The SRFFreestreamVelocity is a boundary condition that provides freestream velocity condition to be used in conjunction with the single rotating frame (SRF) model (see: SRFModel class).

Given the free stream velocity in the absolute frame, the condition applies the appropriate rotation transformation in time and space to determine the local velocity using:

\[\u_p = cos(\theta) \u_{Inf} + sin(\theta) (n \times \u_{Inf}) - \u_{p,srf}\]


Property Description
\(\u_p\) Patch velocity [m/s]
\(\u_{Inf}\) Free stream velocity in the absolute frame [m/s]
\(\theta\) Swept angle [rad]
\(n\) Axis direction of the SRF
\(\u_{p,srf}\) SRF velocity of the patch [m/s]


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

Boundary file

    type            patch;

Field file

    // Mandatory entries
    type            SRFFreestreamVelocity;
    UInf            <vector>;

    // Optional entries
    relative        <bool>;

    // Inherited entries;


Property Description Type Required Default
type Type name: SRFFreestreamVelocity word yes -
UInf Velocity of the free stream in the absolute frame vector yes -
relative Flag to decide if the supplied inlet value relative to the SRF bool no false

The inherited entries are elaborated in:

  • inletOutletFvPatchFields.H

Further information


Source code:



  • Introduced in version 2.0.0