Velocity profile has no sense at the inlet. This is essentially a converging-diverging nozzle and velocity should be constant before the seat valve. Moreover, based on my experience with nozzle flow, I think that the mesh should be finer in the converging-diverging zone, even though this does not explain the strange velocity profile at the inlet.
Have you tried a 2D geometry? In RANS 3D and 2D results will be the same, and in 2D a finer mesh can be obtained with a lower cell count.
EDIT: Based on the "0 bar" BC at the outlet, I guess that you are setting a operating pressure different to 0. I think that it would be a better option to set it equal to 0:
8.14.3. Setting the Operating Pressure (