TurbSim - Reference wind speed - extreme wind models (1EWM50, 1EWM1 etc.)

Hi Jason/NREL,

I created a turbulent wind field for the IEC Kaimal spectrum for a 50-year extreme wind speed of 43m/s (these values are based on meterological data for a particular site). I specified the wind type as 1EWM50 and the reference wind speed URef as 43m/s. I noticed that TurbSim ignored the input wind speed of 43m/s and used 50m/s instead. No matter what value of URef is specified, TurbSim always uses URef = 50m/s for IEWM50 wind model.

  1. Can you explain the reason for this?
  2. Can you offer any advice i.e. should I just use 1NTM or 1ETM wind models instead? This would allow me to retain my desired wind speed.

TurbSim inputs (IN file)

--------Meteorological Boundary Conditions-------------------
IECKAI TurbModel - Turbulence model (“IECKAI”,“IECVKM”,“GP_LLJ”,“NWTCUP”,“SMOOTH”,“WF_UPW”,“WF_07D”,“WF_14D”,“TIDAL”,“API”,“USRINP”,“TIMESR”, or “NONE”)
“unused” UserFile - Name of the file that contains inputs for user-defined spectra or time series inputs (used only for “USRINP” and “TIMESR” models)
“1-ED3” IECstandard - Number of IEC 61400-x standard (x=1,2, or 3 with optional 61400-1 edition number (i.e. “1-Ed2”) )
C IECturbc - IEC turbulence characteristic (“A”, “B”, “C” or the turbulence intensity in percent) (“KHTEST” option with NWTCUP model, not used for other models)
1EWM50 IEC_WindType - IEC turbulence type (“NTM”=normal, “xETM”=extreme turbulence, “xEWM1”=extreme 1-year wind, “xEWM50”=extreme 50-year wind, where x=wind turbine class 1, 2, or 3)
“default” ETMc - IEC Extreme Turbulence Model “c” parameter [m/s]
PL WindProfileType - Velocity profile type (“LOG”;“PL”=power law;“JET”;“H2L”=Log law for TIDAL model;“API”;“USR”;“TS”;“IEC”=PL on rotor disk, LOG elsewhere; or “default”)
“unused” ProfileFile - Name of the file that contains input profiles for WindProfileType=“USR” and/or TurbModel=“USRVKM” [-]
150.0 RefHt - Height of the reference velocity (URef) [m]
43 URef - Mean (total) velocity at the reference height [m/s] (or “default” for JET velocity profile) [must be 1-hr mean for API model; otherwise is the mean over AnalysisTime seconds]
“default” ZJetMax - Jet height [m] (used only for JET velocity profile, valid 70-490 m)
0.2 PLExp - Power law exponent [-] (or “default”)
0.1 Z0 - Surface roughness length [m] (or “default”)

TurbSim outputs (SUM file)
Meteorological Boundary Conditions:

IECKAI  IEC Kaimal spectral model
     1  IEC standard: IEC 61400-1 Ed. 3: 2005
     C  IEC turbulence characteristic
1EWM50  IEC Extreme 50-Year Wind Speed Model
   N/A  IEC Extreme Turbulence Model (ETM) "c" parameter [m/s]
   PL   Wind profile type

150.000 Reference height [m]
50.000 Reference wind speed [m/s]
N/A Jet height [m]
0.200 Power law exponent
0.100 Surface roughness length [m]

Dear @Aengus.Connolly,

Setting IEC_WindType = “1EWM50” in TurbSim means that the 50-year extreme wind model for wind turbine class I is to be used using the 10-minute average wind speed. The IEC does not provide flexibility on what the wind speed is for this case, so, TurbSim overrides URef with the wind speed specified in the IEC. If you want to specify your own mean hub-height wind speed, I would suggest using a different IEC_WindType, such as “NTM” as you suggest.

Best regards,

Jason - thanks for your very quick reply. This is what I was thinking myself but really appreciate your confirmation. Kind regards, Aengus.