[su_junwei]

Hi
The variable of convergenceCriterion was defined in initConvergenceCheck.H in simpleFoam solver. The default is zero,and thus the solver will not stop. You can just add a new entry in simple dictionary of fvSolution like following
SIMPLE
{
nNonOrthogonalCorrectors 0;
pRefCell 0;
pRefValue 0;
convergence 1e-6;
}
If the initial residual for all the equations are lower than 1e-6, the simulation stops.

regards, Junwei