divergence in AMG solver
 

hey all,

I am trying to model flow through porous media in fluent but when I iterate I get the followng error message:

"Error: Internal error at line 842 in file 'rp_mstage.c'. divergence detected in AMG solver Error Object: ()"

Can anyone explain the meaning of this and suggest what I should do to resolve it?

Best, Louisa

Re: divergence in AMG solver
 

It basically means that your model is numerically unstable.

Have you tried solving the flow field without the porous zone activated and then switching it on later when the solution has converged somewhat?

Also, double check the values that you've used for the viscous and inertial resistance coefficients to make sure that they are realistic.

Re: divergence in AMG solver
 

in addition to what Tim said, ur Mesh type also plays an important rule....what kind of mesh r u using for porous zone?

Re: divergence in AMG solver
 

I had this message once and worked through it changing the Courant number as well as initial guessing in the solution initialization panel, if you are using coupled solution try changing the Courant number if not try the other way...

Re: divergence in AMG solver
 

thanks so much aimara.. yes im using coupled equations-i found out about the courant number a few days ago and i am so excited you said just now that your problem was solved changing the c. number as well.. i was just going to make a new post asking if it is sufficient to just change the courant number to overcome this problem!

do you know y fluent has as default courant number 5 whereas the courant number can have values between 0 and 1, though?

Louisa

Re: divergence in AMG solver
 

You can use a lower Courant number (CFL) for the initial iterations when changes in the solution are highly nonlinear...and then you can increase it....

Regards

Re: divergence in AMG solver
 

thanks a lot!