Description🔗
The activePressureForceBaffleVelocity
is a velocity boundary condition to
simulate the opening or closure of a baffle due to area averaged pressure or
force delta, between both sides of the baffle. This is achieved by merging the
behaviours of wall and cyclic baffles.
Usage🔗
The condition requires entries in both the boundary
and field files.
Boundary file🔗
<patchName>
{
type patch;
...
}
Field file🔗
<patchName>
{
// Mandatory entries
type activePressureForceBaffleVelocity;
cyclicPatch <word>;
openFraction <scalar>;
openingTime <scalar>;
maxOpenFractionDelta <scalar>;
minThresholdValue <scalar>;
forceBased <bool>;
opening <bool>;
// Optional entries
p <word>;
// Inherited entries
...
}
where:
Property | Description | Type | Required | Default |
---|---|---|---|---|
type |
Type name: activePressureForceBaffleVelocity
|
word | yes | - |
cyclicPatch |
Name of cyclic patch used when the active baffle is open | word | 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 | - |
minThresholdValue |
Minimum value for the active baffle to start opening | scalar | yes | - |
forceBased |
Flag to activate force based baffle | bool | yes | - |
opening |
Flag to decide if baffle is opening or closing (1 opening, 0 closing) | bool | yes | - |
p |
Name of pressure field | word | no | p |
The inherited entries are elaborated in:
- fixedValueFvPatchFields.H
Method🔗
The baffle joins two mesh regions, where the open fraction determines the interpolation weights applied to each cyclic- and neighbour-patch contribution. This means that this is boundary condition is meant to be used in an extra wall beyond an existing cyclic patch pair.
The baffle is activated when the area weighted pressure difference between
master and slave patches is larger then minThresholdValue
.
Once the threshold is crossed, the baffle is activated and continues to open or close at a fixed rate using:
\[x = x_{old} + s \times \frac{dt}{DT}\]where:
Property | Description |
---|---|
\(x\) | Baffle open fraction [0-1] |
\(x_{old}\) | Baffle open fraction on previous evaluation |
\(s\) | Sign for orientation: 1 to open or -1 to close |
\(dt\) | Simulation time step |
\(DT\) | Time taken to open the baffle |
The open fraction is then applied to scale the patch areas.
Further information🔗
Tutorial:
Source code:
API:
History:
- Introduced in version 1.5