Gasflow into vacuum
 

Hello,
I'm totally new to CFD and thus to OpenFOAM. I've been playing around with the tutorials for quite a time and wanted to start simulating my own problem now.
For my job at a university group in Hamburg (Germany) I should simulate the flow of an ideal gas through a nozzle into a vacuum chamber.

On my first tries I got lots of errors (mostly to high Courant numbers) while trying to adapt the "compressible/sonicFoam/laminar/forwardStep" to my mesh and testing it.

1) Is sonicFoam able to simulate such a flow?
2) which boundary conditions are the best for simulating an input of some bars of pressure and how to model the vacuum chamber?

Unfortunately didn't I find appropriate answers in existing threats.
Thanks
Max

Hey Max,

I'm working on a similar project where I am simulating air flow into a vacuum chamber through a controlled leak (0.5 mm ID capillary). I used rhoCentralFoam to get a transient solution. I'm not done with the project yet but I have obtained some reasonable results.

You may want to check out the LadenburgJet60psi tutorial in the rhoCentralFoam section. This helped me greatly when I was first starting.

I hope this helps! Keep me updated as it is always good to be in touch with others working on similar projects.

Regards,

Eric

Hey Eric,

thanks for your reply. I'll keep you posted as soon as I make any progress.

Regards,
Max

create vacuum inside chamber....!!???
 

Hello Max and Eric

I am doing my M.tech Project at Mumbai University,India. I am simulating vacuum chamber in my simulation.

I am working on Physical vapor deposition. To improve coating quality I have to maintain vacuum of level 0.005 pascal and my geometry is a vertical cylinder of 300 mm dia and 640mm height and horizontal cylinder of 100 mm height and 150mm dia is connected with the vertical cylinder at the height of 150mm from the bottom. the horizontal cylinder on another side is connected with vacuum pump which create vacuum of 0.005 pascal.

I have given boundary condition as pressure outlet.

So can you please help me how should I set my operating pressure and gauge pressure for pressure outlet BC so I can maintain 0.005 pa vacuum inside the chamber.

I am simulating my problem using species transport model with volumetric reaction.

waiting for replay

thanks in advance

Hey did you have any luck in knowing how to set operating pressure and gauge for BC for this vacuum conditions? I am dealing with similar problem
Thanks in advance

Beware of Kn >> 1
 

Dear Vaaj,

Although the topic is rather old, I wish you the best of luck with getting good answers!
Unfortunately I cannot answer your main question.
But I would like to remind of a critical piece of the analysis:
Be careful about the different requirements for a simulation with the different solvers! Most of the OF-solvers are based on the continuum-approach, requiring a Knudsen number << 1 for giving scientifically meaningful results!

For the briefest of informations, have a look at http://www.thermopedia.com/content/908/

Cheers,
Bernhard