Convergence criterion

newbie

Hi,

I'm developping a small code in order to resolve incompressible viscous bidimentionnal steady flows.

Everything seems Ok apart the convergence criterion, for now, i'm just giving the number of iteration to be sure that the code will stop.

I tried the relative convergence criterion: abs((Un+1 - Un)/Un+1)<eps but it doesn't work....

I want to apply the residual but I still don't know how. I'm working on navier-stokes equations using the primitive variable formulation.

Thanks in advance