Hi Rob, I need to change the pressure profile within the time step because it depends on the current flowrate value through that outlet, it is a kind of 'resistance boundary condition'. I know this could seem unstable from a numerical viewpoint but hopefully, the numerical solver will converge to a certain solution after 20-30 inner iterations. In this way, it is possible to see how the pressure update on that boundary undergoes almost no changes once the solution is definetly convering (from 20th iteration on). All this can be observed in a segregated solver simulation without the usage of an overset mesh.nAnyway, I would like also to post here a picture from the iterative algorithm used on ANSYS FLUENT for both solvers, as you'll se, theoretically, DEFINE_PROFILE shall be updated every inner iteration. This is what actually makes me wonder what's happenning in there, since the same UDF code works perfectly with a segregated solver simulation.nn