I am using FLUENT to model an axi-symmetric impinging jet. I am using constant pressure boundaries at the top and on the far right. A wall at the bottom, a axi-symmetric boundary on the left and an inlet a the top. Everything runs fine but my results (including the centre line velocity) especially the axial velocity are far too low as I approach the plate. I have a plate to inlet spacing of 2d. The problems seem to start happening 1d from the plate.

That is normal behaviour, as the flow approaches the solid boundary a stagnation area is formed. Plot the total pressure, that will make things clear to you good luck with your simulation

Thanks for the reply. Yes I expected the flow to slow down but it is reducing much more than the experiments. I was trying to think why it may be reducing much more than expected.

1- How does your results compare to those published by Schlichting (Boundary layer theory, page 100 Seventh Edition) keeping in mind that his solution is for a laminar flow 2- Do you observe any change in the results with changing the mesh distribution inside the stagnation area