The blendingFactor function object computes and stores the blending coefficient employed by blended divergence schemes, giving an indicator as to which of the schemes is active across the domain.

Blended schemes combine contributions from two schemes, i.e. \(\phi_1\) and \(\phi_2\), using a weight field, i.e. \(w\), such that the effective scheme value, i.e. \(\phi_\eff\), is computed as follows:

\[\phi_\eff = w \phi_1 + (1 - w) \phi_2\]

It follows that when \(w = 1\), the scheme reduces to \(\phi_\eff = \phi_1\); similarly, when \(w = 0\), the scheme reduces to \(\phi_\eff = \phi_2\).

The weight field, i.e. \(w\), is surface field and converted to a volume field for easier post-processing by setting the cell value to one minus the minimum of the face values:

\[w_c = 1 - \min_{\forall i \in \mathrm{faces}}\left(w_{f,i}\right)\]

This conversion leads to blending indicator field whose values mean:

0   =  scheme 0
1   =  scheme 1
0-1 =  a blend between scheme 0 and scheme 1


Operand Type Location
input - -
output file dat $FOAM_CASE/postProcessing/<FO>/<time>/<file>
output field volScalarField $FOAM_CASE/<time>/<outField>


Example of the blendingFactor function object by using functions sub-dictionary in system/controlDict file:

    // Mandatory entries (unmodifiable)
    type            blendingFactor;
    libs            (fieldFunctionObjects);

    // Mandatory (inherited) entry (runtime modifiable)
    field           <field>;

    // Optional entries (runtime modifiable)
    phi             phi;
    tolerance       0.001;

    // Optional (inherited) entries
    result          <fieldResult>;
    region          region0;
    enabled         true;
    log             true;
    timeStart       0;
    timeEnd         1000;
    executeControl  timeStep;
    executeInterval 1;
    writeControl    timeStep;
    writeInterval   1;

where the entries mean:

Property Description Type Required Default
type Type name: blendingFactor word yes -
libs Library name: fieldFunctionObjects word yes -
field Name of the operand field word yes -
phi Name of flux field word no phi
tolerance Tolerance for number of blended cells scalar no 0.001

The inherited entries are elaborated in:

Usage by the postProcess utility is not available.

Notes on entries

The field and phi entries are used to construct the scheme name to lookup from the fvSchemes dictionary, as:


The tolerance entry is used as a threshold when computing the number of cells identified as using each scheme. The tolerance entry must be in the range 0 to 1, excluding the endpoints.

Stored properties


The blending factor is stored on the mesh database, using the default name:


The name can be overridden by using the result entry.

Further information



Source code: