When we start a new calculation after a few iterations it explodes. The file info sometimes writes "Warning negative energy dissipation" other times writes "inflow detected at outflow boundaries". We can 't understand where the problem could be. We think that God hate all the people who want to take the degree in this millennium!!! Seriously we think it could depend on scale factor of the model. Somebody of you has an idea to resolve our problem? And & Mir

Not sure about the negative energy problem. For inflow detected at outflow boundaries, it means that you have a boundary defined as an outlet, but fluid is coming back in. Outlet boundaries don't like inflow. Either change to a pressure boundary (which is happy with inflow or outflow) or extend your outlet farther downstream.

The warnings you get in the info file could just be temporary calculation problems. Kind of hard to answer when you don't say what your physical problem is. Maybe you should try to reduce some relaxation factors.