Local control over the initial mesh within a sub-volume of a solid can be achieved by defining the sub-volume with a "mesh control" solid. To use this method you create the "mesh only" solid, then set its meshing properties and proceed with your simulation. The same model and assumptions described in “Local Control Using Mesh Constraints” are used.
Once the sub-volume of interest is created, set an element size on it using either solid parameters or a mesh constraint.
Set the Mesh Control Only parameter on the sub-volume to "True". This causes the mesher to do the region for you.
Note that the "Mesh Control Only" solids are rendered in a light gray. The Material parameter is invisible as it is irrelevant, and the icon changes in the tree.
Unlike manually creating the Boolean region there is no need to worry about attribute assignments as the topology of the original solid is not impacted. No additional faces/edges are added to the model to complicate picking.