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Compressible ThermophysicalProperties for Methane

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Old   October 23, 2010, 20:48
Default Compressible ThermophysicalProperties for Methane
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Miguel Suarez
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I'm a new OpenFOAM user and also to the field of CFD. After struggling with installation and basic issues on running the tutorials, now I have questions about the ThermophysicalProperties file under the "constant" folder. Most of the tutorials have the basic thermophysicalProperties file discussed in the OpenFOAM user guide. However, i want to use compressional solvers (still undecided which is the best). The scope of the problem is quite basic: methane flowing through a duct (or pipe) with heat being applied to one side of the duct.

I need to apply an equation of state where density is a function of pressure and temperature (similar to the one used by FLUENT); however, after reading the user and programmer's guide, I was unable to come up with a solution.

My question is, how do i tell OpenFOAM that my fluid is methane and that rho(P,T)?

I found the NSRDSfunctions, but once again, i don't know how to use them in the thermophysicalproperties file... or if I even should use it.

I also found the therm.dat, but that only has coefficients for Cp and H.

Any help and guidance will be greatly appreciated.

Thank you

Miguel Suarez
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Old   October 23, 2010, 23:54
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check the user guide chapter 7.1 and good luck
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Old   October 24, 2010, 11:05
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As I mentioned before, I have read the User and Programmer's guide multiple times and have not been able to come up with an answer. I have also browsed through the threads posted in this forum, but have not found something that helps me.
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Old   November 2, 2010, 12:54
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URGENT!!!!!

I know is a simple question... but i have yet to figure it out or find somebody that can help. Using OpenFoam for a school project and would like to learn how to do this.

Once again, the issue is setting the fluid to methane (specially looking near the triple point).

All I need is an idea on how to use methane in the thermophysicalProperties file.

Thank you.

P.S. seeing the number of people that viewed my post, i know a response can help others.
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Old   November 2, 2010, 13:21
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If you are only looking at single phase flow, the easiest thing in my mind would be to use reactingFoam with the reaction chemistry turned off. I don't know if there is a tutorial in OF1.7, you can always check this out.

http://openfoamwiki.net/index.php/Tu..._firstTutorial

You would need to change the mesh, boundary conditions and initial conditions so that they match what you are studying. Specifying methane should be as simple as using the right mass fractions for the component gases and sourcing a proper chemkin file that describes methane under the conditions you wish to study.

OpenFOAM is built in a way so that implementing basic physics is as simple as selecting the right dynamic libraries. Of course, you also have the option of making your own physical models should the need arise.
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Old   November 7, 2010, 15:25
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Miguel Suarez
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Marco,

Thank you for your response. To give you a better idea, this is what i'm doing.

Using FLUENT, i modeled a channel in which methane travels through. in fluent, I used a density based solver. the material's (Methane) density was set to ideal gas. I know the equation that fluent uses. It is a 40+ term pressure equation. In other words, Pressure as a function of temperature and density. I could not find a similar equation anywhere in OpenFOAM, or how it even calculates density for air (as used in the tutorials).

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Old   November 7, 2010, 23:22
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Hi,
Specifying methane in the thermophysical properties file is quite simple. Its similar to the way the properties of air have been specified the user's guide. You just have to write the name "methane" and specify its JANAF and other properties.

As far as equation of state is concerned, its possible to specify your own equation of state. Just search the forums or google "how to add a new equation of state?". You would definitely get answers.
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