Moving_Boundary

Syntax

Bc No_Coverage_Flux For Mass_Balance [{of} SpeciesName | {in} MaterialPhaseName | {ls} {a | b | c}] {@ | at | for | on | over} Mesh Extent Name [Touching TouchingMeshExtent | Opposing OpposingMeshExtent] = Moving_Boundary [Using Data Specification Data Spec Name]

Summary

Moving boundary condition, valid for Lagrangian mesh motion in non-relative flux form or relative flux form.

Description

Applies the following boundary flux

\int q \mathbf{\hat{u}} \cdot \mathbf{n} dS,

where \hat{u} is the mesh velocity and where the integrated scalar q depends on the equation. If we consider the gas phase POROUS_ENTHALPY equation with a transported enthalpy = porous, then q = \phi \rho_g h_g. Similarly, for the gas phase MASS_BALANCE equation, q = \phi \rho_g is the bulk mass density.

If we consider the gas phase MASS_BALANCE equation, with a gas phase porous velocity relative to the moving solid phase, then physically this boundary condition is derived from applying a no flux condition at moving boundary i.e.,

\mathbf{u}_g \cdot \mathbf{n} = \phi \mathbf{\hat{u}} \cdot \mathbf{n}.

In the Lagrangian setting, this flux is required to impose a no flux condition at the moving boundary with both the non-relative form (default) and relative form of the advection term. When using the relative form, typically a do-nothing condition would be sufficient to impose no flux; however, to simplify general ALE mesh motion we automatically provide the mesh motion flux on boundaries for blocks that have mesh motion. Consequently, to impose a zero flux, this term is needed for cancellation.

Parameter

Value

Default

{of}

{of | species | subindex}

–

SpeciesName

string

–

{in}

{in | material_phase}

–

MaterialPhaseName

string

–

{ls}

{levelset_phase | ls}

–

Mesh Extent Name

string

–

TouchingMeshExtent

string

–

OpposingMeshExtent

string

–

Data Spec Name

string

–