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-   -   how to get Sutherland and JANAF coefficients of air? (http://www.cfd-online.com/Forums/openfoam-solving/110139-how-get-sutherland-janaf-coefficients-air.html)

immortality December 4, 2012 13:34

how to get Sutherland and JANAF coefficients of air?
 
I want to use function of time values of viscosity and Cp.where can I find the proper values?

immortality December 5, 2012 02:45

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

Hanzo December 5, 2012 04:19

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

immortality December 5, 2012 11:23

Ididn't find a useful free one.

immortality December 5, 2012 12:08

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?

immortality December 5, 2012 18:52

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.

vwibaut February 22, 2013 17:55

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 :)

immortality February 23, 2013 04:15

hi
Ok i'll send it soon.

immortality February 23, 2013 13:43

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 1.211766752750042e-3 -4.04761109000018e-7 6.409571300000324e-11 -3.780447620000211e-15 -1.190120342415573e3 5.2577564125);
    lowCpCoeffs  (3.593868050000014 -8.419292810001117e-4 2.08457592775033e-6 -5.938441825004294e-10 -2.456771699998039e-13 -1.053301888245469e3 3.1400217175);
        /*Cp              1040;
        Hf              2.544e+06;*/
    }
    transport
    {
      As 1.4584e-6;
      Ts 110.4;
        /*mu              1.84e-05;
        Pr              0.75;*/
    }
}


vwibaut February 24, 2013 06:13

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?

immortality February 24, 2013 07:04

you're welcome valentin;)
I think i used those coefficients you said at last.i'll see the Matlab m-file and let you know about it.
I wrote a m-file 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.

vwibaut February 24, 2013 09:26

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.

vwibaut February 24, 2013 13:52

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?

immortality February 24, 2013 14:02

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.

vwibaut February 24, 2013 14:43

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.

immortality February 24, 2013 19:22

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

immortality March 8, 2013 05:29

could you send you calculated numbers to compare?

vwibaut March 8, 2013 05:35

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.

vwibaut March 11, 2013 06:00

my coefficients
 
highCpCoeffs (3.129672277499967 1.211766752750042e-3 -4.04761109000018e-7 6.409571300000324e-11 -3.780447620000211e-15 -996.9558 5.2577564125);
lowCpCoeffs (3.593868050000014 -8.419292810001117e-4 2.08457592775033e-6 -5.938441825004294e-10 -2.456771699998039e-13 -1.0512e3 3.1400217175);

It isn't a big difference :)

immortality March 13, 2013 10:52

how did you calculate h and s coefficients?


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