# model domain command

Syntax

model domain keyword

Specify the domain boundaries and conditions. DFN fractures only exist within the domain extent.

Note

In FLAC3D, zones and structural elements are not aware of the model domain.

In PFC, walls clumps and balls must be inside of the domain and are aware of the domain boundary conditions.

condition keyword <keyword keyword>

Set the domain boundary conditions. Each domain condition applies to the two box sides that are perpendicular to the direction.

The first keyword specifies the condition for the x direction. The second for the y, and the third for the z. If only one keyword is specified, then y and z are set to the same condition as x. The default condition is the stop condition.

The following keywords can be used to specify domain conditions.

stop

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

reflect

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.

destroy

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.

periodic

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.

extent fxl fxu

Specify the locations of the sides of the domain. Each set of values applies to the lower and upper bound of that dimension of the domain. If fxl and fxu are specified alone, then the domain is a cube.