Diluted Species Interface (
) is an enhanced version of the physics interface included with the basic COMSOL Multiphysics
license and is applicable for solutions (either fluid or solid) where the transported species have concentrations at least one order of magnitude less than the solvent. The settings for this physics interface can be chosen so as to simulate chemical species transport through diffusion (Fick’s law), convection (when coupled to fluid flow), and migration (when coupled to an electric field — electrokinetic flow).
The Transport of Diluted Species in Porous Media Interface (
) is tailored for the modeling of solute transport in porous media. The physics interface supports cases where either the solid phase substrate is exclusively immobile, or when a gas-filling medium is also assumed to be immobile.
The Transport of Concentrated Species Interface (
) is used for modeling transport within mixtures where no one component is clearly dominant. Often the concentrations of the participating species are of the same order of magnitude, and the molecular effects of respective species on each other needs to be considered. This physics interface supports transport through Fickian diffusion, a mixture-average diffusion model, and as described by the Maxwell-Stefan equations. These take into account the diffusion properties of all species with respect to each other. Convective transport and transport by migration in electric fields are also accounted for by this physics interface. Also see the
Theory for the Transport of Diluted Species Interface.
The Nernst–Planck Equations Interface (
) includes a migration term, along with convection and diffusion mass transport, together with an equation that guarantees electroneutrality. A term to describe the electric potential is also provided in the physics interface itself. Also see the
Theory for the Nernst–Planck Equations Interface.
The Reacting Flow in Porous Media, Transport of Diluted Species Interface (
) (found under the
Chemical Species Transport>Reacting Flow in Porous Media branch (
) when adding a physics interface), is a multiphysics interface treating diluted reacting mixtures transported by a porous media flow. The nonlocal coupling for the velocity field is set up automatically.
The Reacting Flow in Porous Media, Transport of Concentrated Species Interface(
) found under the
Chemical Species Transport>Reacting Flow in Porous Media branch (
) when adding a physics interface), is a multiphysics interface treating concentrated reacting mixtures transported by a porous media flow. The couplings between velocity field and mixture density are set up automatically.
