diffusivity matrix is an Q-by-Q symmetric matrix, where the diagonal components are 1. Enter values for the upper triangular components, Dij, which respectively describes the interdiffusion between species number i and number j. The numbering of the species corresponds to the order, from top to bottom, used for all the input fields for species properties (see for example the molar mass fields in the Density section).

Diffusion Coefficient

Using a Fick’s law diffusion model, the diffusion is by default assumed to be isotropic and governed by a Diffusion coefficient DFi (SI unit: m2/s) for each of the species. To allow for a general representation, it is also possible to use diffusion matrices (diagonal, symmetric or anisotropic).

Multicomponent Thermal Diffusion

To model thermal diffusion, prescribe the thermal diffusion coefficients DTi

(SI unit: m2/s), by entering one thermal diffusion coefficient for each species in the corresponding field. In a multicomponent mixture, the sum of the thermal diffusion coefficients is zero. The default value for all thermal diffusion coefficients is 0.

M I G R A T I O N I N E L E C T R I C F I E L D

This section is available when the Migration in electric field check box is selected on the

Transport of Concentrated Species Settings window.

Enter values or expressions for the Mobility variables um,w1 and um,w2

(SI unit: s·mol/ kg) and Charge number variables zw1 and zw2 (unitless).

Reactions

In order to account for consumption or production of species due to reactions, the Reactions node adds rate expressions to the right hand side of the species transport

equations.

D O M A I N S E L E C T I O N

From the Selection list, choose the domains to use the rate expressions defined in the

Reactions feature node.

R E A C T I O N S

Add a rate expression, Ri (SI unit: kg/(m3·s)), for all individual species present except the one computed from the mass constrain (see Species). Enter a value or expression in the field of the corresponding species.

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