# how to get Sutherland and JANAF coefficients of air?

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 March 13, 2013, 11:04 #21 Member   Valentin Wibaut Join Date: Oct 2012 Posts: 45 Rep Power: 6 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

 March 13, 2013, 11:16 #22 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,209 Rep Power: 19 but why they're a little different.there is not air for old version of janaf that OF uses.

 March 19, 2013, 10:33 #23 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,209 Rep Power: 19 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?

 March 27, 2013, 20:55 #24 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,209 Rep Power: 19 do you know the keyword for puting Cp's in each time step to see in paraView?(like the command Mach for mach number

 March 28, 2013, 02:59 #25 Member   Valentin Wibaut Join Date: Oct 2012 Posts: 45 Rep Power: 6 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.

 April 25, 2013, 10:37 #26 Member   Join Date: Nov 2012 Posts: 67 Rep Power: 5 is it possible to calculate the janaf coeffs for temperture below 30 K for air? immortality likes this.

 June 23, 2013, 13:01 #27 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,209 Rep Power: 19 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. __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

 November 18, 2013, 16:57 Source for data #28 Senior Member   Bernhard Linseisen Join Date: May 2010 Location: Magdeburg/Geneva Posts: 180 Blog Entries: 1 Rep Power: 8 1.) Concerning reliable data, you can also ask goolge for "NIST 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... immortality likes this.

 December 20, 2013, 18:44 #29 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,209 Rep Power: 19 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. __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

 April 18, 2016, 07:59 #30 Member   AdOo Join Date: Mar 2016 Location: Bordeaux Posts: 91 Rep Power: 2 Hi immortality, Do you manage to use the Janaf Coefficient ? I would like to use them for my simulation, but I'm wondering about the units used in OpenFOAM in oder to adapt the coefficient I've found. Do you know the units used in OpenFOAM ? Because that's really a mess... between J, cal or mol,kg... pfff I'm a bit lost from on source to another. To be sure of what I do, I need to know what OpenFoam is working with.

 Tags janaf, openfoam, sutherland

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