setup K,E parameters in CFX 13

fek66 · May 15, 2011, 05:10

HE ALL ;
I want to pass parameters for sigma k and e in k-Epsilon Model with CEl Function ; it seem that it's not permit in CFX 13. wich accept only constants . is there any file or env varaiable to edit and change to make CFX 13 accpet CEL function .
thanks

ghorrocks · May 15, 2011, 19:59

You may be able to do this by editting the <CFX_ROOT>/etc/VARIABLES file. But no guarantees, and remember that the reason you cannot define it as a variable is because it is not properly implemented in the solver and all the cross terms which arise from this are not accounted for. In other words - "At your own risk!"

fek66 · May 18, 2011, 05:55

it's not possible to pass with Cel function , also changing to version 12.1 same result , for this closure parameter CFX accept only constant perhaps it's a limitation of CFX ?

ghorrocks · May 18, 2011, 07:06

Quote:

perhaps it's a limitation of CFX ?

Yes, precisely. When you allow numbers like this to vary it introduces lots of yukky cross terms and these can be fiendishly complex and frequently numerically unstable.

Why do you want them to vary anyway? It means you will not be using the k-e turbulence model. What is different about your model to require it?

fek66 · May 19, 2011, 12:21

Hi ghorrocks;
I use K-Eps model , but i wan't to pass values for sigma_E ( dissipation) with CEL function as follow:
sigma_E = if( z< seuil, 0.5, 1.3) that means the value is 0.5 or 1.3.

ghorrocks · May 19, 2011, 19:49

Why do you want to do this?

fek66 · May 20, 2011, 15:55

to check the possibility of enhancement of concentration prediction

ghorrocks · May 21, 2011, 08:54

I see.

Have you tried editting the VARIABLES file as suggested?

fek66 · May 21, 2011, 19:01

Yes I edited the VARIABLES file but there is no ligne pointing to this parameters to change it.

May 15, 2011, 05:10	setup K,E parameters in CFX 13	#1
fek66 Member anonymous Join Date: Jan 2011 Posts: 42 Rep Power: 15	HE ALL ; I want to pass parameters for sigma k and e in k-Epsilon Model with CEl Function ; it seem that it's not permit in CFX 13. wich accept only constants . is there any file or env varaiable to edit and change to make CFX 13 accpet CEL function . thanks

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May 15, 2011, 19:59		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	You may be able to do this by editting the <CFX_ROOT>/etc/VARIABLES file. But no guarantees, and remember that the reason you cannot define it as a variable is because it is not properly implemented in the solver and all the cross terms which arise from this are not accounted for. In other words - "At your own risk!"

May 18, 2011, 05:55		#3
fek66 Member anonymous Join Date: Jan 2011 Posts: 42 Rep Power: 15	it's not possible to pass with Cel function , also changing to version 12.1 same result , for this closure parameter CFX accept only constant perhaps it's a limitation of CFX ?

May 19, 2011, 12:21		#5
fek66 Member anonymous Join Date: Jan 2011 Posts: 42 Rep Power: 15	Hi ghorrocks; I use K-Eps model , but i wan't to pass values for sigma_E ( dissipation) with CEL function as follow: sigma_E = if( z< seuil, 0.5, 1.3) that means the value is 0.5 or 1.3.

May 19, 2011, 19:49		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	Why do you want to do this?

May 20, 2011, 15:55		#7
fek66 Member anonymous Join Date: Jan 2011 Posts: 42 Rep Power: 15	to check the possibility of enhancement of concentration prediction

May 21, 2011, 08:54		#8
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	I see. Have you tried editting the VARIABLES file as suggested?

May 21, 2011, 19:01		#9
fek66 Member anonymous Join Date: Jan 2011 Posts: 42 Rep Power: 15	Yes I edited the VARIABLES file but there is no ligne pointing to this parameters to change it.