TwrBsFxt Comparing with wind tunnul(wind load)

Wind & Water Testing
1

Hello eveyone,
i’m studing in master’s degree , i’m going to comparing fast and wind tunnul.but i have a big problem about wind load.
the result between fast and wind tunnul is different,so i’m confuse.
i comparing the CFx , CFy , CMz .
am l have the correct setting in fast?
those are my files.

[1].using Test 21 [5MW]

------- FAST v8.16.* INPUT FILE ------------------------------------------------
FAST Certification Test #21: NREL 5.0 MW Baseline Offshore Turbine with OC4 Jacket Configuration
---------------------- SIMULATION CONTROL --------------------------------------
False Echo - Echo input data to .ech (flag)
“FATAL” AbortLevel - Error level when simulation should abort (string) {“WARNING”, “SEVERE”, “FATAL”}
60 TMax - Total run time (s)
0.001 DT - Recommended module time step (s)
2 InterpOrder - Interpolation order for input/output time history (-) {1=linear, 2=quadratic}
1 NumCrctn - Number of correction iterations (-) {0=explicit calculation, i.e., no corrections}
99999 DT_UJac - Time between calls to get Jacobians (s)
1E+06 UJacSclFact - Scaling factor used in Jacobians (-)
---------------------- FEATURE SWITCHES AND FLAGS ------------------------------
1 CompElast - Compute structural dynamics (switch) {1=ElastoDyn; 2=ElastoDyn + BeamDyn for blades}
1 CompInflow - Compute inflow wind velocities (switch) {0=still air; 1=InflowWind; 2=external from OpenFOAM}
2 CompAero - Compute aerodynamic loads (switch) {0=None; 1=AeroDyn v14; 2=AeroDyn v15}
1 CompServo - Compute control and electrical-drive dynamics (switch) {0=None; 1=ServoDyn}
0 CompHydro - Compute hydrodynamic loads (switch) {0=None; 1=HydroDyn}
0 CompSub - Compute sub-structural dynamics (switch) {0=None; 1=SubDyn}
0 CompMooring - Compute mooring system (switch) {0=None; 1=MAP++; 2=FEAMooring; 3=MoorDyn; 4=OrcaFlex}
0 CompIce - Compute ice loads (switch) {0=None; 1=IceFloe; 2=IceDyn}

[2].NRELOffshrBsline5MW_OC4Jacket_AeroDyn file

--------- AeroDyn v14.04.* INPUT FILE -------------------------------------------------------------------------
NREL 5.0 MW offshore baseline aerodynamic input properties with OC4 jacket tower
“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)
“EQUIL” InfModel - Inflow model [DYNIN or EQUIL] (unquoted string)
“SWIRL” 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)
“NEWTOWER” TwrShad - INSTEAD OF: 0.0 TwrShad - Tower-shadow velocity deficit (-)
True TwrPotent - Calculate tower potential flow (flag) INSTEAD OF 9999.9 ShadHWid - Tower-shadow half width (m)
False TwrShadow - Calculate tower shadow (flag) INSTEAD OF 9999.9 T_Shad_Refpt- Tower-shadow reference point (m)
“NRELOffshrBsline5MW_OC4Jacket_AeroDyn_Tower.dat” TwrFile - Tower drag file name (quoted string)
True CalcTwrAero - Calculate aerodynamic drag of the tower at the ElastoDyn nodes. TwrPotent must be true.
1.225 AirDens - Air density (kg/m^3)
1.464E-05 KinVisc - Kinematic air viscosity [CURRENTLY IGNORED] (m^2/sec)
“DEFAULT” DTAero - Time interval for aerodynamic calculations (sec)
8 NumFoil - Number of airfoil files (-)

[3].NRELOffshrBsline5MW_OC4Jacket_ElastoDyn file

------- ELASTODYN v1.03.* INPUT FILE -------------------------------------------
OC4 TOWER+ 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);
---------------------- 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)
---------------------- 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]
15 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)
-0.00702 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 (-)
63 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)
0 PreCone(1) - Blade 1 cone angle (degrees)
0 PreCone(2) - Blade 2 cone angle (degrees)
0 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)
-5.0191 OverHang - Distance from yaw axis to rotor apex [3 blades] or teeter pin [2 blades] (meters)
1.912 ShftGagL - Distance from rotor apex [3 blades] or teeter pin [2 blades] to shaft strain gages [positive for upwind rotors] (meters)
-5 ShftTilt - Rotor shaft tilt angle (degrees)
1.9 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)
1.75 NacCMzn - Vertical distance from the tower-top to the nacelle CM (meters)
-3.09528 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)
2.23336 NcIMUzn - Vertical distance from the tower-top to the nacelle IMU (meters)
1.96256 Twr2Shft - Vertical distance from the tower-top to the rotor shaft (meters)
88.15 TowerHt - Height of tower above ground level [onshore] or MSL [offshore] (meters)
0 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)
0 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)

[4].NRELOffshrBsline5MW_OC4Jacket_ServoDyn

------- SERVODYN v1.05.* INPUT FILE --------------------------------------------
OC4 Jacket+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);
---------------------- SIMULATION CONTROL --------------------------------------
False Echo - Echo input data to .ech (flag)
“DEFAULT” DT - Communication interval for controllers (s) (or “default”)
---------------------- PITCH CONTROL -------------------------------------------
5 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 TPCOn - Time to enable active pitch control (s) [unused when PCMode=0]
0 TPitManS(1) - Time to start override pitch maneuver for blade 1 and end standard pitch control (s)
0 TPitManS(2) - Time to start override pitch maneuver for blade 2 and end standard pitch control (s)
0 TPitManS(3) - Time to start override pitch maneuver for blade 3 and end standard pitch control (s) [unused for 2 blades]
8 PitManRat(1) - Pitch rate at which override pitch maneuver heads toward final pitch angle for blade 1 (deg/s)
8 PitManRat(2) - Pitch rate at which override pitch maneuver heads toward final pitch angle for blade 2 (deg/s)
8 PitManRat(3) - Pitch rate at which override pitch maneuver heads toward final pitch angle for blade 3 (deg/s) [unused for 2 blades]
90 BlPitchF(1) - Blade 1 final pitch for pitch maneuvers (degrees)
90 BlPitchF(2) - Blade 2 final pitch for pitch maneuvers (degrees)
90 BlPitchF(3) - Blade 3 final pitch for pitch maneuvers (degrees) [unused for 2 blades]
---------------------- GENERATOR AND TORQUE CONTROL ----------------------------
5 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]
94.4 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]
0 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]

and this is my model, i also change the Wind attack angle from 0 degree to 70 degree.
model-來個 PPT 短網址 :: 縮圖剪剪樂!
result-來個 PPT 短網址 :: 縮圖剪剪樂!
am i have the correct setting in fast ?
thank u

2

Dear Li.Kang,

I’m sorry, but I don’t really understand what your question is. Please clarify.

Best regards,

3

i’m going to compare the result between wind tunnul and fast.
but it have a lot of different .for example : in wind attact angle 0 degree the wind tunnul CFx result is 1.5 and FAST is 0.8
the result should be similar , so how can i promote the result in TwrBsFxt in FAST?
did i using the wrong setting. this is my photo of model in wind tunnul-https://ppt.cc/fG9krx
thanks

4

Dear Li.Kang,

Can you clarify what you mean by CFx, CFy, and CMz in your plots? And what do you mean be “wind derection”; is this yaw error?

I gather from your input file that the rotor is parked (not spinning, with blades feathered; is that correct?

It looks like you are using AeroDyn v15 (CompAero = 2), but the AeroDyn input file you’ve shared is for version v14.

Best regards,

5

i’m using the formula CFx=N/(0.5ρU^2A),N= TwrBsFxt force , ρ=Air density , U=wind speed , A=area
of course using the same (0.5ρU^2A) in formula,so the problem is on the N.
yes,the rotor is parked .
my bad ,i past the wrong file .

this is the correct file.

[2] NRELOffshrBsline5MW_OC4Jacket_AeroDyn15

------- AERODYN v15.03.* INPUT FILE ------------------------------------------------
NREL 5.0 MW offshore baseline aerodynamic input properties with OC4 jacket tower
====== General Options ============================================================================
False Echo - Echo the input to “.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 AFAeroMod - Type of blade airfoil aerodynamics model (switch) {1=steady model, 2=Beddoes-Leishman unsteady model}
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)
True TwrAero - Calculate tower aerodynamic loads? (flag)
False FrozenWake - Assume frozen wake during linearization? (flag) [used only when WakeMod=1 and when linearizing]
====== Environmental Conditions ===================================================================
1.225 AirDens - Air density (kg/m^3)
1.464E-05 KinVisc - Kinematic air viscosity (m^2/s)
335 SpdSound - Speed of sound (m/s)
====== 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]
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]
False AIDrag - Include the drag term in the axial-induction calculation? (flag) [used only when WakeMod=1]
False 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]
100 MaxIter - Maximum number of iteration steps (-) [used only when WakeMod=1]
====== Beddoes-Leishman Unsteady Airfoil Aerodynamics Options ===================================== [used only when AFAeroMod=2]
3 UAMod - Unsteady Aero Model Switch (switch) {1=Baseline model (Original), 2=Gonzalez 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]
thanks i preciate

6

Dear Li.Kang,

For a parked rotor, you should disable the wake and unsteady airfoil aerodynamics models, which are only valid for operational conditions. That is, set WakeMod = 0 and AFAeroMod = 1. Do these settings improve the comparison?

So, CFy is based on TwrBsFyt and CMz is based on TwrBsMzt?

And again, is “wind derection” equivalent to yaw error?

How did you derive the lift and drag coefficients you are using for the blades and tower?

Best regards,

7

hello,
i changed WakeMod = 0 and AFAeroMod = 1 , but the force doesn’t have obviosly improve.
yes
yes it is
i don’t really understand , did you mean the “NRELOffshrBsline5MW_OC4Jacket_AeroDyn_Tower” file?

8

Dear Li.Kang,

If I understand correctly, you are modeling a parked rotor with blades feathered at various yaw angles. In such a case, there is no induction, the angle of attack is computed geometrically, and the aerodynamic loads will depend directly on the airfoil data (lift and drag versus angle of attack) that you have specified for the blades and the the tower drag coefficient. My guess there is a mismatch between the airfoil data you have specified in your FAST model and the response of the airfoils used in your wind tunnel test. Solving this issue will likely require a modification of the airfoil data.

Best regards,