Prism layer advice needed for steady state port flow case
 

Please share your insight on how to properly design prism layer strategy for steady state port flow case. Inlet/Outlet pressure differential is 6975 Pa. I'm using a realizable k-e turbulence model. The geometry is a 4-valve per cylinder (2 intake / 2 exhaust) intake port. The geometry is symmetrical so I am only modeling one half of the geometry. Intake valve OD is 37 mm. valve lift is 14 mm.

My questions are:

1. How can I determine desirable thickness of prism layer? Should thickness be a Percentage or Absolute?
2. How many layers should there be?
3. How should they be scaled/stretched?
4. How can I determine what my Y+ values should be?

Any advice you can offer would be greatly appreciated. Thank you

Somebody throw me a bone!