Standstill simulation

[honorhan]

Dear Sir or Madam,

I am performing simulations of the IEA 15 MW wind turbine using OpenFAST. For a specific case with a mean wind speed of 10.59 m/s and a turbulence intensity of 20 %, I am investigating a special scenario where the turbine is in a parked condition with the blade pitch angle fixed at 0°. However, from the simulation results, I find that the blade tip flapwise displacement is extremely small. What could be the reason for this?

The input files were modified as follows:
B1TipTDxr：

0 WakeMod - Type of wake/induction model (switch) {0=none, 1=BEMT, 2=DBEMT, 3=OLAF} [WakeMod cannot be
1 AFAeroMod - Type of blade airfoil aerodynamics model (switch) {1=steady model, 2=Beddoes-Leishman unsteady
0 PCMode - Pitch control mode {0: none, 3: user-defined from routine PitchCntrl, 4: user-defined from
0 VSContrl - Variable-speed control mode {0: none, 1: simple VS, 3: user-defined from routine UserVSCont, 4: user-

Best regards

[jjonkman]

Dear @honorhan,

In ElastoDyn, have you disabled GenDOF with RotSpeed = 0 to park the rotor and set the initial blade-pitch angles to zero? What are the deflections of all three blades?

Best regards,

[honorhan]

------- ELASTODYN v1.03.* INPUT FILE -------------------------------------------
IEA 15 MW offshore reference model monopile configuration
---------------------- SIMULATION CONTROL --------------------------------------
False Echo - Echo input data to ".ech" (flag)
3 Method - Integration method: {1: RK4, 2: AB4, or 3: ABM4} (-)
"default" DT Integration time step (s)
---------------------- DEGREES OF FREEDOM --------------------------------------
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]
False DrTrDOF - Drivetrain rotational-flexibility DOF (flag)
False 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)
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 --------------------------------------
0.0 OoPDefl - Initial out-of-plane blade-tip displacement (meters)
0.0 IPDefl - Initial in-plane blade-tip deflection (meters)
0.0 BlPitch(1) - Blade 1 initial pitch (degrees)
0.0 BlPitch(2) - Blade 2 initial pitch (degrees)
0.0 BlPitch(3) - Blade 3 initial pitch (degrees) [unused for 2 blades]
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)
0.0 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)
0.0 PtfmSurge - Initial or fixed horizontal surge translational displacement of platform (meters)
0.0 PtfmSway - Initial or fixed horizontal sway translational displacement of platform (meters)
0.0 PtfmHeave - Initial or fixed vertical heave translational displacement of platform (meters)
0.0 PtfmRoll - Initial or fixed roll tilt rotational displacement of platform (degrees)
0.0 PtfmPitch - Initial or fixed pitch tilt rotational displacement of platform (degrees)
0.0 PtfmYaw - Initial or fixed yaw rotational displacement of platform (degrees)
---------------------- TURBINE CONFIGURATION -----------------------------------
3 NumBl - Number of blades (-)
120.97 TipRad - The distance from the rotor apex to the blade tip (meters)
3.97 HubRad - The distance from the rotor apex to the blade root (meters)
-4.0 PreCone(1) - Blade 1 cone angle (degrees)
-4.0 PreCone(2) - Blade 2 cone angle (degrees)
-4.0 PreCone(3) - Blade 3 cone angle (degrees) [unused for 2 blades]
0.0 HubCM - Distance from rotor apex to hub mass [positive downwind] (meters)
0.0 UndSling - Undersling length [distance from teeter pin to the rotor apex] (meters) [unused for 3 blades]
0.0 Delta3 - Delta-3 angle for teetering rotors (degrees) [unused for 3 blades]
0.0 AzimB1Up - Azimuth value to use for I/O when blade 1 points up (degrees)
-12.097571763912535 OverHang - Distance from yaw axis to rotor apex [3 blades] or teeter pin [2 blades] (meters)
0.0 ShftGagL - Distance from rotor apex [3 blades] or teeter pin [2 blades] to shaft strain gages [positive for upwind rotors] (meters)
-6.0 ShftTilt - Rotor shaft tilt angle (degrees)
-5.125 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)
4.315 NacCMzn - Vertical distance from the tower-top to the nacelle CM (meters)
0.0 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)
0.0 NcIMUzn - Vertical distance from the tower-top to the nacelle IMU (meters)
4.349459414248071 Twr2Shft - Vertical distance from the tower-top to the rotor shaft (meters)
144.386 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)
0.0 PtfmCMxt - Downwind distance from the ground level [onshore] or MSL [offshore] to the platform CM (meters)
0.0 PtfmCMyt - Lateral distance from the ground level [onshore] or MSL [offshore] to the platform CM (meters)
15. PtfmCMzt - Vertical distance from the ground level [onshore] or MSL [offshore] to the platform CM (meters)
15. PtfmRefzt - Vertical distance from the ground level [onshore] or MSL [offshore] to the platform reference point (meters)
---------------------- MASS AND INERTIA ----------------------------------------
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]
69131 HubMass - Hub mass (kg)
969952 HubIner - Hub inertia about rotor axis [3 blades] or teeter axis [2 blades] (kg m^2)
1836784 GenIner - Generator inertia about HSS (kg m^2)
644857 NacMass - Nacelle mass (kg)
32929058 NacYIner - Nacelle inertia about yaw axis (kg m^2)
28249 YawBrMass - Yaw bearing mass (kg)
0.0 PtfmMass - Platform mass (kg)
0.0 PtfmRIner - Platform inertia for roll tilt rotation about the platform CM (kg m^2)
0.0 PtfmPIner - Platform inertia for pitch tilt rotation about the platform CM (kg m^2)
100000000.0 PtfmYIner - Platform inertia for yaw rotation about the platform CM (kg m^2)
---------------------- BLADE ---------------------------------------------------
50 BldNodes - Number of blade nodes (per blade) used for analysis (-)
"IEA-15-240-RWT_ElastoDyn_blade.dat" BldFile1 - Name of file containing properties for blade 1 (quoted string)
"IEA-15-240-RWT_ElastoDyn_blade.dat" BldFile2 - Name of file containing properties for blade 2 (quoted string)
"IEA-15-240-RWT_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]
0.0 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]
---------------------- DRIVETRAIN ----------------------------------------------
100.0 GBoxEff - Gearbox efficiency (%)
1.0 GBRatio - Gearbox ratio (-)
69737644900.0 DTTorSpr - Drivetrain torsional spring (N-m/rad)
49418406.0 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 ---------------------------------------------------
20 TwrNodes - Number of tower nodes used for analysis (-)
"../IEA-15-240-RWT-Monopile/IEA-15-240-RWT-Monopile_ElastoDyn_tower.dat" TwrFile - Name of file containing tower properties (quoted string)
---------------------- OUTPUT --------------------------------------------------
False SumPrint - Print summary data to ".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)
0.0 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]
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] 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"
"BldPitch2"
"BldPitch3"
"GenSpeed"
"RotSpeed"
"RotThrust"
"RotTorq"
"YawBrTDxt"
"YawBrTDyt"
"YawBrTDzt"
END of input file (the word "END" must appear in the first 3 columns of this last OutList line)
---------------------- NODE OUTPUTS --------------------------------------------
0 BldNd_BladesOut - Blades to output
99 BldNd_BlOutNd - Blade nodes on each blade (currently unused)
OutList - The next line(s) contains a list of output parameters. See OutListParameters.xlsx, ElastoDyn_Nodes tab for a listing of available output channels, (-)
"TDx" - local flapwise (translational) deflection (relative to the undeflected position) of node
"TDy" - local edgewise (translational) deflection (relative to the undeflected position) of node
"RDz"
END of input file (the word "END" must appear in the first 3 columns of this last OutList line)

[jjonkman]

Dear @honorhan,

Thanks for clarifying. What are the deflections of the other blades?

I'm not exactly sure what deflection would be expected for this turbine under the conditions you are simulating, but certainly the aerodynamic loads will be less when the rotor is parked than when the rotor is spinning. Does the deflection increase as you increase the mean wind speed, as you'd expect?

Best regards,

[honorhan]

Under the same operating condition, the extreme flapwise displacements of the three blades are all approximately 14 m. However, with a zero pitch angle and in the parked condition, it is unlikely that the flapwise displacements of the three blades would be that small, as shown in the figure above.

[jjonkman]

Dear @honorhan,

Do you mean that when the rotor is operating under the same wind speed, the blade flapwise deflection increases from the 0.75 m you are showing here to 14 m?

For an operating wind turbine, the mean rotor thrust (and blade deflection) will peak at rated wind speed than drop for increasing wind speeds. For a parked rotor with the blades unpitched, the thrust will increase with mean wind seed. Are you seeing that trend when you run separate simulations at different mean wind speeds? How does the rotor thrust compare across these cases?

Best regards,