Question on vacuum chamber

paolo.pizzol · April 5, 2016, 06:15

Hi all

I am in need of simulating the flow of 100 sccm of Argon inside a chamber at 5 mbar. Which solver should I use? RhoFoam or PisoFoam? How and where do I set the pressure for the chamber?

Thanks!

Paolo

akidess · April 5, 2016, 07:00

Have you checked the Knudsen number?

paolo.pizzol · April 5, 2016, 07:16

Nope, I'm afraid I haven't. I just went online to calculate it, and it seems to be in the 10-5 / 10-6 range... is it helpful?

akidess · April 5, 2016, 10:19

That seems very small for a vacuum, but of course you didn't give a lot of details on your problem, so let's assume it's true, then you can use continuum mechanics. Now, determine if your density is constant and you'll know if you can use pisoFoam or not.

paolo.pizzol · April 5, 2016, 10:51

Thanks for the suggestion akidess :-)

To be a bit more specific, I have a cylindrical chamber of about 20 cm of length and 10 cm in diameter. The chamber is constantly being pumped, so it has a base pressure of about 10^-3 mbar. I know from experiments that when I inject the gas (from the centre of the base of the cylinder) the pressure raises to about 5 mbar and stays there.

I would imagine that after the initial few moments (seconds maybe?), since the pressure is constant, the gas density would also be constant.

...although I may be completely wrong :-)

Any hints?

Thanks!

Paolo

April 5, 2016, 06:15	Question on vacuum chamber	#1
paolo.pizzol New Member PaoloP Join Date: Jan 2016 Posts: 5 Rep Power: 10	Hi all I am in need of simulating the flow of 100 sccm of Argon inside a chamber at 5 mbar. Which solver should I use? RhoFoam or PisoFoam? How and where do I set the pressure for the chamber? Thanks! Paolo

April 5, 2016, 07:00		#2
akidess Senior Member Anton Kidess Join Date: May 2009 Location: Germany Posts: 1,377 Rep Power: 29	Have you checked the Knudsen number? __________________ On twitter @akidTwit Spend as much time formulating your questions as you expect people to spend on their answer.

April 5, 2016, 10:19		#4
akidess Senior Member Anton Kidess Join Date: May 2009 Location: Germany Posts: 1,377 Rep Power: 29	That seems very small for a vacuum, but of course you didn't give a lot of details on your problem, so let's assume it's true, then you can use continuum mechanics. Now, determine if your density is constant and you'll know if you can use pisoFoam or not. __________________ On twitter @akidTwit Spend as much time formulating your questions as you expect people to spend on their answer.

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April 5, 2016, 07:16		#3
paolo.pizzol New Member PaoloP Join Date: Jan 2016 Posts: 5 Rep Power: 10	Nope, I'm afraid I haven't. I just went online to calculate it, and it seems to be in the 10-5 / 10-6 range... is it helpful?

April 5, 2016, 10:51		#5
paolo.pizzol New Member PaoloP Join Date: Jan 2016 Posts: 5 Rep Power: 10	Thanks for the suggestion akidess :-) To be a bit more specific, I have a cylindrical chamber of about 20 cm of length and 10 cm in diameter. The chamber is constantly being pumped, so it has a base pressure of about 10^-3 mbar. I know from experiments that when I inject the gas (from the centre of the base of the cylinder) the pressure raises to about 5 mbar and stays there. I would imagine that after the initial few moments (seconds maybe?), since the pressure is constant, the gas density would also be constant. ...although I may be completely wrong :-) Any hints? Thanks! Paolo