sorptionWallFunction

Description

The sorptionWallFunction is a boundary condition that provides a wall boundary condition to specify scalar/concentration gradient for turbulent and laminar flows.

The governing equation of the boundary condition is:

$$\nabla C = \frac{C^* - C_p}{\Delta_y} = \frac{F}{a \Delta_y}$$

with:

$$C^* = \frac{C_{surf}}{K}$$

and with the mass-transfer coefficient is calculated for turbulent flows:

$$a = \frac{C_\mu^{0.25} k_p^{0.5}}{y^+_{blended}}$$

or for laminar-flow and molecular-diffusion-only states:

$$a = \frac{D_m}{y_1}$$

where:

Property	Description
$\nabla C$	Gradient of concentration
$C^*$	Wall-adjacent concentration
$C_p$	Near-wall cell concentration
$\Delta_y$	First-cell centre wall distance
$F$	Flux of concentration
$a$	Mass-transfer coefficient
$C_{surf}$	Wall-surface concentration
$K$	Adsorption or absorption/permeation coefficient
$C_\mu$	Empirical model coefficient
$k_p$	Turbulent kinetic energy in near-wall cell
$y^+_{blended}$	Non-dimensional blended near-wall cell height
$D_m$	Molecular-diffusion coefficient
$y_1$	First-cell centre wall distance

References

Standard model for exponential blending (tag:FDC):

Foat, T., Drodge, J., Charleson, A., Whatmore, B.,
Pownall, S., Glover, P., ... & Marr, A. (2022).
Predicting vapour transport from semi-volatile organic
compounds concealed within permeable packaging.
International Journal of Heat and Mass Transfer, 183, 122012.
DOI:10.1016/j.ijheatmasstransfer.2021.122012

Standard model for stepwise blending (tag:F):

Foat, T. (2021).
Modelling vapour transport in indoor environments for
improved detection of explosives using dogs.
Doctoral dissertation. University of Southampton.
URI:http://eprints.soton.ac.uk/id/eprint/456709

Usage

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

Boundary file

<patchName>
{
    type            patch;
    ...
}

Field file

<patchName>
{
    // Mandatory entries
    type            compressible::sorptionWallFunction;
    Sc              <scalar>;
    Sct             <scalar>;
    kAbs            <PatchFunction1<scalar>>;

    // Optional entries
    laminar         <bool>;
    D               <scalar>;
    kName           <word>;
    nuName          <word>;

    // Inherited entries
    Cmu             <scalar>;
    kappa           <scalar>;
    E               <scalar>;
    blending        <word>;
    ...
}

where:

Property	Description	Type	Required	Default
type	Type name: compressible::sorptionWallFunction	word	yes	-
Sc	Schmidt number	scalar	yes	-
Sct	Turbulent Schmidt number	scalar	yes	-
kAbs	Adsorption or absorption/permeation coefficient	PatchFunction1<scalar>	yes	-
laminar	Flag to calculate mass-transfer coefficient under the laminar-flow or -diffusion-only states	bool	no	false
kName	Name of operand turbulent kinetic energy field	word	no	k
nuName	Name of operand kinematic viscosity field	word	no	nu

The inherited entries are elaborated in:

• fixedGradientFvPatchField.H
• wallFunctionCoefficients.H
• wallFunctionBlenders.H
• PatchFunction1.H

Further information

Tutorial:

• N/A

Source code:

• sorptionWallFunction

API:

• Foam::sorptionWallFunctionFvPatchScalarField

History: Introduced in version v2212