semiPermeableBaffleMassFraction

Description

The semiPermeableBaffleMassFraction is a boundary condition that provides a mass-fraction boundary condition for a semi-permeable baffle.

This condition models a baffle which is permeable to a some species and impermeable to others. It must be used in conjunction with the corresponding velocity condition, semiPermeableBaffleVelocity.

The mass flux of a species is calculated as a coefficient multiplied by the difference in mass fraction across the baffle.

$$\phi_{Yi} = c A (Y_i - Y_{i,n})$$

where:

Property	Description
$\phi_{Yi}$	Flux of the permeable species [kg/s]
$c$	Transfer coefficient [kg/m^2/s]
$A$	Patch face area [m^2]
$Y_i$	Mass fraction on the patch [-]
$Y_{i,n}$	Mass fraction on the neighbour patch [-]

A species that the baffle is permeable to will, therefore, have a coefficient greater than zero, whilst a species that does not transfer will have a coefficient equal to zero.

This condition calculates the species flux. The fluxes are summed up by the velocity condition to generate the net mass transfer across the baffle. This mass-fraction condition then generates a corrective diffusive flux to ensure that the correct amounts of the permeable species are transferred.

Usage

The condition requires entries in both the boundary and field files.

Boundary file

<patchName>
{
    type            patch;
    ...
}

Field file

<patchName>
{
    // Mandatory entries
    type            semiPermeableBaffleMassFraction;

    // Optional entries
    c               <scalar>;
    phi             <word>;

    // Inherited entries
    ...
}

where:

Property	Description	Type	Required	Default
type	Type name: semiPermeableBaffleMassFraction	word	yes	-
c	Transfer coefficient	scalar	no	0
phi	Name of flux field	word	no	phi

The inherited entries are elaborated in:

• mappedPatchBase.H
• mixedFvPatchFields.H

Further information

Tutorial:

• N/A

Source code:

• semiPermeableBaffleMassFraction

API:

• Foam::semiPermeableBaffleMassFractionFvPatchScalarField

History: Introduced in version v2206