Hi, and thanks for using the forum!
I checked your model, and there are a few aspects to improve in the CAD. Here are my suggestions:
- The volume of the blades needs to be removed from the flow region. I tried to do it, but there is an error due to gaps. Fix this by merging the blades with the hub and a boolean operation.
- The volume for the rotating region needs to be immersed in the flow region, and even leave a gap to the walls. I think the problem is the void in the shaft region. You can remove the shaft model, or change the flow region geometry to comply with the conditions above.
- I would recommend to also try with the Standard mesher besides the Hex-dominant.