CEL problem

jellio · March 5, 2010, 16:07

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,

John · March 5, 2010, 16:45

use /1[cm] to cancellate the unit

jellio · March 5, 2010, 17:10

Quote:

Originally Posted by John

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.

ghorrocks · March 6, 2010, 05:55

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.

John · March 6, 2010, 10:57

((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.

jellio · March 6, 2010, 12:39

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.

Bdew8556 · July 14, 2016, 06:15

Ha!

I've got one for ya.

Input from CFX-5 The problem was: INVALID-EXPONENTIATION FURTHER INFORMATION

This is from the static enthalpy at outlet, I haven't changed any pre set equations.

It happens when I try to run the gas compressor performance macro.

March 5, 2010, 16:07	CEL problem	#1
jellio New Member Join Date: Sep 2009 Posts: 5 Rep Power: 17	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,

March 6, 2010, 10:57		#5
John Member Join Date: Mar 2009 Posts: 49 Rep Power: 17	((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.*

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March 5, 2010, 16:45		#2
John Member Join Date: Mar 2009 Posts: 49 Rep Power: 17	use /1[cm] to cancellate the unit

March 6, 2010, 05:55		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	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.

March 6, 2010, 12:39		#6
jellio New Member Join Date: Sep 2009 Posts: 5 Rep Power: 17	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.

July 14, 2016, 06:15		#7
Bdew8556 Senior Member Brett Join Date: May 2013 Posts: 217 Rep Power: 14	Ha! I've got one for ya. Input from CFX-5 The problem was: INVALID-EXPONENTIATION FURTHER INFORMATION This is from the static enthalpy at outlet, I haven't changed any pre set equations. It happens when I try to run the gas compressor performance macro.