activeBaffleVelocity

Description

The activeBaffleVelocity is a velocity boundary condition that simulates the opening of a baffle due to local flow conditions, by merging the behaviours of wall and cyclic conditions. The baffle joins two mesh regions, where the open fraction determines the interpolation weights applied to each cyclic- and neighbour-patch contribution.

Usage

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

Boundary file

<patchName>
{
    type            patch;
    ...
}

Field file

<patchName>
{
    // Mandatory entries
    type            activeBaffleVelocity;
    cyclicPatch     <word>;
    orientation     <label>;
    openFraction    <scalar>;
    openingTime     <scalar>;
    maxOpenFractionDelta <scalar>;

    // Optional entries
    p               <word>;

    // Inherited entries
    ...
}

where:

Property	Description	Type	Required	Default
type	Type name: activeBaffleVelocity	word	yes	-
cyclicPatch	Name of cyclic patch used when the active baffle is open	word	yes	-
orientation	Orientation (1 or -1) of the active baffle patch	label	yes	-
openFraction	Current fraction of the active baffle which is open	scalar	yes	-
openingTime	Time taken for the active baffle to open	scalar	yes	-
maxOpenFractionDelta	Maximum fractional change to the active baffle openness per time step	scalar	yes	-
p	Name of pressure field	word	no	p

The inherited entries are elaborated in:

• fixedValueFvPatchField.H

• The orientation is used to change the direction of opening without the need for reordering the patch faces.

Method

It is determined whether the baffle is opening or closing from the sign of the net force across the baffle, from which the baffle open fraction is updated using:

$$x = x_{old} + sign(F_{net})\frac{dt}{DT}$$

where:

Property	Description
$x$	Baffle open fraction [0-1]
$x_{old}$	Baffle open fraction on previous evaluation
$dt$	Simulation time step
$DT$	Time taken to open the baffle
$F_{net}$	Net force across the baffle

The open fraction is then applied to scale the patch areas.

Further information

Tutorial:

• N/A

Source code:

• activeBaffleVelocity

API:

• Foam::activeBaffleVelocityFvPatchVectorField

History: Introduced in version 1.5