The advective is a general boundary condition to simulate non-reflecting advective outflow condition, based on solving the material derivative of the given field on the boundary.


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

Boundary file

    type            patch;

Field file

    // Mandatory entries
    type            advective;

    // Optional entries
    phi             <word>;
    rho             <word>;
    lInf            <scalar>;

    // Conditional entries

        // when lInf is given
        fieldInf    <Type>;

    // Inherited entries


Property Description Type Required Default
type Type name: advective word yes -
phi Name of the flux transporting the field word no phi
rho Name of the density field used to normalise the mass flux word no rho
lInf Relaxation length-scale scalar no -GREAT
fieldInf Field value of the far-field Type no Zero

The inherited entries are elaborated in:

  • mixedFvPatchFields.H

  • The standard (backward, Euler, CrankNicolson, localEuler) time schemes are supported.
  • The relaxation length-scale lInf and the far-field value fieldInf are to optionally relax the value at the boundary to a specified far-field value.
  • If lInf is specified, fieldInf will be required.
  • rho is only required in the case of a mass-based flux.
  • The advection velocity is assumed to be normal to the boundary.


The material derivative is solved for the given field:

\[\frac{D \phi}{D t} \approx \frac{\partial \phi}{\partial t} + U_n \cdot \frac{\partial \phi}{\partial \mathbf{n}} = 0\]


Property Type
\(\phi\) Field
\(U_n\) Advection velocity component normal to boundary
\(\mathbf{n}\) Outward-pointing unit boundary-normal vector

Further information


Source code:



  • Introduced in version 1.5