Total mass flow

MrFEA · November 22, 2010, 10:23

Hi Folks

I'm simulating a chamber pumpdown using a getter. The pumpdown speed depends on the total mass sorbed by the getter (I have the model for that).

What would be the variable for the cumulative mass flow through an outlet? Or would it be possible to integrate over time?

thx for the help

RossFS · November 22, 2010, 16:00

You could do a numerical integration via a CEL expression. Not sure on the variable though - I have no knowledge in this area.

ghorrocks · November 22, 2010, 17:29

Sorry, but no. You cannot do time integrals in CEL. If you have to do time integrals you will need to do it in fortran.

RossFS · November 22, 2010, 17:57

So CFX does not have an internal time value that can be used/addressed?

ghorrocks · November 22, 2010, 18:10

Yes, CFX does have a time value. But CEL values do not persist between time steps so there is no way to accumulate over time. You could make a fortran CEL function to do the accumulation over time and normal CEL to do everything else. This is not too hard to do.

MrFEA · November 23, 2010, 05:41

Thanks for the comments. So, it seems I'm stuck here. I'll work on something. Thank you again

MrFEA · November 24, 2010, 11:59

So fa rthe only solution is to use "mass()@domain". The total mass out of the domain is initial mass - mass()@domain. It seems to work. Now I just need the folks from SAES to send me some data.

Take care

November 22, 2010, 10:23	Total mass flow	#1
MrFEA New Member Enio Carpi Join Date: Apr 2010 Posts: 12 Rep Power: 16	Hi Folks I'm simulating a chamber pumpdown using a getter. The pumpdown speed depends on the total mass sorbed by the getter (I have the model for that). What would be the variable for the cumulative mass flow through an outlet? Or would it be possible to integrate over time? thx for the help

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November 22, 2010, 16:00		#2
RossFS Member Join Date: Feb 2010 Location: Australia Posts: 65 Rep Power: 16	You could do a numerical integration via a CEL expression. Not sure on the variable though - I have no knowledge in this area.

November 22, 2010, 17:29		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Sorry, but no. You cannot do time integrals in CEL. If you have to do time integrals you will need to do it in fortran.

November 22, 2010, 17:57		#4
RossFS Member Join Date: Feb 2010 Location: Australia Posts: 65 Rep Power: 16	So CFX does not have an internal time value that can be used/addressed?

November 22, 2010, 18:10		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Yes, CFX does have a time value. But CEL values do not persist between time steps so there is no way to accumulate over time. You could make a fortran CEL function to do the accumulation over time and normal CEL to do everything else. This is not too hard to do.

November 23, 2010, 05:41		#6
MrFEA New Member Enio Carpi Join Date: Apr 2010 Posts: 12 Rep Power: 16	Thanks for the comments. So, it seems I'm stuck here. I'll work on something. Thank you again

November 24, 2010, 11:59		#7
MrFEA New Member Enio Carpi Join Date: Apr 2010 Posts: 12 Rep Power: 16	So fa rthe only solution is to use "mass()@domain". The total mass out of the domain is initial mass - mass()@domain. It seems to work. Now I just need the folks from SAES to send me some data. Take care