Add a stop criteria for an unsteady multiphase simulation
 

Dear all
I'm working on a multiphase problem on twoPhaseEulerFoam on an air-water separator.
My problem become steady from a moment but i have to make a simulation process whe the piece can change.
So i don't know how to stop my simulation on the optimal iteration when she becomes steady.
I would like make a stop criteria on the average velocity on a patch if possible.
Do i have to use a writeAndEndSwakExpression? (i use OpenFoam 4x and swak4foam is not stable on this version)
I saw that we can use that function to look about the delta between the value of a probe at time t and the value of the same probe at time (t-dt). And when this delta become smaller than a fixed value, we can make than simulation stop.
This trick is possible on openfoam classic and for a patch instead of an probe?

I also tried using the tolerance in fvsolution but i don't understand all specificity. Are all tolerances need to be verify to stop the simulation? I tried to make all tolerance on a big value but that doesn't stop.

Thank you very much for your answers and have a good day!

Ps: Sorry for my bad english