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December 4, 2012, 13:34 
how to get Sutherland and JANAF coefficients of air?

#1 
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Ehsan
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I want to use function of time values of viscosity and Cp.where can I find the proper values?


December 5, 2012, 02:45 

#2 
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Ehsan
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is there a useful document about it?i can't find anything.


December 5, 2012, 04:19 

#3 
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Did you try this?
books: https://www.google.com/search?client...w=1920&bih=968 if you are lucky you may find a free article or can access from your institution http://scholar.google.com/scholar?q=...ed=0CCwQgQMwAA 

December 5, 2012, 11:23 

#4 
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Ehsan
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Ididn't find a useful free one.


December 5, 2012, 12:08 

#5 
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Ehsan
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ofcourse I have some tables but I don't know how to use it for getting a useful numbers for importing in openfoam.another is that what componet i should use? N2 return to airis good?


December 5, 2012, 18:52 

#6 
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Ehsan
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dear friends I found the coefficients of exactly air not even nitrogen in the new format and found how to use it at old format that openfoam uses.its in openfoamwiki website but not clear.in fact a3.a4...a9 in new format are a1...a7 in old format that as i told openfoam uses.
If anyone wants the coeficients or more explanations feel free to say. 

February 22, 2013, 17:55 

#7 
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Valentin Wibaut
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I would like to have more informations about the coefficients. Can I have your thermoPhysicalProperties file? To see how you write this
If you have more explanations about this, I'm also interested. Thank you for your help 

February 23, 2013, 04:15 

#8 
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Ehsan
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hi
Ok i'll send it soon. 

February 23, 2013, 13:43 

#9 
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Ehsan
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I've set .75N2 and .25O2 and have obtain this coefficient by MATLAB.
Code:
thermoType hPsiThermo<pureMixture<sutherlandTransport<specieThermo<janafThermo<perfectGas>>>>>; mixture { specie { nMoles 1; molWeight 28.96; } thermodynamics { Tlow 200; Thigh 6000; Tcommon 1000; highCpCoeffs (3.129672277499967 1.211766752750042e3 4.04761109000018e7 6.409571300000324e11 3.780447620000211e15 1.190120342415573e3 5.2577564125); lowCpCoeffs (3.593868050000014 8.419292810001117e4 2.08457592775033e6 5.938441825004294e10 2.456771699998039e13 1.053301888245469e3 3.1400217175); /*Cp 1040; Hf 2.544e+06;*/ } transport { As 1.4584e6; Ts 110.4; /*mu 1.84e05; Pr 0.75;*/ } } 

February 24, 2013, 06:13 

#10 
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Valentin Wibaut
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Thank you very much ehsan
I have a question: why do you use N2 75% and O2 25%? Air has approximately 79% N2 and 21% O2. How do you find the coefficients with matlab? 

February 24, 2013, 07:04 

#11 
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Ehsan
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you're welcome valentin
I think i used those coefficients you said at last.i'll see the Matlab mfile and let you know about it. I wrote a mfile in matlab.you can find the coefficients of n2 and o2 in openfoamwiki,search for janaf contrib and at the page go to the link for old version of janaf. Im ready to help you more. 

February 24, 2013, 09:26 

#12 
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Valentin Wibaut
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Thanks for your help
I confirm that you use 0.75 N2 and 0.25 O2 But I have some different values and I don't find the error. I take the coefficient for O2 and N2 in the janaf table (openfoamwiki) like you. Last edited by vwibaut; February 24, 2013 at 10:23. 

February 24, 2013, 13:52 

#13 
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Valentin Wibaut
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I have an other question.
My goal is to simulate the flow in a nozzle, and I would like to take into account the variation of the cp with the temperature altough I think this variation is very small in this case. In the nozzle I can have a temperature of 120K wich is lower thant the Tlow of janaf (200K). An idea how to solve this problem? 

February 24, 2013, 14:02 

#14 
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Ehsan
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send me your values.i think it can be agreable that you extrapolate since the distance between 160 and 200 is not so high.but you should be certain that this temp is valid because some troubles in solution process may lead to very low or very high values in temperatures.


February 24, 2013, 14:43 

#15 
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Valentin Wibaut
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Yes I'm sure for the value of the temperature, it's the analytical solution Ok so I have to create a new janafthermo wich interpolate the cp when the temperature is <200K.
For the values, I don't have them here but I will let you know about it. I have the same values except for one or two. 

February 24, 2013, 19:22 

#16 
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Ehsan
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ok.im curious about the different numbers.maybe i have made a mistake.


March 8, 2013, 05:29 

#17 
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Ehsan
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could you send you calculated numbers to compare?


March 8, 2013, 05:35 

#18 
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Valentin Wibaut
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hi,
Sorry, I work in dual boot and the most of the time I can't access to matlab (and so to the coefficients you need). I will give you the coefficients as quickly as possible. 

March 11, 2013, 06:00 
my coefficients

#19 
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Valentin Wibaut
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highCpCoeffs (3.129672277499967 1.211766752750042e3 4.04761109000018e7 6.409571300000324e11 3.780447620000211e15 996.9558 5.2577564125);
lowCpCoeffs (3.593868050000014 8.419292810001117e4 2.08457592775033e6 5.938441825004294e10 2.456771699998039e13 1.0512e3 3.1400217175); It isn't a big difference 

March 13, 2013, 10:52 

#20 
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Ehsan
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how did you calculate h and s coefficients?


Tags 
janaf, openfoam, sutherland 
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