The domain is an axis-aligned bounding box. Model components that utilize contact detection exist within the domain. Model components that do not exist in the model domain include zones, gridpoints, structural elements, structural element nodes, geometry data, user-defined data (i.e., scalars, vectors and tensors). The domain is fixed: it does not grow automatically as model components expand or disperse, though its size may be re-specified with the extent command. Domain boundaries can have four conditions, which can be set by the condition command: destroy, stop, reflect, and periodic. As model components interact with the domain boundary, one of these conditions is applied. The default condition is the stop condition.

Enclosing a model within a domain — rather than allowing a model to float freely in infinite space — greatly enhances efficiency in searching and contact detection. This in turn improves performance of simulations.


  • Changes in the domain boundary condition take effect during the next timestep, and model components falling outside the domain are deleted if the domain size is changed.
  • Domains are mostly pertinent to PFC. In a FLAC3D model, only discrete fracture networks (DFNs) will be affected by the domain.