Fast errors for extreme load cases

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Patrick.Lai
Posts: 7
Joined: Mon Sep 07, 2020 6:52 am
Organization: Hongkong University of science and technology
Location: Hongkong

Fast errors for extreme load cases

Postby Patrick.Lai » Thu Apr 08, 2021 8:05 pm

Dear all,

I am currently using FAST v7 to model the response of NREL 5MW offshore wind turbine under special extreme cases, in which the turbine is loss of network (idling) and the yaw and pitch systems both are out of control. The possible yaw misalignment and pitch angles are ±180° and 0-90°,respectively. The wind and wave parameters are: U=40m/s, TI=11%, Hs=8m, Tp=11s. The settings related to the yaw and pitch system in the main input files are following Dr. Jonkman’s recommendations in other forum topics.

When I run these simulations, I got the following error for the cases where pitch angle=0 (other cases, i.e. pitch angle>0, run normally). I really appreciate it if someone could help me to solve this problem. The main input file for yaw angle=60, pitch angle=0 is attached for your further check.

Best regards,
Patrick


Code: Select all

--------------------------------------------------------------------------------
------- FAST INPUT FILE --------------------------------------------------------
NREL 5.0 MW Baseline Wind Turbine for Use in Offshore Analysis.
Properties from Dutch Offshore Wind Energy Converter (DOWEC) 6MW Pre-Design (10046_009.pdf) and REpower 5M 5MW (5m_uk.pdf); Compatible with FAST v7.0.
---------------------- SIMULATION CONTROL --------------------------------------
False       Echo        - Echo input data to "echo.out" (flag)
   1        ADAMSPrep   - ADAMS preprocessor mode {1: Run FAST, 2: use FAST as a preprocessor to create an ADAMS model, 3: do both} (switch)
   1        AnalMode    - Analysis mode {1: Run a time-marching simulation, 2: create a periodic linearized model} (switch)
   3        NumBl       - Number of blades (-)
   630.0      TMax        - Total run time (s)
   0.001    DT          - Integration time step (s)
---------------------- TURBINE CONTROL -----------------------------------------
   0        YCMode      - Yaw control mode {0: none, 1: user-defined from routine UserYawCont, 2: user-defined from Simulink} (switch)
9999.9      TYCOn       - Time to enable active yaw control (s) [unused when YCMode=0]
   0        PCMode      - Pitch control mode {0: none, 1: user-defined from routine PitchCntrl, 2: user-defined from Simulink} (switch)
   0.0      TPCOn       - Time to enable active pitch control (s) [unused when PCMode=0]
   2        VSContrl    - Variable-speed control mode {0: none, 1: simple VS, 2: user-defined from routine UserVSCont, 3: user-defined from Simulink} (switch)
9999.9      VS_RtGnSp   - Rated generator speed for simple variable-speed generator control (HSS side) (rpm) [used only when VSContrl=1]
9999.9      VS_RtTq     - Rated generator torque/constant generator torque in Region 3 for simple variable-speed generator control (HSS side) (N-m) [used only when VSContrl=1]
9999.9      VS_Rgn2K    - Generator torque constant in Region 2 for simple variable-speed generator control (HSS side) (N-m/rpm^2) [used only when VSContrl=1]
9999.9      VS_SlPc     - Rated generator slip percentage in Region 2 1/2 for simple variable-speed generator control (%) [used only when VSContrl=1]
   2        GenModel    - Generator model {1: simple, 2: Thevenin, 3: user-defined from routine UserGen} (switch) [used only when VSContrl=0]
True        GenTiStr    - Method to start the generator {T: timed using TimGenOn, F: generator speed using SpdGenOn} (flag)
True        GenTiStp    - Method to stop the generator {T: timed using TimGenOf, F: when generator power = 0} (flag)
9999.9      SpdGenOn    - Generator speed to turn on the generator for a startup (HSS speed) (rpm) [used only when GenTiStr=False]
9999.9      TimGenOn    - Time to turn on the generator for a startup (s) [used only when GenTiStr=True]
9999.9      TimGenOf    - Time to turn off the generator (s) [used only when GenTiStp=True]
   1        HSSBrMode   - HSS brake model {1: simple, 2: user-defined from routine UserHSSBr} (switch)
9999.9      THSSBrDp    - Time to initiate deployment of the HSS brake (s)
9999.9      TiDynBrk    - Time to initiate deployment of the dynamic generator brake [CURRENTLY IGNORED] (s)
9999.9      TTpBrDp(1)  - Time to initiate deployment of tip brake 1 (s)
9999.9      TTpBrDp(2)  - Time to initiate deployment of tip brake 2 (s)
9999.9      TTpBrDp(3)  - Time to initiate deployment of tip brake 3 (s) [unused for 2 blades]
9999.9      TBDepISp(1) - Deployment-initiation speed for the tip brake on blade 1 (rpm)
9999.9      TBDepISp(2) - Deployment-initiation speed for the tip brake on blade 2 (rpm)
9999.9      TBDepISp(3) - Deployment-initiation speed for the tip brake on blade 3 (rpm) [unused for 2 blades]
9999.9      TYawManS    - Time to start override yaw maneuver and end standard yaw control (s)
9999.9      TYawManE    - Time at which override yaw maneuver reaches final yaw angle (s)
60      NacYawF     - Final yaw angle for override yaw maneuvers (degrees)
9999.9      TPitManS(1) - Time to start override pitch maneuver for blade 1 and end standard pitch control (s)
9999.9      TPitManS(2) - Time to start override pitch maneuver for blade 2 and end standard pitch control (s)
9999.9      TPitManS(3) - Time to start override pitch maneuver for blade 3 and end standard pitch control (s) [unused for 2 blades]
9999.9      TPitManE(1) - Time at which override pitch maneuver for blade 1 reaches final pitch (s)
9999.9      TPitManE(2) - Time at which override pitch maneuver for blade 2 reaches final pitch (s)
9999.9      TPitManE(3) - Time at which override pitch maneuver for blade 3 reaches final pitch (s) [unused for 2 blades]
0      BlPitch(1)  - Blade 1 initial pitch (degrees)
0      BlPitch(2)  - Blade 2 initial pitch (degrees)
0      BlPitch(3)  - Blade 3 initial pitch (degrees) [unused for 2 blades]
0      BlPitchF(1) - Blade 1 final pitch for pitch maneuvers (degrees)
0      BlPitchF(2) - Blade 2 final pitch for pitch maneuvers (degrees)
0      BlPitchF(3) - Blade 3 final pitch for pitch maneuvers (degrees) [unused for 2 blades]
---------------------- ENVIRONMENTAL CONDITIONS --------------------------------
   9.80665  Gravity     - Gravitational acceleration (m/s^2)
---------------------- FEATURE FLAGS -------------------------------------------
True        FlapDOF1    - First flapwise blade mode DOF (flag)
True        FlapDOF2    - Second flapwise blade mode DOF (flag)
True        EdgeDOF     - First edgewise blade mode DOF (flag)
False       TeetDOF     - Rotor-teeter DOF (flag) [unused for 3 blades]
True        DrTrDOF     - Drivetrain rotational-flexibility DOF (flag)
True        GenDOF      - Generator DOF (flag)
True        YawDOF      - Yaw DOF (flag)
True        TwFADOF1    - First fore-aft tower bending-mode DOF (flag)
True        TwFADOF2    - Second fore-aft tower bending-mode DOF (flag)
True        TwSSDOF1    - First side-to-side tower bending-mode DOF (flag)
True        TwSSDOF2    - Second side-to-side tower bending-mode DOF (flag)
True        CompAero    - Compute aerodynamic forces (flag)
False       CompNoise   - Compute aerodynamic noise (flag)
---------------------- INITIAL CONDITIONS --------------------------------------
   0.0      OoPDefl     - Initial out-of-plane blade-tip displacement (meters)
   0.0      IPDefl      - Initial in-plane blade-tip deflection (meters)
   0.0      TeetDefl    - Initial or fixed teeter angle (degrees) [unused for 3 blades]
   0.0      Azimuth     - Initial azimuth angle for blade 1 (degrees)
   0.0      RotSpeed    - Initial or fixed rotor speed (rpm)
60      NacYaw      - Initial or fixed nacelle-yaw angle (degrees)
   0.0      TTDspFA     - Initial fore-aft tower-top displacement (meters)
   0.0      TTDspSS     - Initial side-to-side tower-top displacement (meters)
---------------------- TURBINE CONFIGURATION -----------------------------------
  63.0      TipRad      - The distance from the rotor apex to the blade tip (meters)
   1.5      HubRad      - The distance from the rotor apex to the blade root (meters)
   1        PSpnElN     - Number of the innermost blade element which is still part of the pitchable portion of the blade for partial-span pitch control [1 to BldNodes] [CURRENTLY IGNORED] (-)
   0.0      UndSling    - Undersling length [distance from teeter pin to the rotor apex] (meters) [unused for 3 blades]
   0.0      HubCM       - Distance from rotor apex to hub mass [positive downwind] (meters)
  -5.01910  OverHang    - Distance from yaw axis to rotor apex [3 blades] or teeter pin [2 blades] (meters)
   1.9      NacCMxn     - Downwind distance from the tower-top to the nacelle CM (meters)
   0.0      NacCMyn     - Lateral  distance from the tower-top to the nacelle CM (meters)
   1.75     NacCMzn     - Vertical distance from the tower-top to the nacelle CM (meters)
  87.6      TowerHt     - Height of tower above ground level [onshore] or MSL [offshore] (meters)
   1.96256  Twr2Shft    - Vertical distance from the tower-top to the rotor shaft (meters)
   0.0      TwrRBHt     - Tower rigid base height (meters)
  -5.0      ShftTilt    - Rotor shaft tilt angle (degrees)
   0.0      Delta3      - Delta-3 angle for teetering rotors (degrees) [unused for 3 blades]
  -2.5      PreCone(1)  - Blade 1 cone angle (degrees)
  -2.5      PreCone(2)  - Blade 2 cone angle (degrees)
  -2.5      PreCone(3)  - Blade 3 cone angle (degrees) [unused for 2 blades]
   0.0      AzimB1Up    - Azimuth value to use for I/O when blade 1 points up (degrees)
---------------------- MASS AND INERTIA ----------------------------------------
   0.0      YawBrMass   - Yaw bearing mass (kg)
 240.00E3   NacMass     - Nacelle mass (kg)
  56.78E3   HubMass     - Hub mass (kg)
   0.0      TipMass(1)  - Tip-brake mass, blade 1 (kg)
   0.0      TipMass(2)  - Tip-brake mass, blade 2 (kg)
   0.0      TipMass(3)  - Tip-brake mass, blade 3 (kg) [unused for 2 blades]
2607.89E3   NacYIner    - Nacelle inertia about yaw axis (kg m^2)
 534.116    GenIner     - Generator inertia about HSS (kg m^2)
 115.926E3  HubIner     - Hub inertia about rotor axis [3 blades] or teeter axis [2 blades] (kg m^2)
---------------------- DRIVETRAIN ----------------------------------------------
 60.0      GBoxEff     - Gearbox efficiency (%)
  94.4      GenEff      - Generator efficiency [ignored by the Thevenin and user-defined generator models] (%)
  97.0      GBRatio     - Gearbox ratio (-)
False       GBRevers    - Gearbox reversal {T: if rotor and generator rotate in opposite directions} (flag)
  28.1162E3 HSSBrTqF    - Fully deployed HSS-brake torque (N-m)
   0.6      HSSBrDT     - Time for HSS-brake to reach full deployment once initiated (sec) [used only when HSSBrMode=1]
"Dummy"     DynBrkFi    - File containing a mech-gen-torque vs HSS-speed curve for a dynamic brake [CURRENTLY IGNORED] (quoted string)
 867.637E6  DTTorSpr    - Drivetrain torsional spring (N-m/rad)
   6.215E6  DTTorDmp    - Drivetrain torsional damper (N-m/(rad/s))
---------------------- SIMPLE INDUCTION GENERATOR ------------------------------
9999.9      SIG_SlPc    - Rated generator slip percentage (%) [used only when VSContrl=0 and GenModel=1]
9999.9      SIG_SySp    - Synchronous (zero-torque) generator speed (rpm) [used only when VSContrl=0 and GenModel=1]
9999.9      SIG_RtTq    - Rated torque (N-m) [used only when VSContrl=0 and GenModel=1]
9999.9      SIG_PORt    - Pull-out ratio (Tpullout/Trated) (-) [used only when VSContrl=0 and GenModel=1]
---------------------- THEVENIN-EQUIVALENT INDUCTION GENERATOR -----------------
9999.9      TEC_Freq    - Line frequency [50 or 60] (Hz) [used only when VSContrl=0 and GenModel=2]
9998        TEC_NPol    - Number of poles [even integer > 0] (-) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_SRes    - Stator resistance (ohms) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_RRes    - Rotor resistance (ohms) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_VLL     - Line-to-line RMS voltage (volts) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_SLR     - Stator leakage reactance (ohms) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_RLR     - Rotor leakage reactance (ohms) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_MR      - Magnetizing reactance (ohms) [used only when VSContrl=0 and GenModel=2]
---------------------- PLATFORM ------------------------------------------------
   2        PtfmModel   - Platform model {0: none, 1: onshore, 2: fixed bottom offshore, 3: floating offshore} (switch)
"DLC6.2-yaw=60-Angle=0_1-Platform_Fixed.dat"   PtfmFile    - Name of file containing platform properties (quoted string) [unused when PtfmModel=0]
---------------------- TOWER ---------------------------------------------------
  108        TwrNodes    - Number of tower nodes used for analysis (-)
"NRELOffshrBsline5MW_Tower_Monopile_RF_Fixed.dat"      TwrFile     - Name of file containing tower properties (quoted string)
---------------------- NACELLE-YAW ---------------------------------------------
9028.32E6   YawSpr      - Nacelle-yaw spring constant (N-m/rad)
  19.16E6   YawDamp     - Nacelle-yaw damping constant (N-m/(rad/s))
60      YawNeut     - Neutral yaw position--yaw spring force is zero at this yaw (degrees)
---------------------- FURLING -------------------------------------------------
False       Furling     - Read in additional model properties for furling turbine (flag)
"Dummy"     FurlFile    - Name of file containing furling properties (quoted string) [unused when Furling=False]
---------------------- ROTOR-TEETER --------------------------------------------
   0        TeetMod     - Rotor-teeter spring/damper model {0: none, 1: standard, 2: user-defined from routine UserTeet} (switch) [unused for 3 blades]
   0.0      TeetDmpP    - Rotor-teeter damper position (degrees) [used only for 2 blades and when TeetMod=1]
   0.0      TeetDmp     - Rotor-teeter damping constant (N-m/(rad/s)) [used only for 2 blades and when TeetMod=1]
   0.0      TeetCDmp    - Rotor-teeter rate-independent Coulomb-damping moment (N-m) [used only for 2 blades and when TeetMod=1]
   0.0      TeetSStP    - Rotor-teeter soft-stop position (degrees) [used only for 2 blades and when TeetMod=1]
   0.0      TeetHStP    - Rotor-teeter hard-stop position (degrees) [used only for 2 blades and when TeetMod=1]
   0.0      TeetSSSp    - Rotor-teeter soft-stop linear-spring constant (N-m/rad) [used only for 2 blades and when TeetMod=1]
   0.0      TeetHSSp    - Rotor-teeter hard-stop linear-spring constant (N-m/rad) [used only for 2 blades and when TeetMod=1]
---------------------- TIP-BRAKE -----------------------------------------------
   0.0      TBDrConN    - Tip-brake drag constant during normal operation, Cd*Area (m^2)
   0.0      TBDrConD    - Tip-brake drag constant during fully-deployed operation, Cd*Area (m^2)
   0.0      TpBrDT      - Time for tip-brake to reach full deployment once released (sec)
---------------------- BLADE ---------------------------------------------------
"NRELOffshrBsline5MW_Blade.dat"                  BldFile(1)  - Name of file containing properties for blade 1 (quoted string)
"NRELOffshrBsline5MW_Blade.dat"                  BldFile(2)  - Name of file containing properties for blade 2 (quoted string)
"NRELOffshrBsline5MW_Blade.dat"                  BldFile(3)  - Name of file containing properties for blade 3 (quoted string) [unused for 2 blades]
---------------------- AERODYN -------------------------------------------------
"DLC6.2-yaw=60-Angle=0_1-AeroDyn_Fixed.ipt"                ADFile      - Name of file containing AeroDyn input parameters (quoted string)
---------------------- NOISE ---------------------------------------------------
"Dummy"     NoiseFile   - Name of file containing aerodynamic noise input parameters (quoted string) [used only when CompNoise=True]
---------------------- ADAMS ---------------------------------------------------
"NRELOffshrBsline5MW_ADAMSSpecific.dat"          ADAMSFile   - Name of file containing ADAMS-specific input parameters (quoted string) [unused when ADAMSPrep=1]
---------------------- LINEARIZATION CONTROL -----------------------------------
"NRELOffshrBsline5MW_Linear.dat"                 LinFile     - Name of file containing FAST linearization parameters (quoted string) [unused when AnalMode=1]
---------------------- OUTPUT --------------------------------------------------
True        SumPrint    - Print summary data to "<RootName>.fsm" (flag)
1           OutFileFmt  - Format for tabular (time-marching) output files (1: text file[<RootName>.out], 2: Binary file [<RootName>.outb], 3: both) (switch)
True        TabDelim    - Generate a tab-delimited tabular output file. (flag)
"ES10.3E2"  OutFmt      - Format used for tabular output except time.  Resulting field should be 10 characters. (quoted string)  [not checked for validity!]
  30.0      TStart      - Time to begin tabular output (s)
   50        DecFact     - Decimation factor for tabular output {1: output every time step} (-)
   1.0      SttsTime    - Amount of time between screen status messages (sec)
  -3.09528  NcIMUxn     - Downwind distance from the tower-top to the nacelle IMU (meters)
   0.0      NcIMUyn     - Lateral  distance from the tower-top to the nacelle IMU (meters)
   2.23336  NcIMUzn     - Vertical distance from the tower-top to the nacelle IMU (meters)
   1.912    ShftGagL    - Distance from rotor apex [3 blades] or teeter pin [2 blades] to shaft strain gages [positive for upwind rotors] (meters)
   9        NTwGages    - Number of tower nodes that have strain gages for output [0 to 9] (-)
1,21,41,51,61,71,81,91,108    TwrGagNd    - List of tower nodes that have strain gages [1 to TwrNodes] (-) [unused if NTwGages=0]
   0        NBlGages    - Number of blade nodes that have strain gages for output [0 to 9] (-)
 5,9,13     BldGagNd    - List of blade nodes that have strain gages [1 to BldNodes] (-) [unused if NBlGages=0]
            OutList     - The next line(s) contains a list of output parameters.  See OutList.txt for a listing of available output channels, (-)
"WindVxi  , WindVyi  , WindVzi"                              - Longitudinal, lateral, and vertical wind speeds
"WaveElev"                                                   - Wave elevation at the platform reference point
"RotSpeed , GenSpeed"                                        - Low-speed shaft and high-speed shaft speeds
"TTDspFA  , TTDspSS"                            - Tower fore-aft and side-to-side displacements
"PtchPMzc1, PtchPMzc2, PtchPMzc3"                                        - Pitch angle
"TwrBsFxt , TwrBsFyt , TwrBsFzt"                             - Fore-aft shear, side-to-side shear, and vertical forces at the mudline
"TwrBsMxt , TwrBsMyt , TwrBsMzt"                             - Side-to-side bending, fore-aft bending, and yaw moments at the mudline
"PtfmSurge, PtfmSway , PtfmRoll , PtfmPitch"                 - Platform surge, sway, roll, and pitch displacements (for use in calculating in Crunch the tower-top displacements in the inertia frame)
"YawBrFxp , YawBrFyp , YawBrFzp"                             - Fore-aft shear, side-to-side shear, and vertical forces at the top of the tower (not rotating with nacelle yaw)
"YawBrMxp , YawBrMyp , YawBrMzp"                             - Side-to-side bending, fore-aft bending, and yaw moments at the top of the tower (not rotating with nacelle yaw)
"TwHt1FLxt, TwHt1MLyt, TwHt1TDxt"                                       - Local side-to-side and fore-aft bending moments at tower gage
"TwHt2FLxt, TwHt2MLyt, TwHt2TDxt"                                     
"TwHt3FLxt, TwHt3MLyt, TwHt3TDxt"                                       
"TwHt4FLxt, TwHt4MLyt, TwHt4TDxt"                                     
"TwHt5FLxt, TwHt5MLyt, TwHt5TDxt"                                       
"TwHt6FLxt, TwHt6MLyt, TwHt6TDxt"                                     
"TwHt7FLxt, TwHt7MLyt, TwHt7TDxt"                                       
"TwHt8FLxt, TwHt8MLyt, TwHt8TDxt"                                     
"TwHt9FLxt, TwHt9MLyt, TwHt9TDxt"                                       
"RootFxb1, RootFyb1, RootMxb1,RootMyb1"                        -flapwise/edgewise force or moment at blade root
"YawPzn"                        -Nacelle yaw angle (deg)
END of FAST input file (the word "END" must appear in the first 3 columns of this last line).
--------------------------------------------------------------------------------
 
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Jason.Jonkman
Posts: 5738
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Fast errors for extreme load cases

Postby Jason.Jonkman » Fri Apr 09, 2021 8:33 am

Dear Patrick,

Well, it looks like your model has gone numerically unstable, but I'm not sure why.

You haven't shared your AeroDyn input file, but have you disabled the wake calculation and unsteady airfoil aerodynamic calculation as recommend for an idling condition?

Please note that the case you are running sounds very extreme, with four independent failures (loss of control of each of the three blades and loss of yaw control), which is beyond the requirements of IEC design standards.

Please also note that FAST v7 is now quite old; I would generally recommend upgrading to the newest version of FAST (now OpenFAST), unless you have a strong reason to run this older version.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Patrick.Lai
Posts: 7
Joined: Mon Sep 07, 2020 6:52 am
Organization: Hongkong University of science and technology
Location: Hongkong

Re: Fast errors for extreme load cases

Postby Patrick.Lai » Fri Apr 09, 2021 6:38 pm

Dear Jason,

Thanks a lot for your response.

You haven't shared your AeroDyn input file, but have you disabled the wake calculation and unsteady airfoil aerodynamic calculation as recommend for an idling condition?


I have posted the AeroDyn input file as follows, but I am not sure which parameters should be reset to disable the wake calculation and unsteady airfoil aerodynamic calculation. It seems there are no direct options like WakeMod and AFAeroMod in FAST v7.

Code: Select all

NREL 5.0 MW offshore baseline aerodynamic input properties; Compatible with AeroDyn v12.58.
SI          SysUnits    - System of units used for input and output [must be SI for FAST] (unquoted string)
BEDDOES     StallMod    - Dynamic stall included [BEDDOES or STEADY] (unquoted string)
USE_CM      UseCm       - Use aerodynamic pitching moment model? [USE_CM or NO_CM] (unquoted string)
DYNIN       InfModel    - Inflow model [DYNIN or EQUIL] (unquoted string)
WAKE       IndModel    - Induction-factor model [NONE or WAKE or SWIRL] (unquoted string)
   0.005    AToler      - Induction-factor tolerance (convergence criteria) (-)
PRANDtl     TLModel     - Tip-loss model (EQUIL only) [PRANDtl, GTECH, or NONE] (unquoted string)
PRANDtl     HLModel     - Hub-loss model (EQUIL only) [PRANdtl or NONE] (unquoted string)
"DLC6.1-U=42_9.wnd"                             WindFile    - Name of file containing wind data (quoted string)
  90.0      HH          - Wind reference (hub) height [TowerHt+Twr2Shft+OverHang*SIN(ShftTilt)] (m)
   0.0      TwrShad     - Tower-shadow velocity deficit (-)
9999.9      ShadHWid    - Tower-shadow half width (m)
9999.9      T_Shad_Refpt - Tower-shadow reference point (m)
   1.225    AirDens     - Air density (kg/m^3)
   1.464E-5 KinVisc     - Kinematic air viscosity [CURRENTLY IGNORED] (m^2/sec)
   0.02479  DTAero      - Time interval for aerodynamic calculations (sec)
   8        NumFoil     - Number of airfoil files (-)
"AeroData\Cylinder1.dat"                         FoilNm      - Names of the airfoil files [NumFoil lines] (quoted strings)
"AeroData\Cylinder2.dat"
"AeroData\DU40_A17.dat"
"AeroData\DU35_A17.dat"
"AeroData\DU30_A17.dat"
"AeroData\DU25_A17.dat"
"AeroData\DU21_A17.dat"
"AeroData\NACA64_A17.dat"
  17        BldNodes    - Number of blade nodes used for analysis (-)
RNodes   AeroTwst  DRNodes  Chord  NFoil  PrnElm
 2.8667  13.308    2.7333   3.542  1      NOPRINT
 5.6000  13.308    2.7333   3.854  1      NOPRINT
 8.3333  13.308    2.7333   4.167  2      NOPRINT
11.7500  13.308    4.1000   4.557  3      NOPRINT
15.8500  11.480    4.1000   4.652  4      NOPRINT
19.9500  10.162    4.1000   4.458  4      NOPRINT
24.0500   9.011    4.1000   4.249  5      NOPRINT
28.1500   7.795    4.1000   4.007  6      NOPRINT
32.2500   6.544    4.1000   3.748  6      NOPRINT
36.3500   5.361    4.1000   3.502  7      NOPRINT
40.4500   4.188    4.1000   3.256  7      NOPRINT
44.5500   3.125    4.1000   3.010  8      NOPRINT
48.6500   2.319    4.1000   2.764  8      NOPRINT
52.7500   1.526    4.1000   2.518  8      NOPRINT
56.1667   0.863    2.7333   2.313  8      NOPRINT
58.9000   0.370    2.7333   2.086  8      NOPRINT
61.6333   0.106    2.7333   1.419  8      NOPRINT


Please note that the case you are running sounds very extreme, with four independent failures (loss of control of each of the three blades and loss of yaw control), which is beyond the requirements of IEC design standards.


Indeed, the case I am running is very extreme, and as you pointed out, is beyond the requirements of IEC design standards. This extreme case is more related to typhoon conditions. During a typhoon event, the direction of the typhoon can change dramatically during several hours, however, the yaw and pitch system cannot always follow it as the power has been cut off, leading to varied combinations of yaw and pitch angle.

Please also note that FAST v7 is now quite old; I would generally recommend upgrading to the newest version of FAST (now OpenFAST), unless you have a strong reason to run this older version.


Thank you for your kind reminder. The reason I use FAST v7 is that I'd like to model soil-structure interaction. Through comparing, I found the FAST v7 is the most optimal version to achieve this.

Looking very forward to your reply.

Best regards,
Patrick

Jason.Jonkman
Posts: 5738
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Fast errors for extreme load cases

Postby Jason.Jonkman » Fri Apr 09, 2021 9:17 pm

Dear Patrick,

To disable the wake and unsteady airfoil aerodynamic calculations in AeroDyn v12.58, set StallMod = STEADY and IndModel = NONE. Not using these settings may be the cause of the instability you are seeing.

Which soil-structure interaction model are you using in FAST v7? You may be interested to know that a coupled springs (CS) model has been introduced into SubDyn, recently merged into the dev branch of OpenFAST--see: https://github.com/OpenFAST/openfast/pull/537.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Patrick.Lai
Posts: 7
Joined: Mon Sep 07, 2020 6:52 am
Organization: Hongkong University of science and technology
Location: Hongkong

Re: Fast errors for extreme load cases

Postby Patrick.Lai » Sat Apr 10, 2021 5:59 am

Dear Jason,

Thanks a lot for your reply. Following your suggestion, I have set StallMod = STEADY and IndModel = NONE, but I get another error, as shown in the figure.

Glad to hear that CS model is already available in OpenFAST, but in my case, I am going to use a more advanced model, such as p-y model and other multi-spring models, to better reflect the pile-soil interaction. Implementing such a model in FAST v7 is more straightforward to me than in other versions of FAST.

I look forward to your reply.

Best regards,
Patrick
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Jason.Jonkman
Posts: 5738
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Fast errors for extreme load cases

Postby Jason.Jonkman » Mon Apr 12, 2021 8:33 am

Dear Patrick,

You've already disabled the wake calculation, but to eliminate this error, it may help to also set InfModel = EQUIL.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Patrick.Lai
Posts: 7
Joined: Mon Sep 07, 2020 6:52 am
Organization: Hongkong University of science and technology
Location: Hongkong

Re: Fast errors for extreme load cases

Postby Patrick.Lai » Wed Apr 21, 2021 2:51 am

Dear Jason,

Thanks for your comments. It goes well now.

Best regards,
Patrick


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