Missing physical domain tag information from vtk mesh format
 

Hi,
I am facing an issue while importing the mesh in .vtk format in Gmsh. I have generated a volumetric mesh and exported in vtk format. While importing the vtk mesh in Gmsh I am unable to define the physical entities.



My geometry is a cylinder inside the cube. I want to define the physical entities of each face of the cube, but while doing that I am unable to select each face of the cube. When I selected the surface all the surfaces including cylinder wall and the six faces of the cube are selected together.



Do you have any idea how to define the physical domain tag on each surface.


Thanks in advance