# domain.condition command

Syntax

domain condition sx <sy sz > (sz is 3D only)

Set the domain boundary conditions.

Note

Domains are mostly pertinent to PFC. In a FLAC3D model, only discrete fracture networks (DFNs) will be affected by the domain.

Each domain condition applies to the two box sides that are perpendicular to the direction (e.g., sx applies to the two sides that are perpendicular to the x-direction). If sx is specified alone, then this condition applies to all boundaries. Otherwise, {two strings in the order x,y in 2D; three strings in the order x,y,z in 3D} must be specified. The default condition is the stop condition.

Acceptable boundary conditions are stop, reflect, destroy and periodic.

The stop condition imposes the constraint that when the body centroid falls outside the model domain, the velocity and spin of the body are nulled. For walls, once a facet centroid falls outside the model domain, the velocity and spin are nulled, including any vertex velocities.

The reflect condition imparts the opposite sign of the velocity, and the spin is unchanged if the body centroid falls outside the model domain. The use of this condition as a contact rule is not recommended since it may induce instabilities. The reflect condition is not compatible with walls intersecting the domain.

The destroy condition deletes balls, clumps and wall facets whose individual extents (i.e., an axis-aligned bounding box that tightly encompasses the object) fall outside the model domain.

The periodic condition applies periodic boundary conditions. When the ball or clump centroid falls outside of the model domain, they are translated back to the opposite side of the model. To ensure that contacts are created as if the model was continuous, “ghost” balls and clumps are introduced. The periodic condition is not compatible with walls intersecting the domain.

CS: some accommodation of FLAC3D is probably wanted here; something that explains that this is more of a pfc thing, but it has applicability in F3D in the following manner…