WAT 3.0 - importing reference turbulence data

[yia179]

Dear WAsP Team,

I am trying to calculate the effective turbulence using measured data for the representative ambient turbulence at every WTG position and hub height (exported from CFD) in WAT 3.0.
The problem is that the program makes some extrapolations and the ambient representative turbulence that I observe after importing the data is not the same with the one considered for the wake calculation.
Is there a way that WAT considers only the raw data TI without any extrapolation?

Thanks a lot!

[Morten]

First of all, please note that the representative TI defined by the IEC standard is the 90% percentile of all observations including natural variation induced by variable atmospheric stability and unsteady wind speed. Thus representative TI is higher than mean TI. To model this effect, your CFD model needs to both model the mean TI and the standard deviation of the TI. WAT will then model the 90% percentile as Mean(TI) + 1.28 x StDev(TI) at each wind speed and direction.


WAT makes a distinction between observed and TI statistics, modelled by e.g. a CFD model. Modelled TI statistics is added for each turbine site from the WAT main menu. Observed TI statistics is added to a TI reference mast and the deviation of the WEng TI predictions at the TI reference mast is used to correct the WEng estimates at the turbine sites. Normally you don't have observations at all wind speeds, and this is why WAT applies an extrapolation for high wind speeds. You could make this extrapolation yourself, and import the corrected statistics.