Error in defining expression

aja1345 · August 12, 2016, 07:09

Hi,

I am defining an expression, but i have a error as follows:

Why does this happen?

Thanks.

urosgrivc · August 12, 2016, 07:24

What does this mean? )(
try )*( multiplication if this is what you want?

aja1345 · August 12, 2016, 07:34

Quote:

Originally Posted by urosgrivc

What does this mean? )(
try )*( multiplication if this is what you want?

Yes!!! Thanks

aja1345 · August 12, 2016, 09:10

Hi,

Why does the following error happen?

I want to define gas constant of air.

aja1345 · August 12, 2016, 10:07

Why does unit of the following expression equal to Kg^2 m s^-5 K^-2?

volumeInt(((Thermal Conductivity/(Temperature)^2)*((1/(Density*(R/(M air))))*(Pressure.Gradient X)^2+(1/(Density*(R/M air)))*(Pressure.Gradient Y)^2+(1/(Density*(R/M air)))*(Pressure.Gradient Z)^2)))@Rotary

R=gas constant

According to above, Unit of Volume integral should be equal to kg m^2/S^-3 K^-1 . I assumed fluid as ideal gas presently. therefore>>>>> P=Ro*R*T

T=P/(RO*T)

.........

Thanks.

urosgrivc · August 14, 2016, 14:08

I dont think that [Kj] means enithing.
definitly not with smal j

I am asking the experts now-> (is kilo(k) , mega(M) and other prefixes suported instead of multipliers) as I havent tried it out myself.

Joul=J should work but than, for Kilo you should multiply it by 1000.
so you would end up with [J kg^-1 K^-1]*1000

ghorrocks · August 14, 2016, 19:31

Yes, CFX supports the SI unit system with prefixes. But you have to get it correct, as urosgrivc states. Joule is J and kilo prefix is k, so the unit if kJ.

aja1345 · August 15, 2016, 07:15

Thanks.

What is your suggestion about defining expression?

I am grateful that guide me about this case.

ghorrocks · August 15, 2016, 07:41

I think the temperature gradient functions work in CFD-Post. Have a look in the CFX reference manual for a description of the available variables and functions you can apply to them.

Also the temperature gradient variables will be available under the puzzlingly titled "..." button for plotting on surfaces, vectors etc.

aja1345 · August 15, 2016, 15:28

Quote:

Originally Posted by ghorrocks

Also the temperature gradient variables will be available under the puzzlingly titled "..." button for plotting on surfaces, vectors etc.

Thanks.

I don't understand this your statement. Can you explain more?

What is "..." button?

Opaque · August 15, 2016, 15:42

Insert an User Defined Variable, for the method select Gradient, and select Temperature for the variable. CFD-Post will create the Temperature.Gradient variable.

You can then use it as needed.

August 12, 2016, 07:09	Error in defining expression	#1
aja1345 Senior Member Aja Join Date: Nov 2013 Posts: 496 Rep Power: 14	Hi, I am defining an expression, but i have a error as follows: Why does this happen? Thanks. Last edited by aja1345; August 16, 2016 at 08:06.

August 12, 2016, 07:24		#2
urosgrivc Senior Member urosgrivc Join Date: Dec 2015 Location: Slovenija Posts: 365 Rep Power: 11	What does this mean? )( try )*( multiplication if this is what you want? aja1345 likes this.

August 12, 2016, 09:10		#4
aja1345 Senior Member Aja Join Date: Nov 2013 Posts: 496 Rep Power: 14	Hi, Why does the following error happen? I want to define gas constant of air. Last edited by aja1345; August 16, 2016 at 08:05.

August 12, 2016, 10:07		#5
aja1345 Senior Member Aja Join Date: Nov 2013 Posts: 496 Rep Power: 14	Why does unit of the following expression equal to Kg^2 m s^-5 K^-2? volumeInt(((Thermal Conductivity/(Temperature)^2)((1/(Density(R/(M air))))(Pressure.Gradient X)^2+(1/(Density(R/M air)))(Pressure.Gradient Y)^2+(1/(Density(R/M air)))(Pressure.Gradient Z)^2)))@Rotary R=gas constant According to above, Unit of Volume integral should be equal to kg m^2/S^-3 K^-1* . I assumed fluid as ideal gas presently. therefore>>>>> P=RoRT T=P/(ROT) ......... Thanks. Last edited by aja1345; September 7, 2016 at 12:11.*

August 14, 2016, 14:08		#6
urosgrivc Senior Member urosgrivc Join Date: Dec 2015 Location: Slovenija Posts: 365 Rep Power: 11	I dont think that [Kj] means enithing. definitly not with smal j I am asking the experts now-> (is kilo(k) , mega(M) and other prefixes suported instead of multipliers) as I havent tried it out myself. Joul=J should work but than, for Kilo you should multiply it by 1000. so you would end up with [J kg^-1 K^-1]*1000 aja1345 likes this.

August 14, 2016, 19:31		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,716 Rep Power: 143	Yes, CFX supports the SI unit system with prefixes. But you have to get it correct, as urosgrivc states. Joule is J and kilo prefix is k, so the unit if kJ. aja1345 likes this.

August 15, 2016, 07:15		#8
aja1345 Senior Member Aja Join Date: Nov 2013 Posts: 496 Rep Power: 14	Thanks. What is your suggestion about defining expression? I am grateful that guide me about this case. Last edited by aja1345; August 16, 2016 at 08:08.

August 15, 2016, 07:41		#9
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,716 Rep Power: 143	I think the temperature gradient functions work in CFD-Post. Have a look in the CFX reference manual for a description of the available variables and functions you can apply to them. Also the temperature gradient variables will be available under the puzzlingly titled "..." button for plotting on surfaces, vectors etc. aja1345 likes this.

August 15, 2016, 15:42		#11
Opaque Senior Member Join Date: Jun 2009 Posts: 1,811 Rep Power: 32	Insert an User Defined Variable, for the method select Gradient, and select Temperature for the variable. CFD-Post will create the Temperature.Gradient variable. You can then use it as needed. aja1345 likes this.

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