## Discrepancy RtAeroFxh and YawBrFxp

Discuss theory and modeling of wind-turbine structures.

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Peter.Veldman
Posts: 7
Joined: Tue Jan 26, 2021 5:13 am
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Location: The Netherlands

### Discrepancy RtAeroFxh and YawBrFxp

Dear NREL team,

I am investigating the loads on the yaw bearing of the 15MW NREL reference turbine for a parked condition (not idling). For simplicity I neglected the floater motions and structural deformations of the wind turbine tower and wind turbine blades.

I am running a simulation in a 52.1 m/s constant uniform wind speed with the blades feathered in the wind (90 degrees) without any yaw misalignment. The Aerodyn15.dat settings are in accordance with the settings recommended in a post from J. Jonkman, i.e. WakeMod = 0, AFAeroMod = 1. As well as the Elastodyn.dat settings (GenDOF = False) and Servodyn.dat settings (PCMode = 0). For this specific case I did not take into account the aerodynamic loads on the wind turbine-tower (TwrAero = False).

When looking to the tower-top / yaw bearing fore-aft shear force (YawBrFxp) in this specific simulation, it is noted that this load is equal to approx. 150 kN while the aerodynamic thrust force (RtAeroFxh) is equal to approx. 75 kN. Since the aerodynamic thrust force is the only load component on the yaw bearing, what can be the cause of this (significant) difference?

As far as I understood, openFast does not take the drag loads on the nacelle and hub into account which might be important when considering a yaw misalignment of the nacelle. Is there an appropriate way to take this loading into account? For example increasing the drag coefficient of the highest segment of the tower?

Best regards,

Peter Veldman

P.S.: For completeness I included the input files for Aerodyn, Elastodyn and Servodyn below:

Aerodyn15.dat

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`------- AERODYN v15.03.* INPUT FILE ------------------------------------------------IEA 15 MW Offshore Reference Turbine======  General Options  ============================================================================False                  Echo        - Echo the input to "<rootname>.AD.ech"?  (flag)"default"              DTAero      - Time interval for aerodynamic calculations {or "default"} (s)0                      WakeMod     - Type of wake/induction model (switch) {0=none, 1=BEMT}1                      AFAeroMod   - Type of blade airfoil aerodynamics model (switch) {1=steady model, 2=Beddoes-Leishman unsteady model} [must be 1 when linearizing]1                      TwrPotent   - Type tower influence on wind based on potential flow around the tower (switch) {0=none, 1=baseline potential flow, 2=potential flow with Bak correction}False                  TwrShadow   - Calculate tower influence on wind based on downstream tower shadow? (flag)False               TwrAero     - Calculate tower aerodynamic loads? (flag)False                  FrozenWake  - Assume frozen wake during linearization? (flag) [used only when WakeMod=1 and when linearizing]False                  CavitCheck  - Perform cavitation check? (flag) TRUE will turn off unsteady aerodynamicsFalse                  CompAA      - Flag to compute AeroAcoustics calculation [only used when WakeMod=1 or 2]"AeroAcousticsInput.dat" AA_InputFile - Aeroacoustics input file======  Environmental Conditions  =================================================================== 1.225000000000000e+00 AirDens     - Air density (kg/m^3) 1.479232653061225e-05 KinVisc     - Kinematic air viscosity (m^2/s) 3.350000000000000e+02 SpdSound    - Speed of sound (m/s) 1.035000000000000e+05 Patm        - Atmospheric pressure (Pa) [used only when CavitCheck=True] 1.700000000000000e+03 Pvap        - Vapour pressure of fluid (Pa) [used only when CavitCheck=True] 5.000000000000000e-01 FluidDepth  - Water depth above mid-hub height (m) [used only when CavitCheck=True]======  Blade-Element/Momentum Theory Options  ====================================================== [used only when WakeMod=1]2                      SkewMod     - Type of skewed-wake correction model (switch) {1=uncoupled, 2=Pitt/Peters, 3=coupled} [used only when WakeMod=1]"default"              SkewModFactor - Constant used in Pitt/Peters skewed wake model {or "default" is 15/32*pi} (-) [used only when SkewMod=2; unused when WakeMod=0]True                   TipLoss     - Use the Prandtl tip-loss model? (flag) [used only when WakeMod=1]True                   HubLoss     - Use the Prandtl hub-loss model? (flag) [used only when WakeMod=1]True                   TanInd      - Include tangential induction in BEMT calculations? (flag) [used only when WakeMod=1]True                   AIDrag      - Include the drag term in the axial-induction calculation? (flag) [used only when WakeMod=1]True                   TIDrag      - Include the drag term in the tangential-induction calculation? (flag) [used only when WakeMod=1 and TanInd=TRUE]"Default"              IndToler    - Convergence tolerance for BEMT nonlinear solve residual equation {or "default"} (-) [used only when WakeMod=1]500                    MaxIter     - Maximum number of iteration steps (-) [used only when WakeMod=1]======  Dynamic Blade-Element/Momentum Theory Options  ====================================================== [used only when WakeMod=1]2                      DBEMT_Mod   - Type of dynamic BEMT (DBEMT) model {1=constant tau1, 2=time-dependent tau1} (-) [used only when WakeMod=2]2                      tau1_const  - Time constant for DBEMT (s) [used only when WakeMod=2 and DBEMT_Mod=1]======  OLAF -- cOnvecting LAgrangian Filaments (Free Vortex Wake) Theory Options  ================== [used only when WakeMod=3]"unused"               OLAFInputFileName - Input file for OLAF [used only when WakeMod=3]======  Beddoes-Leishman Unsteady Airfoil Aerodynamics Options  ===================================== [used only when AFAeroMod=2]3                      UAMod       Unsteady Aero Model Switch (switch) {1=Baseline model (Original), 2=Gonzalez's variant (changes in Cn,Cc,Cm), 3=Minemma/Pierce variant (changes in Cc and Cm)} [used only when AFAeroMod=2]True                   FLookup     Flag to indicate whether a lookup for f' will be calculated (TRUE) or whether best-fit exponential equations will be used (FALSE); if FALSE S1-S4 must be provided in airfoil input files (flag) [used only when AFAeroMod=2]======  Airfoil Information =========================================================================1                      AFTabMod    - Interpolation method for multiple airfoil tables {1=1D interpolation on AoA (first table only); 2=2D interpolation on AoA and Re; 3=2D interpolation on AoA and UserProp} (-)1                      InCol_Alfa  - The column in the airfoil tables that contains the angle of attack (-)2                      InCol_Cl    - The column in the airfoil tables that contains the lift coefficient (-)3                      InCol_Cd    - The column in the airfoil tables that contains the drag coefficient (-)4                      InCol_Cm    - The column in the airfoil tables that contains the pitching-moment coefficient; use zero if there is no Cm column (-)0                      InCol_Cpmin - The column in the airfoil tables that contains the Cpmin coefficient; use zero if there is no Cpmin column (-)50                     NumAFfiles  - Number of airfoil files used (-)"Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_00.dat"    AFNames            - Airfoil file names (NumAFfiles lines) (quoted strings)"Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_01.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_02.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_03.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_04.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_05.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_06.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_07.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_08.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_09.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_10.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_11.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_12.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_13.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_14.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_15.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_16.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_17.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_18.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_19.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_20.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_21.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_22.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_23.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_24.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_25.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_26.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_27.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_28.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_29.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_30.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_31.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_32.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_33.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_34.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_35.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_36.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_37.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_38.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_39.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_40.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_41.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_42.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_43.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_44.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_45.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_46.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_47.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_48.dat""Airfoils/IEA-15-240-RWT_AeroDyn15_Polar_49.dat"======  Rotor/Blade Properties  =====================================================================True                      UseBlCm     - Include aerodynamic pitching moment in calculations?  (flag)"AeroDyn15_blade.dat"    ADBlFile(1) - Name of file containing distributed aerodynamic properties for Blade #1 (-)"AeroDyn15_blade.dat"    ADBlFile(2) - Name of file containing distributed aerodynamic properties for Blade #2 (-) [unused if NumBl < 2]"AeroDyn15_blade.dat"    ADBlFile(3) - Name of file containing distributed aerodynamic properties for Blade #3 (-) [unused if NumBl < 3]======  Tower Influence and Aerodynamics ============================================================= [used only when TwrPotent/=0, TwrShadow=True, or TwrAero=True]11                     NumTwrNds   - Number of tower nodes used in the analysis  (-) [used only when TwrPotent/=0, TwrShadow=True, or TwrAero=True]TwrElev        TwrDiam        TwrCd(m)              (m)           (-)  15.           10.             1.  28.           10.             1.  41.            9.926          1.  54.            9.443          1.  67.            8.833          1.  80.            8.151          1.  93.            7.39           1. 106.            6.909          1. 119.            6.748          1. 132.            6.572          1. 144.495         6.5            1.======  Tower Influence and Aerodynamics ============================================================= [used only when TwrPotent/=0, TwrShadow=True, or TwrAero=True]True                   SumPrint    - Generate a summary file listing input options and interpolated properties to "<rootname>.AD.sum"?  (flag)9                      NBlOuts     - Number of blade node outputs [0 - 9] (-)1, 6, 11, 20, 30, 38, 43, 47, 50 BlOutNd     - Blade nodes whose values will be output  (-)0                      NTwOuts     - Number of tower node outputs [0 - 9]  (-)1, 2, 3, 4, 5          TwOutNd     - Tower nodes whose values will be output  (-)                   OutList             - The next line(s) contains a list of output parameters.  See OutListParameters.xlsx for a listing of available output channels, (-)"RtAeroFxh""RtAeroFyh""RtAeroFzh""RtAeroMxh""RtAeroMyh""RtAeroMzh""RtVAvgxh""RtAeroCp""RtTSR"END of input file (the word "END" must appear in the first 3 columns of this last OutList line)---------------------------------------------------------------------------------------`

Elastodyn.dat

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`------- ELASTODYN v1.03.* INPUT FILE -------------------------------------------IEA 15 MW offshore reference model on UMaine VolturnUS-S semi-submersible floating platform---------------------- SIMULATION CONTROL --------------------------------------False         Echo        - Echo input data to "<RootName>.ech" (flag)          3   Method      - Integration method: {1: RK4, 2: AB4, or 3: ABM4} (-)"default"     DT          Integration time step (s)---------------------- ENVIRONMENTAL CONDITION ---------------------------------    9.80665   Gravity     - Gravitational acceleration (m/s^2)---------------------- DEGREES OF FREEDOM --------------------------------------False          FlapDOF1    - First flapwise blade mode DOF (flag)False          FlapDOF2    - Second flapwise blade mode DOF (flag)False          EdgeDOF     - First edgewise blade mode DOF (flag)False         TeetDOF     - Rotor-teeter DOF (flag) [unused for 3 blades]False         DrTrDOF     - Drivetrain rotational-flexibility DOF (flag)False          GenDOF      - Generator DOF (flag)False         YawDOF      - Yaw DOF (flag)False          TwFADOF1    - First fore-aft tower bending-mode DOF (flag)False          TwFADOF2    - Second fore-aft tower bending-mode DOF (flag)False          TwSSDOF1    - First side-to-side tower bending-mode DOF (flag)False          TwSSDOF2    - Second side-to-side tower bending-mode DOF (flag)False          PtfmSgDOF   - Platform horizontal surge translation DOF (flag)False          PtfmSwDOF   - Platform horizontal sway translation DOF (flag)False          PtfmHvDOF   - Platform vertical heave translation DOF (flag)False          PtfmRDOF    - Platform roll tilt rotation DOF (flag)False          PtfmPDOF    - Platform pitch tilt rotation DOF (flag)False          PtfmYDOF    - Platform yaw rotation DOF (flag)---------------------- INITIAL CONDITIONS --------------------------------------          0   OoPDefl     - Initial out-of-plane blade-tip displacement (meters)          0   IPDefl      - Initial in-plane blade-tip deflection (meters)         90   BlPitch(1)  - Blade 1 initial pitch (degrees)         90   BlPitch(2)  - Blade 2 initial pitch (degrees)         90   BlPitch(3)  - Blade 3 initial pitch (degrees) [unused for 2 blades]          0   TeetDefl    - Initial or fixed teeter angle (degrees) [unused for 3 blades]          0   Azimuth     - Initial azimuth angle for blade 1 (degrees)          0   RotSpeed    - Initial or fixed rotor speed (rpm)          0   NacYaw      - Initial or fixed nacelle-yaw angle (degrees)          0   TTDspFA     - Initial fore-aft tower-top displacement (meters)          0   TTDspSS     - Initial side-to-side tower-top displacement (meters)          0   PtfmSurge   - Initial or fixed horizontal surge translational displacement of platform (meters)          0   PtfmSway    - Initial or fixed horizontal sway translational displacement of platform (meters)          0   PtfmHeave   - Initial or fixed vertical heave translational displacement of platform (meters)          0   PtfmRoll    - Initial or fixed roll tilt rotational displacement of platform (degrees)          0   PtfmPitch   - Initial or fixed pitch tilt rotational displacement of platform (degrees)          0   PtfmYaw     - Initial or fixed yaw rotational displacement of platform (degrees)---------------------- TURBINE CONFIGURATION -----------------------------------          3   NumBl       - Number of blades (-)        120   TipRad      - The distance from the rotor apex to the blade tip (meters)          3   HubRad      - The distance from the rotor apex to the blade root (meters)         -4   PreCone(1)  - Blade 1 cone angle (degrees)         -4   PreCone(2)  - Blade 2 cone angle (degrees)         -4   PreCone(3)  - Blade 3 cone angle (degrees) [unused for 2 blades]          0   HubCM       - Distance from rotor apex to hub mass [positive downwind] (meters)          0   UndSling    - Undersling length [distance from teeter pin to the rotor apex] (meters) [unused for 3 blades]          0   Delta3      - Delta-3 angle for teetering rotors (degrees) [unused for 3 blades]          0   AzimB1Up    - Azimuth value to use for I/O when blade 1 points up (degrees)    -11.075   OverHang    - Distance from yaw axis to rotor apex [3 blades] or teeter pin [2 blades] (meters)          0   ShftGagL    - Distance from rotor apex [3 blades] or teeter pin [2 blades] to shaft strain gages [positive for upwind rotors] (meters)         -6   ShftTilt    - Rotor shaft tilt angle (degrees)     -4.985   NacCMxn     - Downwind distance from the tower-top to the nacelle CM (meters)          0   NacCMyn     - Lateral  distance from the tower-top to the nacelle CM (meters)      4.358   NacCMzn     - Vertical distance from the tower-top to the nacelle CM (meters)     -4.985   NcIMUxn     - Downwind distance from the tower-top to the nacelle IMU (meters)          0   NcIMUyn     - Lateral  distance from the tower-top to the nacelle IMU (meters)      4.358   NcIMUzn     - Vertical distance from the tower-top to the nacelle IMU (meters)     4.3478   Twr2Shft    - Vertical distance from the tower-top to the rotor shaft (meters)    144.495   TowerHt     - Height of tower above ground level [onshore] or MSL [offshore] (meters)          15   TowerBsHt   - Height of tower base above ground level [onshore] or MSL [offshore] (meters)          0   PtfmCMxt    - Downwind distance from the ground level [onshore] or MSL [offshore] to the platform CM (meters)          0   PtfmCMyt    - Lateral distance from the ground level [onshore] or MSL [offshore] to the platform CM (meters)     -14.94   PtfmCMzt    - Vertical distance from the ground level [onshore] or MSL [offshore] to the platform CM (meters)          0   PtfmRefzt   - Vertical distance from the ground level [onshore] or MSL [offshore] to the platform reference point (meters)---------------------- MASS AND INERTIA ----------------------------------------          0   TipMass(1)  - Tip-brake mass, blade 1 (kg)          0   TipMass(2)  - Tip-brake mass, blade 2 (kg)          0   TipMass(3)  - Tip-brake mass, blade 3 (kg) [unused for 2 blades]     190000   HubMass     - Hub mass (kg)1.37347E+06   HubIner     - Hub inertia about rotor axis [3 blades] or teeter axis [2 blades] (kg m^2)8.00865E+06   GenIner     - Generator inertia about HSS (kg m^2)     507275   NacMass     - Nacelle mass (kg)1.96179E+07   NacYIner    - Nacelle inertia about yaw axis (kg m^2)     100000   YawBrMass   - Yaw bearing mass (kg)1.7838E+07    PtfmMass    - Platform mass (kg)1.2507E+10     PtfmRIner   - Platform inertia for roll tilt rotation about the platform CM (kg m^2)1.2507E+10     PtfmPIner   - Platform inertia for pitch tilt rotation about the platform CM (kg m^2)2.3667E+10     PtfmYIner   - Platform inertia for yaw rotation about the platform CM (kg m^2)---------------------- BLADE ---------------------------------------------------         20   BldNodes    - Number of blade nodes (per blade) used for analysis (-)"ElastoDyn_blade.dat"    BldFile1    - Name of file containing properties for blade 1 (quoted string)"ElastoDyn_blade.dat"    BldFile2    - Name of file containing properties for blade 2 (quoted string)"ElastoDyn_blade.dat"    BldFile3    - Name of file containing properties for blade 3 (quoted string) [unused for 2 blades]---------------------- 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   TeetDmpP    - Rotor-teeter damper position (degrees) [used only for 2 blades and when TeetMod=1]          0   TeetDmp     - Rotor-teeter damping constant (N-m/(rad/s)) [used only for 2 blades and when TeetMod=1]          0   TeetCDmp    - Rotor-teeter rate-independent Coulomb-damping moment (N-m) [used only for 2 blades and when TeetMod=1]          0   TeetSStP    - Rotor-teeter soft-stop position (degrees) [used only for 2 blades and when TeetMod=1]          0   TeetHStP    - Rotor-teeter hard-stop position (degrees) [used only for 2 blades and when TeetMod=1]          0   TeetSSSp    - Rotor-teeter soft-stop linear-spring constant (N-m/rad) [used only for 2 blades and when TeetMod=1]          0   TeetHSSp    - Rotor-teeter hard-stop linear-spring constant (N-m/rad) [used only for 2 blades and when TeetMod=1]---------------------- DRIVETRAIN ----------------------------------------------        100   GBoxEff     - Gearbox efficiency (%)          1   GBRatio     - Gearbox ratio (-)  8.235E+11   DTTorSpr    - Drivetrain torsional spring (N-m/rad)  6.215E+06   DTTorDmp    - Drivetrain torsional damper (N-m/(rad/s))---------------------- FURLING -------------------------------------------------False         Furling     - Read in additional model properties for furling turbine (flag) [must currently be FALSE)"unused"      FurlFile    - Name of file containing furling properties (quoted string) [unused when Furling=False]---------------------- TOWER ---------------------------------------------------         50   TwrNodes    - Number of tower nodes used for analysis (-)"ElastoDyn_tower.dat"    TwrFile     - Name of file containing tower properties (quoted string)---------------------- OUTPUT --------------------------------------------------True         SumPrint    - Print summary data to "<RootName>.sum" (flag)          1   OutFile     - Switch to determine where output will be placed: {1: in module output file only; 2: in glue code output file only; 3: both} (currently unused)True          TabDelim    - Use tab delimiters in text tabular output file? (flag) (currently unused)"ES10.3E2"    OutFmt      - Format used for text tabular output (except time).  Resulting field should be 10 characters. (quoted string) (currently unused)          0   TStart      - Time to begin tabular output (s) (currently unused)          1   DecFact     - Decimation factor for tabular output {1: output every time step} (-) (currently unused)          1   NTwGages    - Number of tower nodes that have strain gages for output [0 to 9] (-)         20   TwrGagNd    - List of tower nodes that have strain gages [1 to TwrNodes] (-) [unused if NTwGages=0] TwrGagNd    - List of tower nodes that have strain gages [1 to TwrNodes] (-) [unused if NTwGages=0] TwrGagNd    - List of tower nodes that have strain gages [1 to TwrNodes] (-) [unused if NTwGages=0]          3   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] BldGagNd    - List of blade nodes that have strain gages [1 to BldNodes] (-) [unused if NBlGages=0] 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 OutListParameters.xlsx for a listing of available output channels, (-)                 "Azimuth"                  "BldPitch1"                "GenSpeed"                 "IPDefl1"                  "LSSGagMya"                "LSSGagMza"                "OoPDefl1"                 "PtfmSurge"                "PtfmSway"                 "PtfmHeave"                "PtfmRoll"                 "PtfmPitch"                "PtfmYaw"                  "RootFxb1"                 "RootFyb1"                 "RootFzb1"                 "RootMxb1"                 "RootMyb1"                 "RootMzb1"                 "RootFxb2"                 "RootFyb2"                 "RootFzb2"                 "RootMxb2"                 "RootMyb2"                 "RootMzb2"                 "RootFxb3"                 "RootFyb3"                 "RootFzb3"                 "RootMxb3"                 "RootMyb3"                 "RootMzb3"                 "TipDxb1"                  "TipDyb1"                  "TipDxb2"                  "TipDyb2"                  "TipDxb3"                  "TipDyb3"                  "NcIMUTAxs"                "NcIMUTAys"                "NcIMUTAzs"                "YawBrTDxt"                "YawBrTDyt"                "RotSpeed"                 "RotTorq"                  "RotThrust""RotPwr"                                  "Spn2MLxb1"                "Spn2MLyb1"                "TwrBsFxt"                 "TwrBsFyt"                 "TwrBsFzt"                 "TwrBsMxt"                 "TwrBsMyt"                 "TwrBsMzt"                 "TTDspTwst"                "TwHt1TPxi"                "TwHt1TPyi"                "TwstDefl1"                "YawBrFxp"                 "YawBrFyp"                 "YawBrFzp"                 "YawBrMxp"                 "YawBrMyp"                 "YawBrMzp"                 "TwrBsFzt"                 "NacYaw"END of input file (the word "END" must appear in the first 3 columns of this last OutList line)---------------------------------------------------------------------------------------`

Servodyn.dat

Code: Select all

`------- SERVODYN v1.05.* INPUT FILE --------------------------------------------IEA 15 MW offshore reference model on UMaine VolturnUS-S semi-submersible floating platform---------------------- SIMULATION CONTROL --------------------------------------False                  Echo        - Echo input data to <RootName>.ech (flag)"default"              DT          - Communication interval for controllers (s) (or "default")---------------------- PITCH CONTROL -------------------------------------------0                      PCMode      - Pitch control mode {0: none, 3: user-defined from routine PitchCntrl, 4: user-defined from Simulink/Labview, 5: user-defined from Bladed-style DLL} (switch)0.0                    TPCOn       - Time to enable active pitch control (s) [unused when PCMode=0]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]2.0                    PitManRat(1) - Pitch rate at which override pitch maneuver heads toward final pitch angle for blade 1 (deg/s)2.0                    PitManRat(2) - Pitch rate at which override pitch maneuver heads toward final pitch angle for blade 2 (deg/s)2.0                    PitManRat(3) - Pitch rate at which override pitch maneuver heads toward final pitch angle for blade 3 (deg/s) [unused for 2 blades]0.0                    BlPitchF(1) - Blade 1 final pitch for pitch maneuvers (degrees)0.0                    BlPitchF(2) - Blade 2 final pitch for pitch maneuvers (degrees)0.0                    BlPitchF(3) - Blade 3 final pitch for pitch maneuvers (degrees) [unused for 2 blades]---------------------- GENERATOR AND TORQUE CONTROL ----------------------------0                      VSContrl    - Variable-speed control mode {0: none, 1: simple VS, 3: user-defined from routine UserVSCont, 4: user-defined from Simulink/Labview, 5: user-defined from Bladed-style DLL} (switch)2                      GenModel    - Generator model {1: simple, 2: Thevenin, 3: user-defined from routine UserGen} (switch) [used only when VSContrl=0]96.55                   GenEff      - Generator efficiency [ignored by the Thevenin and user-defined generator models] (%)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]---------------------- SIMPLE VARIABLE-SPEED TORQUE CONTROL --------------------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]---------------------- 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]---------------------- HIGH-SPEED SHAFT BRAKE ----------------------------------0                      HSSBrMode   - HSS brake model {0: none, 1: simple, 3: user-defined from routine UserHSSBr, 4: user-defined from Simulink/Labview, 5: user-defined from Bladed-style DLL} (switch)9999.9                 THSSBrDp    - Time to initiate deployment of the HSS brake (s)0.6                    HSSBrDT     - Time for HSS-brake to reach full deployment once initiated (sec) [used only when HSSBrMode=1]28116.2                HSSBrTqF    - Fully deployed HSS-brake torque (N-m)---------------------- NACELLE-YAW CONTROL -------------------------------------0                      YCMode      - Yaw control mode {0: none, 3: user-defined from routine UserYawCont, 4: user-defined from Simulink/Labview, 5: user-defined from Bladed-style DLL} (switch)9999.9                 TYCOn       - Time to enable active yaw control (s) [unused when YCMode=0]0.0                    YawNeut     - Neutral yaw position--yaw spring force is zero at this yaw (degrees)4.6273E+10             YawSpr      - Nacelle-yaw spring constant (N-m/rad)3.9088E+07             YawDamp     - Nacelle-yaw damping constant (N-m/(rad/s))9999.9                 TYawManS    - Time to start override yaw maneuver and end standard yaw control (s)2.0                    YawManRat   - Yaw maneuver rate (in absolute value) (deg/s)0.0                    NacYawF     - Final yaw angle for override yaw maneuvers (degrees)---------------------- TUNED MASS DAMPER ---------------------------------------False                  CompNTMD    - Compute nacelle tuned mass damper {true/false} (flag)"unused"               NTMDfile    - Name of the file for nacelle tuned mass damper (quoted string) [unused when CompNTMD is false]False                  CompTTMD    - Compute tower tuned mass damper {true/false} (flag)"unused"               TTMDfile    - Name of the file for tower tuned mass damper (quoted string) [unused when CompTTMD is false]---------------------- BLADED INTERFACE ---------------------------------------- [used only with Bladed Interface]"DISCON.dll" DLL_FileName - Name/location of the dynamic library {.dll [Windows] or .so [Linux]} in the Bladed-DLL format (-) [used only with Bladed Interface]"DISCON-UMaineSemi.IN"   DLL_InFile  - Name of input file sent to the DLL (-) [used only with Bladed Interface]"DISCON"               DLL_ProcName - Name of procedure in DLL to be called (-) [case sensitive; used only with DLL Interface]"default"              DLL_DT      - Communication interval for dynamic library (s) (or "default") [used only with Bladed Interface]False                  DLL_Ramp    - Whether a linear ramp should be used between DLL_DT time steps [introduces time shift when true] (flag) [used only with Bladed Interface]9999.9                 BPCutoff    - Cuttoff frequency for low-pass filter on blade pitch from DLL (Hz) [used only with Bladed Interface]0.0                    NacYaw_North - Reference yaw angle of the nacelle when the upwind end points due North (deg) [used only with Bladed Interface]0                      Ptch_Cntrl  - Record 28: Use individual pitch control {0: collective pitch; 1: individual pitch control} (switch) [used only with Bladed Interface]0.0                    Ptch_SetPnt - Record  5: Below-rated pitch angle set-point (deg) [used only with Bladed Interface]0.0                    Ptch_Min    - Record  6: Minimum pitch angle (deg) [used only with Bladed Interface]0.0                    Ptch_Max    - Record  7: Maximum pitch angle (deg) [used only with Bladed Interface]0.0                    PtchRate_Min - Record  8: Minimum pitch rate (most negative value allowed) (deg/s) [used only with Bladed Interface]0.0                    PtchRate_Max - Record  9: Maximum pitch rate  (deg/s) [used only with Bladed Interface]0.0                    Gain_OM     - Record 16: Optimal mode gain (Nm/(rad/s)^2) [used only with Bladed Interface]0.0                    GenSpd_MinOM - Record 17: Minimum generator speed (rpm) [used only with Bladed Interface]0.0                    GenSpd_MaxOM - Record 18: Optimal mode maximum speed (rpm) [used only with Bladed Interface]0.0                    GenSpd_Dem  - Record 19: Demanded generator speed above rated (rpm) [used only with Bladed Interface]0.0                    GenTrq_Dem  - Record 22: Demanded generator torque above rated (Nm) [used only with Bladed Interface]0.0                    GenPwr_Dem  - Record 13: Demanded power (W) [used only with Bladed Interface]---------------------- BLADED INTERFACE TORQUE-SPEED LOOK-UP TABLE -------------0                      DLL_NumTrq  - Record 26: No. of points in torque-speed look-up table {0 = none and use the optimal mode parameters; nonzero = ignore the optimal mode PARAMETERs by setting Record 16 to 0.0} (-) [used only with Bladed Interface]GenSpd_TLU               GenTrq_TLU            (rpm)                    (Nm)                  ---------------------- OUTPUT --------------------------------------------------True                   SumPrint    - Print summary data to <RootName>.sum (flag) (currently unused)1                      OutFile     - Switch to determine where output will be placed: {1: in module output file only; 2: in glue code output file only; 3: both} (currently unused)True                   TabDelim    - Use tab delimiters in text tabular output file? (flag) (currently unused)"ES10.3E2"             OutFmt      - Format used for text tabular output (except time).  Resulting field should be 10 characters. (quoted string) (currently unused)30.0                   TStart      - Time to begin tabular output (s) (currently unused)OutList      - The next line(s) contains a list of output parameters.  "GenPwr""GenTq"END of input file (the word "END" must appear in the first 3 columns of this last Out_List line)---------------------------------------------------------------------------------------`

Jason.Jonkman
Posts: 5763
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

### Re: Discrepancy RtAeroFxh and YawBrFxp

Dear Peter,

I see that the rotor has a -6deg tilt, which means that the RtAeroFxh and YawBrFxp vectors are not aligned. Could there be a transverse force at the rotor (RtAeroFyh or RtAeroFzh) contributing to YawBrFxp? Do you get the answer you expect if you eliminate the shaft tilt (ShftTilt = 0)?

We are working to add drag loads on the nacelle and hub in AeroDyn, but this functionality is not available yet.

I haven't tried increasing the drag coefficient of the tower near the tower top, but that could be an option in the interim.

In our recent update to the former TMD submodel of ServoDyn, now called the structural control (StC) submodel, we've also recently introduced the ability to include user-specified point loads in place of the TMD. This will enable you to apply any point forces you want at any point you want in the blades, nacelle, tower, or substructure of OpenFAST. This functionality was developed in PR # https://github.com/OpenFAST/openfast/pull/607, which as recently merged into the dev branch of OpenFAST. I could see this feature being useful for applying currently unmodeled drag loads.

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

Peter.Veldman
Posts: 7
Joined: Tue Jan 26, 2021 5:13 am
Organization: GustoMSC
Location: The Netherlands

### Re: Discrepancy RtAeroFxh and YawBrFxp

Dear Jason,

Indeed, when I eliminate the shaft tilt (ShftTilt = 0) I get the expected result that RtAeroFxp equates to YawBrFxp. I guess I was concentrating too much on the RtAeroFxp while the RtAeroFyp and specifically the RtAeroFzp is contributing to the YawBrFxp as well due to the shaft tilt.

The structural control submodel sounds like a really interesting feature, which might be useful for applying the drag loads. Nevertheless, looking forward to the functionality of the drag loads on the hub and nacelle.