Inflow Turbulence Standard

The natural inflow turbulence intensity varies from 5% to 40%, I take IEC61400-1 as reference and give the intensity value as 17% ( between max value of 18% and mini value of 16% according to IEC61400-1). I wish to know how everybody give your inflow turbulence conditions when you do your windturbine CFD simulations?

I try to use the measured turbulence at 15 m/s in the target sites.
But in fact I also have your problem, and I have asked myself the same question. I believe that one should at least choose the higher between IEC and the measured one. If the wind turbine does not fall in an IEC class, then it should be “Special” class, with a given design turbulence.
Hope this helps
Best regards