Setting Types
STAR-CCM+ initially assigns types during mesh import (based on information that is contained in the mesh being imported) or when a region or boundary is created from within the simulation.
To change the type of a region, boundary or interface, select the region, boundary, or interface in the object tree. In the Properties window, select one of the available types from the drop-down list corresponding to the Type property.

The models that are available in the continuum determine the list of available types. For instance, the Free Stream boundary type is only valid for ideal gas flow. So if the continuum does not contain the Ideal Gas Model, the Free Stream boundary type is not presented.