CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > CFX

Startup Additional Variables

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 2, 2011, 20:39
Post Startup Additional Variables
  #1
New Member
 
FM
Join Date: Feb 2010
Posts: 14
Rep Power: 16
Felipe Matos is on a distinguished road
Hi

I'm trying to simulate a problem which requires an Additional Variable "av". The domain's DENSITY is a function of this av: DENSITY = f (av). This av is a function of TEMPERATURE: av = f (TEMPERATURE).

I give the initial temperature, but at the initialization of the run, appears an error:
"Error processing expression 'Density'.
The expression is invalid because: Dano is not available for use in this term"

I think this is because I didn't find anywhere to put an inital value of the av. Where can I initialize the av? If I can't, what can I do?

Thanks
Felipe Matos is offline   Reply With Quote

Old   February 3, 2011, 15:44
Default
  #2
Senior Member
 
Join Date: Mar 2009
Location: Europe
Posts: 169
Rep Power: 17
joey2007 is on a distinguished road
To be honest: i do not fully understand what you intend to do.

There are different kinds of av. If you chose the option transport equation it is possible to initialize. The type algebraic equation should depend on other variables, so it is not required to initialize.
__________________
-
-
-
-
-
------------------------------------------------------------------------
Please do not forget: I am not paid for answering your questions.


Thousands of issues can cause a division by zero. Please do not capture a thread, with the argument: "I have the same issue ...."
joey2007 is offline   Reply With Quote

Old   February 3, 2011, 19:49
Default
  #3
New Member
 
FM
Join Date: Feb 2010
Posts: 14
Rep Power: 16
Felipe Matos is on a distinguished road
My av is an Algebraic Expression. Like I said: Density = f (av) and av = f (T).
I think the problem is because the CFX initializes first its own variables (like Temperature, COndutivity, Density...); but my Density is a function of the av created, that is initialized olny after this primitive variables.

I don't know if the problem is this... Can anyone help?

Thanks
Felipe Matos is offline   Reply With Quote

Old   February 4, 2011, 06:33
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,665
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
I can't check this but I suspect you cannot made density a function of a additional variable. There are only limited variables you can make density a function of. You will have to specify density as a direct function of temperature.
ghorrocks is offline   Reply With Quote

Old   March 28, 2011, 23:59
Default
  #5
New Member
 
eric
Join Date: Nov 2010
Location: Vancouver, Canada
Posts: 16
Rep Power: 15
armyou is on a distinguished road
Quote:
Originally Posted by ghorrocks View Post
I can't check this but I suspect you cannot made density a function of a additional variable. There are only limited variables you can make density a function of. You will have to specify density as a direct function of temperature.
Yeah, CFX11 Pre would show error information if additional variable is applied in density. In CFX12, although there is no any error or warning information in CFX pre, slover would be stopped because of the additional variable dependent density.

Glenn, do you think it is possible to solve this problem by using subroutine in CFX?

Actually I donot understand why CFX has such a limitation, is it because CFX can not initialize the density if additional variable is included?
armyou is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
ADDITIONAL VARIABLES LIMITERS N.P CFX 5 December 1, 2011 08:47
what is boundary-only additional variables? frank CFX 0 September 6, 2008 23:11
additional variables' effect ariel CFX 9 April 2, 2008 01:41
user SUBROUTINE for additional variables Tuks CFX 0 November 8, 2005 03:09
Replace periodic by inlet-outlet pair lego CFX 3 November 5, 2002 21:09


All times are GMT -4. The time now is 05:33.