Kinematic Diffusivity error

lg88 · March 17, 2012, 04:37

Hi everybody
These days I have been studying a case of electric arc. I set an additional Variable name EPOT whose equation is diffusive transport equation.And I set the kinematic diffusivity as "Electric Conductivity/density*factorPhi".Electric Conductivity is also an additional Variable whose equation is algebraic equation.And its value I have set as constant.But when I run the case I met the following error:

Error processing expression 'Kinematic Diffusivity'.
The expression is invalid because:
Electric Conductivity is not available for use in this term

Error processing expression: Kinematic Diffusivity = Electric Conductivity/density*factorPhi

What is the problem?How can I solve it?Thank you very much!

lg88

ghorrocks · March 17, 2012, 06:12

Electrical conductivity does not appear on the list of available variables. I would set the electrical conductivity to equal a CEL expression, then you can use this CEL expression in calculations like this one.

lg88 · March 18, 2012, 10:07

Thanks to Glenn.I have set the electrical conductivity to equal a CEL expression.And the error has been solved.But I met a new problem when I run the case.
+--------------------------------------------------------------------+
| Reference Pressure Information |
+--------------------------------------------------------------------+

Domain Group: corus

Pressure has not been set at any boundary conditions.
The pressure will be set to 0.00000E+00 at the following location:
Domain : corus
Node : 1 (equation 1)
Coordinates : ( 1.33974E-09, 0.00000E+00,-5.00000E-02).

Details of error:-
----------------
Error detected by routine MAKDIR
CDRNAM = EPOT_FL1 /GRADIENT
CRESLT = ILEG

Current Directory : /FLOW/ALGORITHM/ZN1/SYSTEM/VARIABLES

what does it mean?How can I solve it?Thank you very much!

lg88

ghorrocks · March 18, 2012, 17:52

This looks like two independant problems. The first one is you have not set any pressure level, so it guessed one. You should define a pressure level in your simulation somehow - either a pressure inlet or outlet, initial condition or something.

The second problem is regarding a gradient calculation of electrical potential. Not sure about this one, I would fix the first problem and see if this persists. But it probably is unrelated to the pressure level problem.

March 17, 2012, 04:37	Kinematic Diffusivity error	#1
lg88 Member jack Join Date: Jul 2011 Posts: 52 Rep Power: 15	Hi everybody These days I have been studying a case of electric arc. I set an additional Variable name EPOT whose equation is diffusive transport equation.And I set the kinematic diffusivity as "Electric Conductivity/densityfactorPhi".Electric Conductivity is also an additional Variable whose equation is algebraic equation.And its value I have set as constant.But when I run the case I met the following error: Error processing expression 'Kinematic Diffusivity'. The expression is invalid because: Electric Conductivity is not available for use in this term Error processing expression: Kinematic Diffusivity = Electric Conductivity/densityfactorPhi What is the problem?How can I solve it?Thank you very much! lg88

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March 17, 2012, 06:12		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Electrical conductivity does not appear on the list of available variables. I would set the electrical conductivity to equal a CEL expression, then you can use this CEL expression in calculations like this one.

March 18, 2012, 10:07		#3
lg88 Member jack Join Date: Jul 2011 Posts: 52 Rep Power: 15	Thanks to Glenn.I have set the electrical conductivity to equal a CEL expression.And the error has been solved.But I met a new problem when I run the case. +--------------------------------------------------------------------+ \| Reference Pressure Information \| +--------------------------------------------------------------------+ Domain Group: corus Pressure has not been set at any boundary conditions. The pressure will be set to 0.00000E+00 at the following location: Domain : corus Node : 1 (equation 1) Coordinates : ( 1.33974E-09, 0.00000E+00,-5.00000E-02). Details of error:- ---------------- Error detected by routine MAKDIR CDRNAM = EPOT_FL1 /GRADIENT CRESLT = ILEG Current Directory : /FLOW/ALGORITHM/ZN1/SYSTEM/VARIABLES what does it mean?How can I solve it?Thank you very much! lg88

March 18, 2012, 17:52		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	This looks like two independant problems. The first one is you have not set any pressure level, so it guessed one. You should define a pressure level in your simulation somehow - either a pressure inlet or outlet, initial condition or something. The second problem is regarding a gradient calculation of electrical potential. Not sure about this one, I would fix the first problem and see if this persists. But it probably is unrelated to the pressure level problem.