The fanPressure is a pressure boundary condition to assign either a pressure inlet or outlet total pressure condition for a fan. The condition sets the static pressure from a definition of the total pressure and pressure drop as a function of volumetric flow rate across the patch.


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

Boundary file

    type            patch;

Field file

    // Mandatory entries
    type            fanPressure;
    fanCurve        <Function1<scalar>>;
    direction       <word>;

    // Optional entries
    nonDimensional  <bool>;

    // Conditional entries

      // if 'nonDimensional' is true
      rpm           <Function1<scalar>>;
      dm            <Function1<scalar>>;

    // Inherited entries;


Property Description Type Required Default
type Type name: fan word yes -
fanCurve Dataset of pressure vs flow rate Function1<scalar> yes -
direction Direction of flow through fan word yes -
nonDimensional Flag to use non-dimensional curves bool no false
rpm Fan rpm (for non-dimensional curve) Function1<scalar> conditional -
dm Fan mean diameter (for non-dimensional curve) Function1<scalar> conditional -

Options for the direction entry:

Property Description
in Into the fan
out Out of the fan

The inherited entries are elaborated in:

  • totalPressureFvPatchScalarField.H
  • Function1.H

  • For compatibility with older versions (OpenFOAM-v2006 and earlier), a missing fanCurve keyword is treated as a tableFile and makes the file keyword mandatory.


The non-dimensional flux is calculated as follows:

\[phi = \frac{4 \dot{m}}{\rho \pi^2 d_m^3 \omega}\]

The non-dimensional flux is calculated as follows:

\[\Psi = \frac{2 \Delta P}{\rho (\pi \omega d_m)}\]
Property Description
\(d_m\) Fan mean diameter [m]
\(\Delta P\) Pressure drop
\(\omega\) Rotational speed [rad/s]
\(\dot{m}\) Mass flow rate

The non-dimensional table should be given as \(\Psi = F(\phi)\).

The condition sets the static pressure at the patch \(p_p\) based on a specification of the total pressure, \(p_0\), and pressure drop, \(p_d\), specified as a function of the volumetric flow rate.

\[p_p = p_0 - p_d\]

Further information


Source code:



  • Introduced in version 1.5