discontinuity
 

Sorry I just realized that the image was not from you. Thanks for your reply. What do you mean by "usually" there is a boundary condition. Should I specify a particular condition at this interface so the flow of the rotating region blends smoothly with the free fluid?

Ups, sorry "usually" was not the right word. The Rotating Reference Frame RRF approach is based on a region you define in which you basically spin the fluid around the rotor instead of spinning the rotor. For that of course this region is calculated seperately compared to the rest of the fluid volume but needs a boundary condition (BC) between the outer region and the inner region of the RRF. Hence there is a (in FloEFD) hidden BC which the user does not have to apply manually, it is done automatically when applying the RRF BC. Such a BC can cause diffusion of the flow values. How strong they are and can be seen in the plots can of course depend on how fine the mesh is. Since I have no idea of how the mesh of this model looks like I cannot tell if this is the reason.
You can test it yourselfe by using one of the tutorials that applies the RRF approach.

Boris

Rrf
 

Thank you very much for your time Boris. I'll go check those tutorials.

Louis