The surfaceDisplacement is a boundary condition that provides displacement fixed by projection onto triSurface. Use in a displacementMotionSolver as a boundary condition on a pointDisplacement field.


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

Boundary file

    type            patch;

Field file

    // Mandatory entries
    type            surfaceDisplacement;
    velocity        <vector>;
    geometry        <dict>;
    projectMode     <word>;
    projectDirection  <vector>;

    // Optional entries
    wedgePlane      <label>;
    frozenPointsZone  <word>;

    // Inherited entries


Property Description Type Required Default
type Type name: surfaceDisplacement word yes -
velocity Maximum velocity vector yes -
geometry Dictionary with searchableSurfaces. (usually triSurfaceMeshes in constant/triSurface) word yes -
projectMode Projection mode word yes -
projectDirection Projection direction vector yes -
wedgePlane -1 or component to knock out of intersection normal label no -1
frozenPointsZone Empty or name of pointZone containing points that do not move word no null

Options for the projectMode entry:

Property Description
POINTNORMAL Intersection with point normal
FIXEDNORMAL Intersection with fixed vector

The inherited entries are elaborated in:

  • fixedValuePointPatchField.H

  • This displacement is then clipped with the specified velocity*deltaT.
  • Optionally (intersection only) removes a component (wedgePlane) to stay in 2D.

Further information


Source code:



  • Introduced in version 1.6