Vorticity in sliding mesh
 

Dear all,

I am modelling an unsteady case while two rotating and stationary cavities facing each other with a specific gap and one of them is moving with velocity U paraller to the interface between these two cavities. Let's take the rotor as Upper cavity and the stator as Lower cavity. Since this case is like the rotor and stator case, sliding mesh method has been used for this simulation.

After getting a consistant periodic drag coefficient for either Lower(Stator) or Upper(Stator) wall, I have tried to see the contour of Vorticity Magnitude and surprisingly I noticed that there are significant contours of vorticity just closed to interface between two regions(Lower and Upper).

Can anyone help me what the reason is?

Thanks