droplet absorption diameter

Claudia · March 31, 2010, 13:54

Hi,

I have a subdomain in which I want to remove particles from the domain. I know that I can use the "Absortion diameter". But now my question:

The absorption diameter depends on the gas velocity, is it possible to implement this dependency? I tried to do something like

absorption diameter = function of Velocity w,

but the following error occurs:

"Velocity w is not available for use in this term"

Does anyone has an idea?

Thanks in advance
Claudia

ghorrocks · March 31, 2010, 19:07

The message is quite clear - you can't make absorption diameter a function of W velocity. Some variables can only be constants or functions of a subset of variables and I think you have found one. If you really need to do this talk to CFX support and they may be able to find a work around for you.

a.m. · April 1, 2010, 03:15

try to create an expression in cfx pre like absorption diameter = f(velocity w), then use this expression in subdomain.

in expression you should use direct difinition, e.g.
"massflowave(Velocity W)@inlet*1[s]"
it means than your absorption diameter will be equal average velocity w in inlet BC

Claudia · April 1, 2010, 08:30

Thanks, Glenn for your answer. So I have to tell the support about it and I hope they will find a workaround.

ghorrocks · April 2, 2010, 07:14

Yes, that's right. There will be a reason the absorption diameter cannot be set as a function of velocity. If you bypass the check, it may or may not affect your results - so talk to them and try to find out.

March 31, 2010, 13:54	droplet absorption diameter	#1
Claudia Member Join Date: Mar 2009 Posts: 38 Rep Power: 17	Hi, I have a subdomain in which I want to remove particles from the domain. I know that I can use the "Absortion diameter". But now my question: The absorption diameter depends on the gas velocity, is it possible to implement this dependency? I tried to do something like absorption diameter = function of Velocity w, but the following error occurs: "Velocity w is not available for use in this term" Does anyone has an idea? Thanks in advance Claudia

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March 31, 2010, 19:07		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	The message is quite clear - you can't make absorption diameter a function of W velocity. Some variables can only be constants or functions of a subset of variables and I think you have found one. If you really need to do this talk to CFX support and they may be able to find a work around for you.

April 1, 2010, 03:15		#3
a.m. New Member Alex Join Date: Mar 2010 Location: Russia Posts: 19 Rep Power: 16	try to create an expression in cfx pre like absorption diameter = f(velocity w), then use this expression in subdomain. in expression you should use direct difinition, e.g. "massflowave(Velocity W)@inlet*1[s]" it means than your absorption diameter will be equal average velocity w in inlet BC

April 1, 2010, 08:30		#4
Claudia Member Join Date: Mar 2009 Posts: 38 Rep Power: 17	Thanks, Glenn for your answer. So I have to tell the support about it and I hope they will find a workaround.

April 2, 2010, 07:14		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	Yes, that's right. There will be a reason the absorption diameter cannot be set as a function of velocity. If you bypass the check, it may or may not affect your results - so talk to them and try to find out.