CEL expression in CFX-pre

Anna Tian · June 29, 2013, 14:17

Hi

I'd like to define a position dependent variable by:

'
length = 0.0033 [m]
a = 0.1-x/length*(0.1-0.07) [m s^-1]
'
.

But the error message is

'
Units ([m s^-1]) are associated with a term that is not dimensionless.
'

It is quite strange because the unit of 'x' is [m], right? So 'x/length' should be already dimensionless. Why it is still reported as 'not dimensionless'? I'm really confused. Could anyone help?

cdegroot · June 29, 2013, 15:02

You need to put dimensions on the first 0.1 as well. I would also put the units on the second 0.1 and the 0.07 separately. I've never tried factoring out the units like you did there but I'm not so sure it is valid. I would write as

a = 0.1 [m s^-1] -x/length*(0.1 [m s^-1]-0.07 [m s^-1])

Or better yet, factor the 0.1 and 0.07 into their own variables.

June 29, 2013, 14:17	CEL expression in CFX-pre	#1
Anna Tian Senior Member Meimei Wang Join Date: Jul 2012 Posts: 494 Rep Power: 15	Hi I'd like to define a position dependent variable by: ' length = 0.0033 [m] a = 0.1-x/length*(0.1-0.07) [m s^-1] ' . But the error message is ' Units ([m s^-1]) are associated with a term that is not dimensionless. ' It is quite strange because the unit of 'x' is [m], right? So 'x/length' should be already dimensionless. Why it is still reported as 'not dimensionless'? I'm really confused. Could anyone help? __________________ Best regards, Meimei

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
How to specify a polyline or plane in CFX Expression Language (CEL) in CFX-Pre?	francis1	CFX	5	February 6, 2013 10:16
air ideal gas in CFX Pre	wangy1767	CFX	9	October 1, 2012 07:55
Create a virtual Surface into a domain in CFX PRE	chuck209	Main CFD Forum	0	August 13, 2012 12:10
Conditional Expression in CFX Pre	ashtonJ	CFX	83	May 28, 2012 03:49
CFX Pre - TGrid	Vivek Vasudevan	CFX	2	March 20, 2007 06:31

June 29, 2013, 15:02		#2
cdegroot Senior Member Chris DeGroot Join Date: Nov 2011 Location: Canada Posts: 414 Rep Power: 17	You need to put dimensions on the first 0.1 as well. I would also put the units on the second 0.1 and the 0.07 separately. I've never tried factoring out the units like you did there but I'm not so sure it is valid. I would write as a = 0.1 [m s^-1] -x/length*(0.1 [m s^-1]-0.07 [m s^-1]) Or better yet, factor the 0.1 and 0.07 into their own variables.