question need answer, pls

happy · March 30, 2012, 05:16

Hi all
I'm using the idael gas material fro my simulation; and when I modify the air properties as function of temp., my results become the same if I used constant properties..(did not make sence)

!!!
So what you think the wrong come from???
I'm looking to hear from you soon.

Please any input can help.

Chander · March 30, 2012, 05:35

May be the temperature variation in your simulation is not significant enough to cause any change in results. So even when you use temperature dependent properties, the results are similar.
Also, I am assuming here that the properties you are referring to here are viscosity, conductivity etc and not density.

ghorrocks · March 30, 2012, 05:45

As Chander says, most people think "variable properties" is viscosity, conductivity, specific heat etc, and not density. Most people consider variable density as simply a compressible flow simulation.

And another point - in future can you use a thread name which describes the thread?

lffabiani · March 30, 2012, 07:35

Have you set the "Heat Transfer" under "Fluid Models" to "Thermal Energy"??

If it is "Isothermal", all properties will remain constant.

Best regards

happy · March 31, 2012, 00:01

Quote:

Originally Posted by Chander

May be the temperature variation in your simulation is not significant enough to cause any change in results. So even when you use temperature dependent properties, the results are similar.
Also, I am assuming here that the properties you are referring to here are viscosity, conductivity etc and not density.

yes, of course, I mean the viscosity, thermal conductivity and Cp.

happy · March 31, 2012, 00:05

Quote:

Originally Posted by lffabiani

Have you set the "Heat Transfer" under "Fluid Models" to "Thermal Energy"??

If it is "Isothermal", all properties will remain constant.

Best regards

thanks for your input, I solve the thermal energy -I did not used the isothermal.

happy · March 31, 2012, 00:08

Quote:

Originally Posted by Chander

May be the temperature variation in your simulation is not significant enough to cause any change in results. So even when you use temperature dependent properties, the results are similar.
Also, I am assuming here that the properties you are referring to here are viscosity, conductivity etc and not density.

the min. temp. is 25 C, and the max. temp. is 100 C. so I think that the devaition is large enough.

Thanks again

March 30, 2012, 05:16	question need answer, pls	#1
happy Senior Member Safia Join Date: Oct 2010 Location: Australia Posts: 161 Rep Power: 15	Hi all I'm using the idael gas material fro my simulation; and when I modify the air properties as function of temp., my results become the same if I used constant properties..(did not make sence)!!! So what you think the wrong come from??? I'm looking to hear from you soon. Please any input can help.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Is there need to use BL in 2D pipe	Salam	FLUENT	2	September 30, 2007 15:45
To red lemon pls answer	K.Baker	FLUENT	0	August 2, 2007 09:41
Who can answer me /pressure question	pam	FLUENT	7	June 23, 2007 07:50
Convergence Question	James	FLUENT	2	October 29, 2005 14:59
A simple question (Where is the answer? Not yet!!)	Mecobio	Main CFD Forum	1	February 12, 2004 07:28

March 30, 2012, 05:35		#2
Chander Senior Member Join Date: Oct 2010 Location: Zurich Posts: 176 Rep Power: 15	May be the temperature variation in your simulation is not significant enough to cause any change in results. So even when you use temperature dependent properties, the results are similar. Also, I am assuming here that the properties you are referring to here are viscosity, conductivity etc and not density.

March 30, 2012, 05:45		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	As Chander says, most people think "variable properties" is viscosity, conductivity, specific heat etc, and not density. Most people consider variable density as simply a compressible flow simulation. And another point - in future can you use a thread name which describes the thread?

March 30, 2012, 07:35		#4
lffabiani Member Luis Filipe Fabiani Join Date: Apr 2009 Posts: 43 Rep Power: 17	Have you set the "Heat Transfer" under "Fluid Models" to "Thermal Energy"?? If it is "Isothermal", all properties will remain constant. Best regards