The fixedMeanOutletInlet is a general boundary condition that extrapolates field to the patch using the near-cell values and adjusts the distribution to match the specified, optionally time-varying, mean value. This extrapolated field is applied as a fixedValue for outflow faces but zeroGradient is applied to inflow faces.

This boundary condition can be applied to pressure when inletOutlet is applied to the velocity so that a zeroGradient condition is applied to the pressure at inflow faces where the velocity is specified to avoid an unphysical over-specification of the set of boundary conditions.


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

Boundary file

    type            patch;

Field file

    // Mandatory entries
    type            fixedMeanOutletInlet;
    meanValue       <Function1<Type>>;

    // Optional entries
    phi             <word>;

    // Inherited entries;


Property Description Type Required Default
type Type name: fixedMeanOutletInlet word yes -
meanValue Mean value that the field is adjusted to maintain Function1<Type> yes -
phi Name of flux field word no phi

The inherited entries are elaborated in:

  • outletInletFvPatchFields.H
  • Function1.H



Further information


  • N/A

Source code:



  • Introduced in version v1806