[Techies]

Hi guys,
I'm simulating the air through cylinders relating heat transfer
But I have a problem. Contour velocity in the last row (following the air) have strange distribution. The tail of eddy is so long and I don't understand why, even it can extend to the outlet. It sames the reverse flow. I tried to mesh the dowstream but it still happens. I don't have Temperature outlet,, so I can't' use the Opening Boundary to prevent Reverse Flow.
The second question is near the side of geometry, the velocity increase begining the third row, I don't know what is this. My side wall is symmetry.
I hope u can explain me why and what the phenomenon is.
Thanks all