Problem with Radiation Model

[Mita Sarkar]

David,
 
Still I could not fix the problem. Please suggest me something. The case file and listing file are attached here.
 
Thanks
Mita

[David Monfort]

It seems you're trying to use the steady algorithm. We sometimes have some difficulty to make it converge with buyoancy-driven flows (it's the case here if I'm right...).
Could you try the "standard" algorithm, i.e. unsteady algorithm with a constant and uniform time-step ? Make sure to have a low-enough time-step to ensure a good convergence (i.e. CFL number below 1 or 5 at least). And you should set the listing frequency output to 1 so that we have more information on the simulation.

[Mita Sarkar]

Hi David,
 
Per your suggestion, I tried to use standard algorithm, i.e. unsteady algorithm with a constant and uniform time step (1e-05) but still solution is diverging.  Initially Courant number was small but as time goes, Courant number goes high. Here how did you calculate CFL condition/Courant number? Is it calculated as follows: CFL = (dt * Umax)/dx where dt = time step, Umax = maximum velocity and dx = element size. I tried with some more smaller time steps but it did not work yet. If you can suggest me some more trick to tackle this problem, I would appreciate your help. Is there anything else that can help me?
 
Thanks
Mita

[David Monfort]

Hi Mita,

The Courant number (and others) is computed in the dttvar subroutine. This is basically what you wrote, except that it is a bit more complex so as to take into account all kind of cells.

As for your convergence issue, I've seen Alexandre anwered to your other thread. I suggest we continue in the new one, if you don't mind.

David

[Mita Sarkar]

Hello David,
 
Thank you for your reply. It is okay, we will continue the convergence issue in the new thread.
 
Regards
Mita