Iteration Errors

Vidya Raja

Hi,

I have to run a case with laminar unsteady flow. I wrote the UDF that describes the unsteady velocity profile, hooked it up to Fluent. But the simulation seems to be outrageously slow. I even changed to second order upwinding, reduced the relaxation factors. Even then, there's no improvement.

After about 151 iterations (my time step size is 0.01 with 400 time steps), I get an error mesage that says:

Error: divergence detected in AMG solver: y- momentum

Error Object )

What does this mean and how can it be corrected?

Any opinions/ suggestions?

Thanks, Vidya