specify the turbulence intensity and the turbulence length
 

Hi All
I have a lag of knowledge regarding how to specify the turbulence intensity and the turbulence length for valve in given situations. I am trying to replicate some physical test data in CFD simulation.
I have tried all sorts of variations on the mesh, internal surface roughness, turbulence intensity from 2 to 20% and turbulence length form 0,002 to 1 m, the larger the turbulence length the closer the result but still far off.
In the physical world the test results where
DN 80 manual balancing valve KV at 12mm opening and there the opening ring cross section perpendicular to the flow direction is app.322,16 mm²
nominal flow velocity in the pipe of 4 m/s

Flow measured in test:
14,83 m³/h.

Fluent simulation. Same situation
16,75 m³/h

Simulation flow 2012, Same situation
20,68 -19,11 m³/h dependent on mesh turbulence settings.

Is this really how close I can expect to get.

Thank you for your help.
Best Regards
Bennoman75