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-   -   janafThermo: How to read formula? or at least: How to use hPolynomialThermo? (http://www.cfd-online.com/Forums/openfoam/72944-janafthermo-how-read-formula-least-how-use-hpolynomialthermo.html)

bgoeppner February 22, 2010 16:17

janafThermo: How to read formula? or at least: How to use hPolynomialThermo?
 
Hi everybody,

I'm simulating a nozzle with OpenFOAM. When using a constThermo-modell the simulation ends with "maximum number of iterations exeeded"-exeption for the thermodynamic model so I was thinking of using some variable heat-capacity-setting like janaf or polynoms.

But how do I have to understand the formula for the janaf-model that is given in the user-guide (http://www.openfoam.com/docs/user/th...37-2040007.1.1)?

In the biconic25-55Run35 tutorial from rhoChentralFoam there is a thermodynamic model using janaf-coefficients for N2. Unfortunately if I put those coeffs into the in user-guide provided formula for calculating heat-capacity from janaf-coeffs the function does not even behave like the experimental data (e.g. http://www.engineeringtoolbox.com/nitrogen-d_977.html)... :confused: Instead of rising with temperature the heat-capacity is lowering? The search-function didn't lead to any results...

Am I missing something? Are the coeffs in the tutorial wrong? Am I taking the wrong formula?

And by the way: How can I use the polynomial-model? In the user-guide there is only a link to a tutorial. I cannot find a word about hPolynomialThermo there (even if it obviously uses some polynoms... for heat-capacity as well as for some other vars...)

Thanks in anticipation for any suggestions or explanations!
Ben


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