Dear Fluent Users, I am trying to modell a high-speed gas jet, which is exausting into a vacuume chamber. I have tried almost all possiblilities that I could think about.

Seggragated, coupled, invisid and RNG based models, but non of the above seems to work. The flow simply diverges. Modelling the same problem in the ambient atmosphere is no problem, the flow converges nicely.

Is there any fluent user who might have some experience in this area, especially vacuume technology. Your help will be most gratifying and thank you in advance.

What operating conditions have you specified?

Prasad

Hi Prasad,

I am working with pressure inlet and outlet boundary conditions. The inlet boundary is for helium at 8bar and the outlet, which is the vacuumm pressure of 0.001bar. The fluid is exhusting a De-Laval nozzle into the chamber.

Any thought on this, your help would much appriciated.

Hi,

are you sure that the outlet conditions as specified above are realistic..? What I would suggest you is to try to model this jet in transient mode and just for the start not using any outlet at all - try rather large vacuum chamber. It seems probable to me that the outlet condition is causing your problems. BTW - are you modelling an experimental vacuum or a jet motor e.g. in a spaceship? In the latter case maybe far-field boundary condition would be more appropriate. If you'll have any success, give us a note, this is quite interesting.

Bye George