hi. how to do a vaccum in Fluent (P=0Pa) inside a box??? thank you in advance.

your problem is not clear.. btw you may use the continuum boundary condition in gambit and intitalize the flow inside the box independently.

My probblem (and quastion) is: is it possible to set pressure inside any volume (like some box..., like internal part of flat plate sollar collector, like space in cosmos) pressure to 0. During calculation process there is no pressure change. I hope I explained something more. Just want to have pressure 0 in my calculation domain... btw thank you for your help

Do I have to just set all pressures to 0? Will there not be any errors??

Use "patch" command in Fluent after declaring the volume as a zone (in gambit). In reality, there is no perfect vacuum where pressure is zero..You can use extremely small pressures (~10^-3 10^-4...depending on smallest pressure limit for continuum flow)

Rajesh

thank you very much regards gb