Transport model

adrieno · April 7, 2016, 09:09

Hi all,

I'm facing with the eternal problem of transport model...
I said "eternal" because before posting this thread, I was looking on many older posts which has been unsolved for years now.

Like most of the older post, I was initially looking for some As and Ts coefficient, in order to run reactingFoam (without reaction) using the Sutherland model (used in the counterFlowFlame2D OpenFOAM exemple).

The thing is:

As I said, it is very difficult to find liable values (even just values...)
This Transport properties model, based on modified Euken model seems not to be very accuracy.

So concretely, how do you prepare your Transport model for your simulation ?

Do you manage to find the Sutherland coefficient and temperature you need for your case ?
Do you use the polynomial model ? (but here again, there's the question on how to find the required coefficient... I can't see the light at the end of the tunnel)
Do you program your own Transport model ? (I'm freaking out, you're telling me that's how you do)
Do you simply use the const model whithout tempting to surch any coefficient... ? (I'm sure you worth better than this one)

Thank you for your replies,
Adrien

adrieno · April 7, 2016, 12:18

According https://openfoamwiki.net/index.php/Contrib/Janaf :

" In OpenFOAM the same reader, which reads the thermodynamic data of the janaf table also contains the input data of the laminar viscosity. Therefor the Sutherland formula is used, which shows a linear increasing of the viscosity depending on the temperature. The input data is hard coded and describes the temperature dependent viscosity of pure nitrogen. In a case with nitrogen as environmental gas this could be an acceptable approximation, if there are no ionization processes. "

and

" For temperatures above 10000 K the Sutherland formula is not a good approximation anymore. The beginning ionization leads to an decreasing of the laminar viscostiy. Therefor a transport model based on polynomials should be used instead. "

The question of the ability to find the Sutherland coefficients and temperatures is then still topical for those who trust on this model.

April 7, 2016, 09:09	Transport model	#1
adrieno Member AdOo Join Date: Mar 2016 Location: Bordeaux Posts: 91 Rep Power: 10	Hi all, I'm facing with the eternal problem of transport model... I said "eternal" because before posting this thread, I was looking on many older posts which has been unsolved for years now. Like most of the older post, I was initially looking for some As and Ts coefficient, in order to run reactingFoam (without reaction) using the Sutherland model (used in the counterFlowFlame2D OpenFOAM exemple). The thing is: As I said, it is very difficult to find liable values (even just values...) This Transport properties model, based on modified Euken model seems not to be very accuracy. So concretely, how do you prepare your Transport model for your simulation ? Do you manage to find the Sutherland coefficient and temperature you need for your case ? Do you use the polynomial model ? (but here again, there's the question on how to find the required coefficient... I can't see the light at the end of the tunnel) Do you program your own Transport model ? (I'm freaking out, you're telling me that's how you do) Do you simply use the const model whithout tempting to surch any coefficient... ? (I'm sure you worth better than this one) Thank you for your replies, Adrien

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April 7, 2016, 12:18		#2
adrieno Member AdOo Join Date: Mar 2016 Location: Bordeaux Posts: 91 Rep Power: 10	According https://openfoamwiki.net/index.php/Contrib/Janaf : " In OpenFOAM the same reader, which reads the thermodynamic data of the janaf table also contains the input data of the laminar viscosity. Therefor the Sutherland formula is used, which shows a linear increasing of the viscosity depending on the temperature. The input data is hard coded and describes the temperature dependent viscosity of pure nitrogen. In a case with nitrogen as environmental gas this could be an acceptable approximation, if there are no ionization processes. " and " For temperatures above 10000 K the Sutherland formula is not a good approximation anymore. The beginning ionization leads to an decreasing of the laminar viscostiy. Therefor a transport model based on polynomials should be used instead. " The question of the ability to find the Sutherland coefficients and temperatures is then still topical for those who trust on this model.