The tower top fore-aft displacement （YawBrTDxt）is negative

[honorhan]

Dear Sir or Madam,

I have encountered a concern when using OpenFAST to simulate the IEA 15 MW wind turbine. Under a mean wind speed of 10.59 m/s and a turbulence intensity of 20%, the simulation result for YawBrTDxt turns out to be negative. Is this normal? What could be the reason?

The results and settings are as follows:

------- 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, 2=DBEMT, 3=OLAF} [WakeMod cannot be 2 or 3 when linearizing]
1                       AFAeroMod   - Type of blade airfoil aerodynamics model (switch) {1=steady model, 2=Beddoes-Leishman unsteady model} [AFAeroMod 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}
1                      TwrShadow   - Calculate tower influence on wind based on downstream tower shadow (switch) {0=none, 1=Powles model, 2=Eames model}
True                   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) [AFAeroMod must be 1 when CavitCheck=true]
False                  Buoyancy    - Include buoyancy effects? (flag)
False                  CompAA      - Flag to compute AeroAcoustics calculation [only used when WakeMod=1 or 2]
AeroAcousticsInput.dat AA_InputFile - AeroAcoustics input file [used only when CompAA=true]
======  Environmental Conditions  ===================================================================
"default"              AirDens     - Air density (kg/m^3)
"default"              KinVisc     - Kinematic air viscosity (m^2/s)
"default"              SpdSound    - Speed of sound (m/s)
"default"              Patm        - Atmospheric pressure (Pa) [used only when CavitCheck=True]
"default"              Pvap        - Vapour pressure of fluid (Pa) [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} [unused when WakeMod=0 or 3]
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 or 3]
True                   TipLoss     - Use the Prandtl tip-loss model? (flag) [unused when WakeMod=0 or 3]
True                   HubLoss     - Use the Prandtl hub-loss model? (flag) [unused when WakeMod=0 or 3]
True                   TanInd      - Include tangential induction in BEMT calculations? (flag) [unused when WakeMod=0 or 3]
True                   AIDrag      - Include the drag term in the axial-induction calculation? (flag) [unused when WakeMod=0 or 3]
True                   TIDrag      - Include the drag term in the tangential-induction calculation? (flag) [unused when WakeMod=0,3 or TanInd=FALSE]
default                IndToler    - Convergence tolerance for BEMT nonlinear solve residual equation {or "default"} (-) [unused when WakeMod=0 or 3]
500                    MaxIter     - Maximum number of iteration steps (-) [unused when WakeMod=0]
======  Dynamic Blade-Element/Momentum Theory Options  ====================================================== [used only when WakeMod=2]
2                      DBEMT_Mod   - Type of dynamic BEMT (DBEMT) model {1=constant tau1, 2=time-dependent tau1} (-) [used only when WakeMod=2]
29.03                  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]
../IEA-15-240-RWT-OLAF/IEA-15-240-RWT_OLAF.dat 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=Minnema/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]
0.1                    UAStartRad  - Starting radius for dynamic stall (fraction of rotor radius) [used only when AFAeroMod=2]
1.0                    UAEndRad    - Ending radius for dynamic stall (fraction of rotor radius) [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)
"IEA-15-240-RWT_AeroDyn15_blade.dat" ADBlFile(1) - Name of file containing distributed aerodynamic properties for Blade #1 (-)
"IEA-15-240-RWT_AeroDyn15_blade.dat" ADBlFile(2) - Name of file containing distributed aerodynamic properties for Blade #2 (-) [unused if NumBl < 2]
"IEA-15-240-RWT_AeroDyn15_blade.dat" ADBlFile(3) - Name of file containing distributed aerodynamic properties for Blade #3 (-) [unused if NumBl < 3]
======  Hub Properties ============================================================================== [used only when Buoyancy=True]
0.0   VolHub             - Hub volume (m^3)
0.0   HubCenBx           - Hub center of buoyancy x direction offset (m)
======  Nacelle Properties ========================================================================== [used only when Buoyancy=True]
0.0   VolNac             - Nacelle volume (m^3)
0,0,0 NacCenB            - Position of nacelle center of buoyancy from yaw bearing in nacelle coordinates (m)
======  Tail fin Aerodynamics ======================================================================== 
False         TFinAero           - Calculate tail fin aerodynamics model (flag)
"unused"      TFinFile           - Input file for tail fin aerodynamics [used only when TFinAero=True]
======  Tower Influence and Aerodynamics ============================================================= [used only when TwrPotent/=0, TwrShadow/=0, or TwrAero=True]
20                     NumTwrNds   - Number of tower nodes used in the analysis  (-) [used only when TwrPotent/=0, TwrShadow/=0, or TwrAero=True]
TwrElev        TwrDiam        TwrCd         TwrTI      TwrCb !TwrTI used only with TwrShadow=2, TwrCb used only with Buoyancy=True
(m)              (m)           (-)           (-)        (-)
  20.000        10.000         0.5           0.1        0.0
  28.000        10.000         0.5           0.1        0.0
  28.001        10.000         0.5           0.1        0.0
  41.000         9.926         0.5           0.1        0.0
  41.001         9.926         0.5           0.1        0.0
  54.000         9.443         0.5           0.1        0.0
  54.001         9.443         0.5           0.1        0.0
  67.000         8.833         0.5           0.1        0.0
  67.001         8.833         0.5           0.1        0.0
  80.000         8.151         0.5           0.1        0.0
  80.001         8.151         0.5           0.1        0.0
  93.000         7.390         0.5           0.1        0.0
  93.001         7.390         0.5           0.1        0.0
 106.000         6.909         0.5           0.1        0.0
 106.001         6.909         0.5           0.1        0.0
 119.000         6.748         0.5           0.1        0.0
 119.001         6.748         0.5           0.1        0.0
 132.000         6.572         0.5           0.1        0.0
 132.001         6.572         0.5           0.1        0.0
 144.386         6.500         0.5           0.1        0.0
======  Outputs  ====================================================================================
False                  SumPrint    - Generate a summary file listing input options and interpolated properties to "<rootname>.AD.sum"?  (flag)
0                      NBlOuts     - Number of blade node outputs [0 - 9] (-)
6, 11, 16, 21, 25, 30, 35, 40, 45 BlOutNd     - Blade nodes whose values will be output  (-)
0                      NTwOuts     - Number of tower node outputs [0 - 9]  (-)
0                      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, (-)
"RtVAvgxh"
"RtArea"
"RtSpeed"
"RtTSR"
END of input file (the word "END" must appear in the first 3 columns of this last OutList line)
====== Outputs for all blade stations (same ending as above for B1N1.... =========================== [optional section]
   0              BldNd_BladesOut     - Number of blades to output all node information at.  Up to number of blades on turbine. (-)
   "All"          BldNd_BlOutNd       - Future feature will allow selecting a portion of the nodes to output.  Not implemented yet. (-)
                  OutList             - The next line(s) contains a list of output parameters.  See OutListParameters.xlsx for a listing of available output channels, (-)
END (the word "END" must appear in the first 3 columns of this last OutList line in the optional nodal output section)

[jjonkman]

Dear @honorhan,

Can you clarify other settings of your model, such as rotor speed and blade pitch?

You are simulating a condition near rated wind speed, but I see that you've disabled aerodynamic induction, with WakeMod = 0 in AeroDyn, which would normally only be set for parked/idling situations. Are you simulating a parked turbine with the blades feathered? If so, the solution likely makes sense because the aerodynamic thrust on the rotor will be low in that case, and the tower deflection would be dominated by the overhanging weight of the RNA--into the wind.

Best regards,

[honorhan]

dear jjonkman,
Sorry, I uploaded the wrong file. The correct one is as follows:

------- 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)
1                      WakeMod     - Type of wake/induction model (switch) {0=none, 1=BEMT, 2=DBEMT, 3=OLAF} [WakeMod cannot be 2 or 3 when linearizing]
2                      AFAeroMod   - Type of blade airfoil aerodynamics model (switch) {1=steady model, 2=Beddoes-Leishman unsteady model} [AFAeroMod 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}
1                      TwrShadow   - Calculate tower influence on wind based on downstream tower shadow (switch) {0=none, 1=Powles model, 2=Eames model}
True                   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) [AFAeroMod must be 1 when CavitCheck=true]
False                  Buoyancy    - Include buoyancy effects? (flag)
False                  CompAA      - Flag to compute AeroAcoustics calculation [only used when WakeMod=1 or 2]
AeroAcousticsInput.dat AA_InputFile - AeroAcoustics input file [used only when CompAA=true]
======  Environmental Conditions  ===================================================================
"default"              AirDens     - Air density (kg/m^3)
"default"              KinVisc     - Kinematic air viscosity (m^2/s)
"default"              SpdSound    - Speed of sound (m/s)
"default"              Patm        - Atmospheric pressure (Pa) [used only when CavitCheck=True]
"default"              Pvap        - Vapour pressure of fluid (Pa) [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} [unused when WakeMod=0 or 3]
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 or 3]
True                   TipLoss     - Use the Prandtl tip-loss model? (flag) [unused when WakeMod=0 or 3]
True                   HubLoss     - Use the Prandtl hub-loss model? (flag) [unused when WakeMod=0 or 3]
True                   TanInd      - Include tangential induction in BEMT calculations? (flag) [unused when WakeMod=0 or 3]
True                   AIDrag      - Include the drag term in the axial-induction calculation? (flag) [unused when WakeMod=0 or 3]
True                   TIDrag      - Include the drag term in the tangential-induction calculation? (flag) [unused when WakeMod=0,3 or TanInd=FALSE]
default                IndToler    - Convergence tolerance for BEMT nonlinear solve residual equation {or "default"} (-) [unused when WakeMod=0 or 3]
500                    MaxIter     - Maximum number of iteration steps (-) [unused when WakeMod=0]
======  Dynamic Blade-Element/Momentum Theory Options  ====================================================== [used only when WakeMod=2]
2                      DBEMT_Mod   - Type of dynamic BEMT (DBEMT) model {1=constant tau1, 2=time-dependent tau1} (-) [used only when WakeMod=2]
29.03                  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]
../IEA-15-240-RWT-OLAF/IEA-15-240-RWT_OLAF.dat 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=Minnema/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]
0.1                    UAStartRad  - Starting radius for dynamic stall (fraction of rotor radius) [used only when AFAeroMod=2]
1.0                    UAEndRad    - Ending radius for dynamic stall (fraction of rotor radius) [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)
"IEA-15-240-RWT_AeroDyn15_blade.dat" ADBlFile(1) - Name of file containing distributed aerodynamic properties for Blade #1 (-)
"IEA-15-240-RWT_AeroDyn15_blade.dat" ADBlFile(2) - Name of file containing distributed aerodynamic properties for Blade #2 (-) [unused if NumBl < 2]
"IEA-15-240-RWT_AeroDyn15_blade.dat" ADBlFile(3) - Name of file containing distributed aerodynamic properties for Blade #3 (-) [unused if NumBl < 3]
======  Hub Properties ============================================================================== [used only when Buoyancy=True]
0.0   VolHub             - Hub volume (m^3)
0.0   HubCenBx           - Hub center of buoyancy x direction offset (m)
======  Nacelle Properties ========================================================================== [used only when Buoyancy=True]
0.0   VolNac             - Nacelle volume (m^3)
0,0,0 NacCenB            - Position of nacelle center of buoyancy from yaw bearing in nacelle coordinates (m)
======  Tail fin Aerodynamics ======================================================================== 
False         TFinAero           - Calculate tail fin aerodynamics model (flag)
"unused"      TFinFile           - Input file for tail fin aerodynamics [used only when TFinAero=True]
======  Tower Influence and Aerodynamics ============================================================= [used only when TwrPotent/=0, TwrShadow/=0, or TwrAero=True]
20                     NumTwrNds   - Number of tower nodes used in the analysis  (-) [used only when TwrPotent/=0, TwrShadow/=0, or TwrAero=True]
TwrElev        TwrDiam        TwrCd         TwrTI      TwrCb !TwrTI used only with TwrShadow=2, TwrCb used only with Buoyancy=True
(m)              (m)           (-)           (-)        (-)
  20.000        10.000         0.5           0.1        0.0
  28.000        10.000         0.5           0.1        0.0
  28.001        10.000         0.5           0.1        0.0
  41.000         9.926         0.5           0.1        0.0
  41.001         9.926         0.5           0.1        0.0
  54.000         9.443         0.5           0.1        0.0
  54.001         9.443         0.5           0.1        0.0
  67.000         8.833         0.5           0.1        0.0
  67.001         8.833         0.5           0.1        0.0
  80.000         8.151         0.5           0.1        0.0
  80.001         8.151         0.5           0.1        0.0
  93.000         7.390         0.5           0.1        0.0
  93.001         7.390         0.5           0.1        0.0
 106.000         6.909         0.5           0.1        0.0
 106.001         6.909         0.5           0.1        0.0
 119.000         6.748         0.5           0.1        0.0
 119.001         6.748         0.5           0.1        0.0
 132.000         6.572         0.5           0.1        0.0
 132.001         6.572         0.5           0.1        0.0
 144.386         6.500         0.5           0.1        0.0
======  Outputs  ====================================================================================
False                  SumPrint    - Generate a summary file listing input options and interpolated properties to "<rootname>.AD.sum"?  (flag)
0                      NBlOuts     - Number of blade node outputs [0 - 9] (-)
6, 11, 16, 21, 25, 30, 35, 40, 45 BlOutNd     - Blade nodes whose values will be output  (-)
0                      NTwOuts     - Number of tower node outputs [0 - 9]  (-)
0                      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, (-)
"RtVAvgxh"
"RtArea"
"RtSpeed"
"RtTSR"
END of input file (the word "END" must appear in the first 3 columns of this last OutList line)
====== Outputs for all blade stations (same ending as above for B1N1.... =========================== [optional section]
   0              BldNd_BladesOut     - Number of blades to output all node information at.  Up to number of blades on turbine. (-)
   "All"          BldNd_BlOutNd       - Future feature will allow selecting a portion of the nodes to output.  Not implemented yet. (-)
                  OutList             - The next line(s) contains a list of output parameters.  See OutListParameters.xlsx for a listing of available output channels, (-)
END (the word "END" must appear in the first 3 columns of this last OutList line in the optional nodal output section)

[honorhan]

Does YawBrTDxt represent the fore-aft displacement at the tower top? Did I get that right?

[jjonkman]

Dear @honorhan,

Thanks for clarifying. Are other turbine responses such as rotor speed and blade pitch as you expect them to be for this case?

Yes, YawBrTDxt is the tower-top displacement from ElastoDyn relative to the tower base.

I'm not familiar with the steady-state tower-deflection response as a function of mean wind speed for the IEA Wind 15-MW RWT, but certainly the combination of aerodynamic load, overhanging weight of the RNA and floater motion (if enabled) would all play a role on tower deflection. You could always isolate the contribution of each effect by running separate simulations with distinct functionality enabled/disabled, such as aerodynamic loads, gravity, and tower-base boundary conditions.

Best regards,

[honorhan]

Thank you for your patient reply.