Fatigue Load of a 5MW Baseline Under Yaw Offset

I conducted fatigue load simulations by generating 6 wind speed seeds and 10-minute wind fields for the mean hub-height wind speed according to design load case 1.2 of IEC 61400. The wind field has a mean wind speed width of 2 m/s. The wind speeds, ranging from 6 m/s to 14 m/s, generated the wind field using TurbSim. The shear exponent is 0.2, surface roughness is 0.03, and TI is class A. The time series data of each run were utilized to compute the fatigue DEL experienced by the wind turbine at yaw offsets ranging from -40 degrees to 40 degrees. For an NTM, turbulence intensity class A is used for the entire wind speed bins, and dynamic blade element momentum theory was applied for the entire simulation. However, the discrepancies between the simulated and reference results for OOP and combined tower moment (tower base My and Mx) are much higher.

Q1). What changes can I make to minimize the inaccuracy of my simulation results to better fit the reference results?

Best regards,

---------TurbSim v2.* Input File------------------------
Example file that can be used with simulations for the NREL 5MW Baseline Turbine; note that UsableTime has been decreased in this file so that the file distributed with the FAST CertTest isn't as large
---------Runtime Options-----------------------------------
False         Echo            - Echo input data to <RootName>.ech (flag)
      6695654   RandSeed1       - First random seed  (-2147483648 to 2147483647)
"RanLux"      RandSeed2       - Second random seed (-2147483648 to 2147483647) for intrinsic pRNG, or an alternative pRNG: "RanLux" or "RNSNLW"
False         WrBHHTP         - Output hub-height turbulence parameters in binary form?  (Generates RootName.bin)
False         WrFHHTP         - Output hub-height turbulence parameters in formatted form?  (Generates RootName.dat)
False         WrADHH          - Output hub-height time-series data in AeroDyn form?  (Generates RootName.hh)
True          WrADFF          - Output full-field time-series data in TurbSim/AeroDyn form? (Generates RootName.bts)
False         WrBLFF          - Output full-field time-series data in BLADED/AeroDyn form?  (Generates RootName.wnd)
False          WrADTWR         - Output tower time-series data? (Generates RootName.twr)
False         WrHAWCFF        - Output full-field time-series data in HAWC form?  (Generates RootName-u.bin, RootName-v.bin, RootName-w.bin, RootName.hawc)
False         WrFMTFF         - Output full-field time-series data in formatted (readable) form?  (Generates RootName.u, RootName.v, RootName.w)
False         WrACT           - Output coherent turbulence time steps in AeroDyn form? (Generates RootName.cts)
          0   ScaleIEC        - Scale IEC turbulence models to exact target standard deviation? [0=no additional scaling; 1=use hub scale uniformly; 2=use individual scales]

--------Turbine/Model Specifications-----------------------
         31   NumGrid_Z       - Vertical grid-point matrix dimension
         31   NumGrid_Y       - Horizontal grid-point matrix dimension
       0.02   TimeStep        - Time step [seconds]
        600   AnalysisTime    - Length of analysis time series [seconds] (program will add time if necessary: AnalysisTime = MAX(AnalysisTime, UsableTime+GridWidth/MeanHHWS) )
        "ALL"   UsableTime      - Usable length of output time series [seconds] (program will add GridWidth/MeanHHWS seconds unless UsableTime is "ALL")
         90   HubHt           - Hub height [m] (should be > 0.5*GridHeight)
        175   GridHeight      - Grid height [m]
        175   GridWidth       - Grid width [m] (should be >= 2*(RotorRadius+ShaftLength))
          0   VFlowAng        - Vertical mean flow (uptilt) angle [degrees]
          0   HFlowAng        - Horizontal mean flow (skew) angle [degrees]

--------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")
"TurbSim_User.spectra"    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") )
"A"          IECturbc        - IEC turbulence characteristic ("A", "B", "C" or the turbulence intensity in percent) ("KHTEST" option with NWTCUP model, not used for other models)
"NTM"         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")
"TurbSim_User.profiles"    ProfileFile     - Name of the file that contains input profiles for WindProfileType="USR" and/or TurbModel="USRVKM" [-]
         90   RefHt           - Height of the reference velocity (URef) [m]
         14   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")
"default"     Z0              - Surface roughness length [m] (or "default")

--------Non-IEC Meteorological Boundary Conditions------------
"default"     Latitude        - Site latitude [degrees] (or "default")
       0.05   RICH_NO         - Gradient Richardson number [-]
"default"     UStar           - Friction or shear velocity [m/s] (or "default")
"default"     ZI              - Mixing layer depth [m] (or "default")
"default"     PC_UW           - Hub mean u'w' Reynolds stress [m^2/s^2] (or "default" or "none")
"default"     PC_UV           - Hub mean u'v' Reynolds stress [m^2/s^2] (or "default" or "none")
"default"     PC_VW           - Hub mean v'w' Reynolds stress [m^2/s^2] (or "default" or "none")

--------Spatial Coherence Parameters----------------------------
"default"     SCMod1          - u-component coherence model ("GENERAL","IEC","API","NONE", or "default")
"default"     SCMod2          - v-component coherence model ("GENERAL","IEC","NONE", or "default")
"default"     SCMod3          - w-component coherence model ("GENERAL","IEC","NONE", or "default")
"default"     InCDec1         - u-component coherence parameters for general or IEC models [-, m^-1] (e.g. "10.0  0.3e-3" in quotes) (or "default")
"default"     InCDec2         - v-component coherence parameters for general or IEC models [-, m^-1] (e.g. "10.0  0.3e-3" in quotes) (or "default")
"default"     InCDec3         - w-component coherence parameters for general or IEC models [-, m^-1] (e.g. "10.0  0.3e-3" in quotes) (or "default")
"default"     CohExp          - Coherence exponent for general model [-] (or "default")

--------Coherent Turbulence Scaling Parameters-------------------
"M:\coh_events\eventdata"    CTEventPath     - Name of the path where event data files are located
"Random"      CTEventFile     - Type of event files ("LES", "DNS", or "RANDOM")
true          Randomize       - Randomize the disturbance scale and locations? (true/false)
          1   DistScl         - Disturbance scale [-] (ratio of event dataset height to rotor disk). (Ignored when Randomize = true.)
        0.5   CTLy            - Fractional location of tower centerline from right [-] (looking downwind) to left side of the dataset. (Ignored when Randomize = true.)
        0.5   CTLz            - Fractional location of hub height from the bottom of the dataset. [-] (Ignored when Randomize = true.)
         10   CTStartTime     - Minimum start time for coherent structures in RootName.cts [seconds]

! NOTE: Do not add or remove any lines in this file!

Hi Dereje,

For some context, I think your reference is from a conference paper of mine several years ago. That study used FAST7, I believe, and I would have to look hard to find the exact aero/structural (and control) parameters.

These models are also updated over time, so it may be difficult to obtain a match better than you already have. For another reference, you might try and qualitatively match the trends of field experiments in this study: WES - Assessment of wind turbine component loads under yaw-offset conditions

I haven’t looked at yaw loads much since this study, so perhaps others have some guidance to match the trends you seek.

Best, Dan

Dear @Daniel.Zalkind,

Thank you for your time and guidance. I’ll use the reference that you’ve mentioned.

Best regards,