I have been trying to simulate a two stages turbine on SolidWorks flow simulation. It was working fine while I have some space between the turbine blades and the casing. Now, I have tried to tighten the space water has to flow so that it interacts more with the turbine blades.

There is one issue though: I get an error of "single flow condition in the closed subdomain". I suppose it is because I have not left any space for water to flow to the outlet, since I am forcing it to push the blades...

I have not defined a rotating region, since I want water to push the blades and not the other way around (am I wrong about this?).

How can I configure the simulation to explicitly tell Solidworks water is going to flow to the outlet since the openings will be created when the blades move? Can can I build an internal flow simulation with blades like this? Is there any reference I can use? Thank you.

This image shows my simulation from before: Most of the water is flowing between the rotors, and not pushing their blades (the casing is hidden for visualization, but is between both rotors). I have then tighten the space between the casing and the blades so that no water can flow there.
oldSimulation.jpg