epsilon as implicit term in kEqn's
I have remarked that in several turbulence models where the turbulent kinetic energy is solved, the dissipation term appears as:
Code:
- fvm::Sp(alpha*rho*epsilon_/k_, k_) and I was wondering the reason behind this piece of code. żDoes it give some stability? As far as I see, if all the left input is constant, it means that the contribution of epsilon on the equation will be affected by the factor k_calculated/k. ĦThank you for your answers! |
So, do you think this is the best way to introduce the dissipation rates on turbulence models?
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Yes. Indeed, I think it is the only way to do it without risking instability.
Okay, well strictly speaking if you have other Su source terms with positive coefficients you could try implement a scheme where you put part of the dissipation term in Su (making sure that Su stayed positive) and put the rest in Sp ... but I don't see any benefit from doing that, and it's certainly a lot of work. |
What disturbs me in this approach is that in the k equation you should the dissipation term as , where the k on the numerator changes as solving the equation. It means that in certain regions this dissipation term might be larger than the existing epsilon value (as it is multiplied by a factor ).
This method helps to ensure stability but I find it not so physical because of this factor. |
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Quote:
Indeed, specially when running steady state simulations as me... I had a look on Patankar's book and I found what you meant about the source terms... I will revise my implementations! I actually had some other divergence problems, and they might be caused by this... Thank you! |
My pleasure! Glad to be of help.
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