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-   -   Enabling ideal gas for nitrogen (http://www.cfd-online.com/Forums/fluent/35872-enabling-ideal-gas-nitrogen.html)

manish February 26, 2005 22:49

Enabling ideal gas for nitrogen
 
Hello everyone,

How do you enable ideal gas for nitrogen?

I have donwloaded nitrogen from the database, and I have specified it as ideal gas, and Sutherland's law for viscosity. The problem I am having is that when I run the simulation, the density is ALWAYS CONSTANT!

This will definitely give me a huge error in my results. HOPEFULLY, someone has the answers.

Thank you. -Manish

manish February 26, 2005 22:57

Re: Enabling ideal gas for nitrogen
 
With the same setup and if I enable air, i see a flucutation in density. I do not know if for diatomic gases if there should be a different setting. should i set the degree of freedom...it is at zero. hope someone can help me out. thanks.

Manoj Kumar February 27, 2005 01:59

Re: Enabling ideal gas for nitrogen
 
Goto Define/Boundary Conditions and open Fluid Panel corresponding to ur Fluid Zone and set 'Material Name' as nitrogen.

Try this ...

manish February 27, 2005 02:02

Re: Enabling ideal gas for nitrogen
 
Thank you! It definitely worked. I am just trying to get it to converge.

-manish

Melaku H. March 2, 2005 05:56

Re: Enabling ideal gas for nitrogen
 
Hi,

Yeah that is a little bug I guess. The ppl at Fluent need to fix it...one doesn't have to set matrial properties twice! Pls make sure the operating pressure is ok too. If you have a closed domain you probably need to activate floating operating pressure inorder to get a reasonable convergence.

good luck

Melaku H.

manish March 2, 2005 09:04

Re: Enabling ideal gas for nitrogen
 
I just have a jet impinging on a plate...do I need to have a floating operating pressure for this. I set my operating pressure as the standard chamber atmosphere, and I set my boundary conditions accordingly. Is this okay? I was told it was.

hope to hear from someone soon. thanks.

-manish

Melaku H. March 2, 2005 12:46

Re: Enabling ideal gas for nitrogen
 
Hi,

My answer would be a NO! It appears to me that you have external flow at hand and if there is no change in the level of absolute pressure(not guage) and the simulation is steady....I don't think any reason to have floating operating pressure. It is used when you usually have a closed domain or open at one end only...e.g filling of a pressure tank.

rgds

Melaku H


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