open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,

I know that if the error information 'EXCEEDING MAXIMUM ITERATIONS' shows, It's the real COURANT NUMBER culculated through C = u*∆t/∆x is bigger than desired.

But my situation is different. It's stoped at neap tidal after spring tidal. Wihch means that 'EXCEEDING MAXIMUM ITERATIONS' happened at a relatively smaller velocity.

Yes, I will reduce my Timestep, But is anyone know why is it happened? Thanks in advance.

Regards,
Bin

Hello

This warning message is linked to the Courant number but not always with this expression and not in the same manner with all schemes.
This warning appears simply when the linear solver does not reach the wanted accuracy within the maximum number of iterations given by the user (or set by default). The final linear system inlcludes the advection part but also the elliptic part and even source terms (or part of them).

The smartest way to do is:
1- to increase the maximum number of iterations for the solver
2- decrease the time step
3- if you are not severe with your quality you can decrease the accuracy of the solver

In some times also you can try to play with the preconditioners.

These are the numerical tools and reasons for the appearance of this warning. But you have to keep in mind that these numerical conditions come from physical reasons also. When you start with an initial condition which is far from real physics (cold start for instance) you can have this kind of error. when you are forcing the model with very brutal forces, you can also have such message etc.

I hope this helps

With my best regards

Riadh

Hi Riadh,

Thank you so much for your detailed explanation.

Best Regards,
Bin