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

CEL problem

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 5, 2010, 16:07
Red face CEL problem
  #1
New Member
 
Join Date: Sep 2009
Posts: 5
Rep Power: 7
jellio is on a distinguished road
Hi,
I need some help to define a moving function by the expression, the following is the function I created:
(((0.8[cm])^2-(z-5[cm])^2)^0.5-((1.0-(z-5[cm])^2/(0.75[cm])^2)*(0.1[cm])^2)^0.5)*(t/tt)/0.4
When z=5.8[cm], which is supposed to be zero, while when I evaluate or run my simulation, an error shows up, as the following:
The problem was:
INVALID-EXPONENTIATION

FURTHER INFORMATION

The problem was encountered in executing the expression for:
value
The complete expression is: (((0.8[cm])^2-(z-5[cm])^2)^0.5-((1.0-(z-5[cm])^2/(0.
The error occurs on sub-expression: ((0.8[cm])^2-(z-5[cm])^2)^0.5

BACKGROUND INFORMATION



These values were set before reaching the current expression:

Name = Expression = Value

tt = 1 [s] = 1.00000

END OF DIAGNOSTIC OUTPUT FOR CFX EXPRESSION LANGUAGE

Can Anyone point out how to solve it? I really appreciate!
Thanks,
jellio is offline   Reply With Quote

Old   March 5, 2010, 16:45
Default
  #2
Member
 
Join Date: Mar 2009
Posts: 48
Rep Power: 8
John is on a distinguished road
use /1[cm] to cancellate the unit
John is offline   Reply With Quote

Old   March 5, 2010, 17:10
Default
  #3
New Member
 
Join Date: Sep 2009
Posts: 5
Rep Power: 7
jellio is on a distinguished road
Quote:
Originally Posted by John View Post
use /1[cm] to cancellate the unit
No, it not the units problem, the problem appears only when z=5.8cm, which should be zero.
jellio is offline   Reply With Quote

Old   March 6, 2010, 05:55
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,814
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
I suspect you will need to put more brackets in it to ensure the order of operations is correct. I suspect it is evaluating something like 1.0-(z-5[cm])^{2/(0.75[cm])^2} (the curly brackets are my addition) and that is an invalid operation due to the units of the exponential operation.
ghorrocks is online now   Reply With Quote

Old   March 6, 2010, 10:57
Default
  #5
Member
 
Join Date: Mar 2009
Posts: 48
Rep Power: 8
John is on a distinguished road
((1.0-(z-5[cm])^2/(0.75[cm])^2)*(0.1[cm])^2)^0.5 appears to be invalid, it is a (negative vlaue)^0.5 at higher Z value.

Last edited by John; March 6, 2010 at 11:48.
John is offline   Reply With Quote

Old   March 6, 2010, 12:39
Smile
  #6
New Member
 
Join Date: Sep 2009
Posts: 5
Rep Power: 7
jellio is on a distinguished road
yes, thanks John, it seems there is one point in the plane I want to use the function exceed 5.8 for just a little, but it does influence, I just made some modification, it works now.

thanks again for all.
jellio is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
UDF compiling problem Wouter Fluent UDF and Scheme Programming 6 June 6, 2012 04:43
Incoherent problem table in hollow-fiber spinning Gianni FLUENT 0 April 5, 2008 10:33
Adiabatic and Rotating wall (Convection problem) ParodDav CFX 5 April 29, 2007 19:13
Problem in Tutorial problem of fluent Phanindra FLUENT 5 April 17, 2007 09:57
Is this problem well posed? Thomas P. Abraham Main CFD Forum 5 September 8, 1999 14:52


All times are GMT -4. The time now is 20:25.