I couldn't find the direct method/command to export a .msh file from Fluent (v19.1). Instead I'm doing the followings to get the .msh file from .cas file:
- In Fluent Solution Mode (normal mode), write a .cas file
- Launch Fluent in the Meshing Mode by ticking "Meshing Mode" in the Fluent Launcher
- Read the .cas file just saved by File>Read>Mesh... then it prompt "Reading a case file as a mesh file results in loss of boundary conditions." Press OK.
- Write the mesh as .msh by File>Write>Mesh...