The activePressureForceBaffleVelocity is a velocity boundary condition that simulates 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.

The baffle joins two mesh regions, where the open fraction determines the interpolation weights applied to each cyclic- and neighbour-patch contribution. This 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

\[x = x_{old} + s \, \frac{\Delta t}{T}\]


Property Description
\(x\) Baffle open fraction [0-1]
\(x_{old}\) Baffle open fraction on previous evaluation [0-1]
\(\Delta t\) Simulation time step [s]
\(T\) Time taken to open the baffle [s]
\(s\) Sign for orientation: 1 to open or -1 to close

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


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

Boundary file

    type            wall;

Field file

    // Mandatory entries
    type                  activePressureForceBaffleVelocity;
    cyclicPatch           <word>;
    orientation           <label>;
    openFraction          <scalar>;
    openingTime           <scalar>;
    maxOpenFractionDelta  <scalar>;
    minThresholdValue     <scalar>;
    forceBased            <bool>;
    opening               <bool>;

    // Optional entries
    p                     <word>;

    // Inherited entries


Property Description Type Required Default
type Type name: activeBaffleVelocity word yes -
cyclicPatch Name of cyclic patch word yes -
orientation Flag to switch flow direction, either 1 or -1 label yes -
openFraction Current open fraction of patch [0-1] scalar yes -
openingTime Time taken to open the baffle scalar yes -
maxOpenFractionDelta Max open fraction change per timestep scalar yes -
minThresholdValue Min absolute pressure or force difference for activation scalar yes -
forceBased Force (true) or pressure-based (false) activation bool yes -
opening Baffle is opening (true) or closing (false) bool yes -
p Name of pressure field word no p

The inherited entries are elaborated in:

  • fixedValueFvPatchField.H

Further information


Source code:



  • Introduced in version 2.0.0