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July 20, 2006, 09:52 
Could somebody tell me what ar

#1 
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Dihao Tang
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Could somebody tell me what are the values of Sutherland coefficient As and Sutherland temperature Ts for air? Thanks!


July 20, 2006, 14:04 
For viscosity:
mu=1.4584E6*p

#2 
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mbark elmorsli
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For viscosity:
mu=1.4584E6*pow(T,3./2.)/(T+110.33); and for thermal conductivity: lambda=2474.7264e6*pow(T,3./2.)/(T+194.4) 

July 26, 2006, 02:21 
Thanks for your reply. What ar

#3 
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Dihao Tang
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Thanks for your reply. What are the coefficients As and Ts for N2? Is there a table including the coefficient of all gases?


July 24, 2009, 06:29 
Where to define the conductivity?

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Tom Potters
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When using constTransport the conductivity can be calculated based on the viscosity, the heat capacity and the Prandtl number. When using sutherlandTransport there is no mention of the conductivity constant (at least not in the manual). You also give the sutherland coefficients for the conductivity, but then my question is where do I use them? Right after those of the viscosity?


October 26, 2012, 05:24 

#5 
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mohsen cheraghi
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I have the same question. can any one explain more?


October 30, 2012, 07:05 

#6 
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I am also interested in the calculation of the thermal conductivity. Is there any more information? Which numbers in the second equation are coefficients, that I have to set in OpenFOAM? Hope anyone can help us!


December 6, 2012, 08:00 

#7 
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Ehsan
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I don't think conductivity coefficients to be necessary.only As and Ts are important.


April 23, 2013, 17:37 

#8 
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Camille
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Hi,
could you tell me where I can find the sutherland coefficients As and Ts for natural gas (ie: methane). And where can I find a table of these coef. for any gas? Thank you very much 

April 3, 2014, 11:20 

#9 
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Hej everyone!
Sorry for reactivating this old post, but it is still not clear to me how the thermal conductivity is calculated by OF when using Sutherland's law. For my calculations I use chtMultiRegionSimpleFoam (OF 2.2.x) and experimented with the transport models in thermophysicalProperties of a fluid region. The thermo model I set is heRhoThermo and the fluid is air. When I set transport to "const", I define a constant dynamic viscosity mu and the Prandtl number Pr. The thermal conductivity k is then calculated by Pr=mu*cp/k. In a second example I set transport to "sutherland". Now I define only the two input parameters As=1.4792e06 and Ts=116 for Sutherland's law. Since there is no error message when starting a calculation, I guess that no other input is needed. But how does the solver calculate the thermal conductivity then? Thank you for any help, Daniel 

July 16, 2014, 16:46 

#10  
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Brock Lee
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Quote:
The OpenFOAM sutherland viscosity model appears to use the modified Euken Model (based on kinetic theory) for the thermal conductivity calculation. I found the equation being used on line 149 of the sutherlandTransportI.H file ($FOAM_SRC/thermophysicalModels/specie/transport/sutherland/sutherlandTransportI.H) I identified it as the modified Euken Model based on section 1.4.7.2.2 of this doc... http://www.arc.vt.edu/ansys_help/cfx_mod/i1299744.html Brock 

July 18, 2014, 07:00 

#11 
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Hej Brock!
Thank you very much for your precise answer! I think you are right, the solver uses the modified Eucken equation in order to calculate the thermal conductivity if the Sutherland transport model is selected. However, I am not sure how good the accuracy of this model is? From what I read, the thermal conductivity calculated from the modified Eucken equation differs up to 25% from experimental values. Anyway, the accuracy is another question. It is good to know what OpenFOAM does! Thanks again for your help! Daniel 

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