CEL expression for multiphase flow

cheche · April 19, 2010, 02:41

Hi everyone,

I am using CFX 12 to model airblast atomization. I'd like to have a look at the swirl of my flow to see if my particles are cought in any vortex zones and therefore would like to be able to look at the Stokes number.
in order to do this I have to define the eddy lifetime defined as:
t=0.3*k/epsilon

I have set up an expression "tee" defined as above, however I do I tell CFX that I am using the k corresponding to turbulent kinetic energy and the epsilon of dissipation rate??

What I'd like to be able to do is in CFX-post draw a line in my domain and chart my variable "tee" with respect to x or any other spatial variable.

Any help on this is greatly appreciated!!!

Cheers

Mat

ghorrocks · April 19, 2010, 06:43

The names of the CFX variables is listed in the documentation, in the CEL reference guide (it is in the CFX Reference guide I think). Also in CFD-Post you have a CEL helper which lists the available functions and variables. That can also help you get the names of the variables correct.

cheche · April 20, 2010, 20:54

Thanks for your help Glen, I will have a look at this.

Cheers

cheche · April 20, 2010, 21:31

Right so I have found what I was looking for, however I am not quite sure how to use it:

I have defined an expression tee as 0.3*ke/ed [s] and the corresponding variable Tee. If I plot a line or a plane for example in POST and want to color it according to the variable Tee I get the following error :

INTERNAL
Internal error detected:
could not fin variable Tee

I am guessing I have to tell CFX where I want to take the values of K and epsilon in the definition of my expression but how do I do this if I want to take the values of any random point where I am looking in my domain?

Any help is again much appreciated,

Cheers

mvoss · April 21, 2010, 03:30

hey,

create an new variable which is linked to your desired expression. that should do it.

neewbie

cheche · April 21, 2010, 09:16

Hey thanks for your reply,

unfortunately I don't think this is the issue here because I have linked my variable Tee to my expression tee (Tee-->tee, very subtle..) I really think it's something to do with the expression ke/ed and where CFX in my domain CFX takes the values of k and epsilon.

Thanks anyway!

April 19, 2010, 02:41	CEL expression for multiphase flow	#1
cheche New Member Mathieu Etcheparre Join Date: Aug 2009 Posts: 14 Rep Power: 16	Hi everyone, I am using CFX 12 to model airblast atomization. I'd like to have a look at the swirl of my flow to see if my particles are cought in any vortex zones and therefore would like to be able to look at the Stokes number. in order to do this I have to define the eddy lifetime defined as: t=0.3*k/epsilon I have set up an expression "tee" defined as above, however I do I tell CFX that I am using the k corresponding to turbulent kinetic energy and the epsilon of dissipation rate?? What I'd like to be able to do is in CFX-post draw a line in my domain and chart my variable "tee" with respect to x or any other spatial variable. Any help on this is greatly appreciated!!! Cheers Mat

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April 19, 2010, 06:43		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	The names of the CFX variables is listed in the documentation, in the CEL reference guide (it is in the CFX Reference guide I think). Also in CFD-Post you have a CEL helper which lists the available functions and variables. That can also help you get the names of the variables correct.

April 20, 2010, 20:54		#3
cheche New Member Mathieu Etcheparre Join Date: Aug 2009 Posts: 14 Rep Power: 16	Thanks for your help Glen, I will have a look at this. Cheers

April 20, 2010, 21:31		#4
cheche New Member Mathieu Etcheparre Join Date: Aug 2009 Posts: 14 Rep Power: 16	Right so I have found what I was looking for, however I am not quite sure how to use it: I have defined an expression tee as 0.3*ke/ed [s] and the corresponding variable Tee. If I plot a line or a plane for example in POST and want to color it according to the variable Tee I get the following error : INTERNAL Internal error detected: could not fin variable Tee I am guessing I have to tell CFX where I want to take the values of K and epsilon in the definition of my expression but how do I do this if I want to take the values of any random point where I am looking in my domain? Any help is again much appreciated, Cheers

April 21, 2010, 03:30		#5
mvoss Senior Member Matthias Voß Join Date: Mar 2009 Location: Berlin, Germany Posts: 449 Rep Power: 20	hey, create an new variable which is linked to your desired expression. that should do it. neewbie

April 21, 2010, 09:16		#6
cheche New Member Mathieu Etcheparre Join Date: Aug 2009 Posts: 14 Rep Power: 16	Hey thanks for your reply, unfortunately I don't think this is the issue here because I have linked my variable Tee to my expression tee (Tee-->tee, very subtle..) I really think it's something to do with the expression ke/ed and where CFX in my domain CFX takes the values of k and epsilon. Thanks anyway!