The prghPermeableAlphaTotalPressure is a is a mixed boundary condition for the p_rgh variable in multiphase flows.

It switches between an open boundary using the prghTotalPressure boundary condition and a wall condition using the fixedFluxPressure boundary condition.

In the prghPermeableAlphaTotalPressure, 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 pressurePermeableAlphaInletOutletVelocity for the U variable.


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

Boundary file

    type            patch;

Field file

    // Mandatory entries
    type            prghPermeableAlphaTotalPressure;
    p               <PatchFunction1<scalar>>;

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

    // Inherited entries;


Property Description Type Required Default
type Type name: prghPermeableAlphaTotalPressure word yes -
p Total pressure PatchFunction1<scalar> yes -
phi Name of flux field word no phi
rho Name of density field word no rho
U Name of velocity field word no U
alpha Name of mixture field word no alpha
alphaMin Minimum value of alpha scalar no 1

The inherited entries are elaborated in:

Further information


Source code:



  • Introduced in version v2106