Where do I start ?
 

Hi
I am mechanichal eng.
I want to make wind tunnel analysis.
I want to draw and simulate then do desicion.

Which tool(s) I have to use.

You will either need to make your solid geometry in Gambit, or another program (Solidworks, Autocad...).

Then you will need to mesh your geometry in Gambit.

The simulations can then be run in Fluent.

What about CATIA for mechanical design

I using Solidwork. Export parasolid files (.x_t) to gambit.
Gambit import the parasolid files (.x_t) and mesh it then export mesh files (.msh)
Fluent will import mesh files (.msh) and do simulation.

Just for your reference.
I personally think that parasolid is the best solution to import solid geometry into Gambit.