Improving resolution of the mesh
 

Hi, I have a geometry imported from ProE into Gambit. I have created a cylinder (in GAMBIT) around the solid (the idea is that the solid model is put into a tube). Then I attached another cylinder to the distal part of the first cylinder - meaning thefirst cylinder is connected to the second one. For this should I use the UNION function in GAMBIT? Or is it OK if I just move/ align the two so that the distal face of the first coincides with the proximal face of the first and thus make them appear as if they are connected?

Now,my idea is to mesh the mesh the flow field within and around the solid. For this, I subtracted the volume of the solid from the volume of the first cylinder and then meshed all the volumes. Is this procedure OK? Now, my problem is that the mesh is triangular and very very coarse. Is there any way to improve its resolution and if so, how can I do it? Do I have to use sizing function? I do not know how exactly to apply them. Can anyone help me out with this?

Thanks, Vidya