Main ContribExamples/OscillatingFixedValue

From OpenFOAMWiki

Searching the tutorials I couldn't find an example of how to use this type of boundary condition, so I've created a very small and simple tutorial. Basically, the setup requires the definition of 4 parameters:

       type oscillatingFixedValue;
       amplitude       0.5;
       frequency       0.2;
       refValue        uniform (1 0 0);

The above setup enables to specify a velocity boundary condition for an entire patch that varies in time as:

   1+amplitude\cdot\sin\left(2\pi\cdot frequency\cdot t\right)

Unsteady Velocity Field

Sample OpenFOAM case - it applies to Valid versions: OF version 15.png

Update - it applies to Valid versions: OF Version 21.png

As from OpenFOAM 2.1.x, the dictionary for this boundary condition should read as

       type          oscillatingFixedValue;
       value         uniform 0;    // Initialization value
       refValue      uniform refV;    // Reference value for oscillation
       offset        offset;           // Oscillation mean value offset
       amplitude      constant Amp; // Amplitude of oscillation
       frequency      constant freq; // frequency

for a given scalar field. If applied to vector field, value, offset and refValue should be modified accordingly. This dictionary specifies an oscillating boundary condition of a given scalar, for an entire patch, as:

    \textrm{\textit{refV}} \cdot \left( 1.0 + \textrm{\textit{Amp}} \cdot \sin \left(2\pi\cdot \textrm{\textit{freq}}\cdot t\right)\right) + \textrm{\textit{offset}}