For body-fitted meshes, the region definitions must be specified as flags associated with the mesh itself, following the KIVA-3V export convention. In this case, after importing the mesh, the regions will already appear in the Initial Conditions list, a Region ID is automatically assigned, and there is no need to map the regions to any geometry surface. For these regions, you need only set the initial variable values, as described for the Initialization panel in Initialization Panel.