advective

Description

The advective is a general boundary condition to simulate non-reflecting advective outflow condition, based on solving the material derivative of the given field on the boundary.

The material derivative is solved for a given field:

$$\frac{D \phi}{D t} \approx \frac{\partial \phi}{\partial t} + U_n \cdot \frac{\partial \phi}{\partial \mathbf{n}} = 0$$

where:

Property	Description
$\phi$	Field
$U_n$	Advection velocity component normal to boundary
$\mathbf{n}$	Outward-pointing unit boundary-normal vector

Usage

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

Boundary file

<patchName>
{
    type            patch;
    ...
}

Field file

<patchName>
{
    // Mandatory entries
    type            advective;

    // Optional entries
    phi             <word>;
    rho             <word>;
    lInf            <scalar>;

    // Conditional entries

        // when lInf is given
        fieldInf    <Type>;

    // Inherited entries
    ...
}

where:

Property	Description	Type	Required	Default
type	Type name: advective	word	yes	-
phi	Name of the flux transporting the field	word	no	phi
rho	Name of the density field used to normalise the mass flux	word	no	rho
lInf	Relaxation length-scale	scalar	no	-GREAT
fieldInf	Field value of the far-field	Type	no	Zero

The inherited entries are elaborated in:

• mixedFvPatchFields.H

• The standard time schemes (backward, Euler, CrankNicolson, localEuler) are supported.
• The relaxation length-scale lInf and the far-field value fieldInf are to optionally relax the value at the boundary to a specified far-field value.
• If lInf is specified, fieldInf will be required.
• rho is only required in the case of a mass-based flux.
• The advection velocity is assumed to be normal to the boundary.

Further information

Tutorial:

• planeChannel

Source code:

• advective

API:

• Foam::advectiveFvPatchField

History: Introduced in version 1.5