The flowRateInletVelocity is a velocity boundary condition that either corrects the extrapolated velocity or creates a uniform velocity field normal to the patch adjusted to match the specified flow rate. The condition is a wrapper around the fixedValue condition.


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

Boundary file

    type            patch;

Field file

    // Mandatory entries
    type                flowRateInletVelocity;

    // Conditional entries

        // Option-1
        volumetricFlowRate  <Function1<scalar>>;

        // Option-2
        massFlowRate        <Function1<scalar>>;

    // Optional entries
    rho                 <word>;
    rhoInlet            <scalar>;
    extrapolateProfile  <bool>;

    // Inherited entries


Property Description Type Required Default
type Type name: flowRateInletVelocity word yes -
volumetricFlowRate Volumetric flow rate Function1<scalar> choice -
massFlowRate Mass flow rate Function1<scalar> choice -
rho Name of density field word no rho
rhoInlet Density initialisation value scalar no -VGREAT
extrapolateProfile Flag to extrapolate the velocity profile from the interior bool no false

The inherited entries are elaborated in:

  • fixedValueFvPatchFields.H
  • Function1.H

  • For a mass-based flux input:
    • The flow rate should be provided in [kg/s].
    • If rho is none the flow rate is in [m^3/s].
    • Otherwise rho should correspond to the name of the density field
    • If the density field cannot be found in the database, the user must specify the inlet density using the rhoInlet entry.
  • For a volumetric-based flux:
    • The flow rate is in [m^3/s].

A uniform plug flow is set by default. To set the profile according to the downstream cells:

extrapolateProfile  yes;

To convert from a mass flow rate to a volumetric flow rate:

rho                 rho;

To convert from a mass flow rate to a volumetric flow rate for incompressible flows:

rhoInlet            1.0;



Further information


Source code:



  • Introduced in version 1.5