The pressurePermeableAlphaInletOutletVelocity is a velocity inlet/outlet boundary condition that can be applied to velocity boundaries for multiphase flows when the pressure boundary condition is specified.

In this condition , an open condition is applied when alpha is under a user-defined alphaMin value and a wall condition is applied when alpha is larger than the alphaMin.

This boundary condition can be used in conjunction with prghPermeableAlphaTotalPressure for the p_rgh variable.


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

Boundary file

    type            patch;

Field file

    // Mandatory entries
    type            pressurePermeableAlphaInletOutletVelocity;

    // Optional entries
    phi             <word>;
    rho             <word>;
    alpha           <word>;
    alphaMin        <scalar>;

    // Inherited entries;


Property Description Type Required Default
type Type name: pressurePermeableAlphaInletOutletVelocity word yes -
phi Name of flux field word no phi
rho Name of density field word no rho
alpha Name of the mixture VOF field word no none
alphaMin Minimum alpha value to outlet blockage scalar no 1.0

The inherited entries are elaborated in:

Further information


  • N/A

Source code:



  • Introduced in version v2106