PaSR: Computation of mean chemical source term
Hello All,
With the PaSR model, the mean chemical source term, Schem_mean, in the equation for the mean species, Yi_mean, is typically computed with: Schem_mean = kappa * Schem(Yi*, T*) . Here Yi_mean is just called Yi (or Y) in OF, kappa is a function which has the same name in OF, and Schem(Yi*, T*) is the chemical source term determined by (a) the chemical reaction mechanism and (b) evaluated at Yi* and T*, which are the species and temperature of fine scale burning structures. Yi* and T* can be computed from the mean values Yi_mean and T_mean through a PSR calculation (usually at constant pressure and adiabatic), which also gives Schem(Yi*, T*). The above also applies, with slight differences, to the energy equation. Now, if I understand things well, which could not be the case, what reactingFoam computes is: Schem_mean = kappa * Schem(Yi_mean, T_mean) , which is not what the PaSR model (or EDC model) is supposed to do. I came to this conclusion by examining PaSR.C and ODEChemistryModel.C. This is done either with useReactionRate true or false. Could anybody please show me why and how am I wrong? Any help will be greatly appreciated. Regards. |
Hello All,
I guess I have to answer my question myself. Strictly speaking, as explained above, the PaSR model does the following: Schem_mean = kappa * Schem(Yi*, T*) . However, users of the PaSR model (see paper below) approximate this term with Schem_mean = kappa * Schem(Yi_mean, T_mean) , which is what OF solves for. Hope this helps somebody. Regards. PS: This is the paper: Berglund, M., et al. "Finite rate chemistry large-eddy simulation of self-ignition in supersonic combustion Ramjet." AIAA journal 48.3 (2010): 540-550. |
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