The freestream is a generic boundary condition that provides a free-stream condition. It is a mixed condition derived from the inletOutlet condition, whereby the mode of operation switches between fixed (free stream) value and zero gradient based on the sign of the flux.


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

Boundary file

    type            patch;

Field file

    // Mandatory entries
    type            freestream;

    // Conditional entries

        // Option-1
        freestreamValue        <Field<Type>>;

        // Option-2
        freestreamBC           <fvPatchField<Type>>;

    // Optional entries
    phi             <word>;

    // Inherited entries;


Property Description Type Required Default
type Type name: freestream word yes -
freestreamValue Patch value Field<Type> choice -
freestreamBC Separate boundary condition fvPatchField<Type> choice -
phi Name of flux field word no phi

The inherited entries are elaborated in:

Further information


Source code:



  • Introduced in version 1.5