[Gmsh] generate surfaces from mesh

[forti]

Hi,

I am a PhD student working at EPFL (CMCS group) with LifeV on 
fluid-structure interaction problems. I have a mesh of the structure 
domain (which represents a blood-vessel) in a *.mesh file (containing 
informations only about Vertices and Tetrahedra) and the final goal 
would be to generate the inner fluid mesh starting from the structure 
one. Moreover,  starting from the mesh of the structure, I need to 
generate surfaces (e.g. the one representing the fluid-structure 
interface) in order to assign it to a physical entity. Could you please 
help me?

Thank you in advance,
Davide