During mesh generation in STAR-CCM+, the original imported geometry may be lacking sufficient boundaries in order for the regions to be properly demarcated. In particular, it is a frequent occurrence that a shared or common boundary is used for inter-region surfaces whereas the requirements for multi-region meshing impose that two separate boundaries must exist in order for the regions to be properly defined. Converting a boundary to an interface allows this requirement to be met.
When a boundary is converted to an interface, two separate actions occur:
The copy of the original boundary can then be used as part of the definition of a new region, for example, by using the create new region from boundaries option. This process will also automatically move the interface node copy into the appropriate region.