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how to get Sutherland and JANAF coefficients of air?

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Old   March 13, 2013, 11:04
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Valentin Wibaut
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I use the values in the janaf file and make as you tell. (coeff = coeff N2 * 0.75 + coeff02 * 0.25)
Just a remark, I think that there is AIR in the janaf file so you haven't to calculate the coefficients
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Old   March 13, 2013, 11:16
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but why they're a little different.there is not air for old version of janaf that OF uses.
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Old   March 19, 2013, 10:33
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yes.your question caused my mistake to be corrected.
then to store for future users the correct coefficients for air in JANAF old version(7-coefficients that OpenFOAM uses) are:
Code:
thermodynamics
    {
     Tlow 200;
     Thigh 6000;
     Tcommon 1000;
     highCpCoeffs (3.129672277499967 1.211766752750042e-3 -4.04761109000018e-7 6.409571300000324e-11 -3.780447620000211e-15 -.996955811e3 5.257756413);
     lowCpCoeffs  (3.593868050000014 -8.419292810001117e-4 2.08457592775033e-6 -5.938441825004294e-10 -2.456771699998039e-13 -1.0512181e3 3.140021718);
        /*Cp              1040;
        Hf              2.544e+06;*/
    }
did you find direct coefficients for 7-coefficient format for air in JANAF?
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Old   March 27, 2013, 20:55
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do you know the keyword for puting Cp's in each time step to see in paraView?(like the command Mach for mach number
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Old   March 28, 2013, 02:59
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No I don't know any keyword to do that. I don't use the janaf coefficients because the temperatures of my application are out of the range of temperatures possible with janaf.
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Old   April 25, 2013, 10:37
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is it possible to calculate the janaf coeffs for temperture below 30 K for air?
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Old   June 23, 2013, 13:01
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Its a very low temperature.I think maybe the gas not can be considered perfect in this low temperature.
when we use Cp(T) and Cv(T) the gas is assumed be perfect gas.are you pressures very low too?
you maybe need to use real gas equations of state.
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Old   November 18, 2013, 16:57
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1.) Concerning reliable data, you can also ask goolge for "NIST <gas needed> thermodynamic properties". Then you quite quickly should find some data for different gases, among others air.
From these you should be able to calculate the coefficients with octave or matlab. I am still digging in the code what would be the right way of including the coefficients (they have to be modified with some factor)...

2.) Air below 30K will be quite challenging, aside from that being non-physical most probably. According to some NIST-information, air seems to become solid around 60 K. Thus you will not only be in the liquid phase but in a solid phase...
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Old   December 20, 2013, 18:44
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Hi all,
the link for JANAF table in here:http://openfoamwiki.net/index.php/Janaf seems have been broken.does anybody know another link for old version like that?
thanks.
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