fore-aft and side-to-side accelerations at mid-tower

Wind & Water Computer-Aided Engineering Software Tools
1

Hello to all,
I’m doing a graduate project with FAST v8 on the OC3-Hywind offshore 5MW wind turbine and I need to measure the fore-aft and side-to-side accelerations at mid-tower as outputs. In the output list of FAST calculations, there are “TwHt5ALxt” and “TwHt5ALyt” that correspond to fore-aft and side-to-side acceleration of tower gage 5 (the total number of gages is 9); and I’ve set the ElastoDyn parameters as follows:

---------------------- TOWER ---------------------------------------------------
         9    TwrNodes    - Number of tower nodes used for analysis (-)
"ElastoDyn_Tower.dat"    TwrFile     - Name of file containing tower properties (quoted string)
---------------------- OUTPUT --------------------------------------------------
False         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)
         30   TStart      - Time to begin tabular output (s) (currently unused)
          1   DecFact     - Decimation factor for tabular output {1: output every time step} (-) (currently unused)
          9   NTwGages    - Number of tower nodes that have strain gages for output [0 to 9] (-)
          9   TwrGagNd    - List of tower nodes that have strain gages [1 to TwrNodes] (-) [unused if NTwGages=0]
          1   NBlGages    - Number of blade nodes that have strain gages for output [0 to 9] (-)
          9   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, (-)

also, the NumTwrNds in aerodyn file is 11 (without any change). I get the following error:

FAST_InitializeAll:ED_Init:ED_ReadInput:ReadPrimaryFile:Invalid numerical input for file
".\FastData/ElastoDyn.dat" occurred while trying to read TwrGagNd.
2

Dear Milad,

I see that you have TwrNodes = 9, which means have 9 tower analysis nodes in the calculation. Normally, I’d recommend that TwrNodes be set between 10-20 as a compromise between convergence and computational efficiency; your discretization is a bit coarse.

I also see that you have NTwGages = 9, which means you want to identify 9 of the TwrNodes as output nodes. However, you’ve only identified one of these nodes (node 9) as an output node by setting TwrGagNd = 9. FAST v8 is aborting because when NTwGages = 9, FAST expects 9 entries for TwrGagNd, but you’ve only set 1. For example, if TwrNodes = 19 and NTwGages = 9, you could set TwrGagNd = 2, 4, 6, 8, 10, 12, 14, 16, 18 to assign every other analysis node as an output node. If all you need is to output the acceleration at mid-tower, you can set NTwGages = 1 and TwrGagNd to the analysis node in the middle (for example, if TwrNodes = 9 and NTwGages = 1, you would set TwrGagNd = 5).

Best regards,

3

Dear Dr. Jonkman,

I encounter a strange problem. I am running Test13 and want to output the local force and moments at 50% tower height and blade span. and the output file has showed that these local output are invalid showed below:

I guess there is something wrong with the NTwGages and NBlGages in ElastoDyn input file. But I still cannot figure it out as I think my settings seems to be all right.I have attached my ElastoDyn input file for your reference. Sorry I dont know how to upload the txt file.

------- ELASTODYN v1.03.* INPUT FILE -------------------------------------------
FAST certification Test #13: WindPACT 1.5 MW Baseline with many DOFs with VS and VP and FF turbulence. Model properties from “InputData1.5A08V07adm.xls” (from C. Hansen) with bugs removed.
---------------------- SIMULATION CONTROL --------------------------------------
False Echo - Echo input data to “.ech” (flag)
3 Method - Integration method: {1: RK4, 2: AB4, or 3: ABM4} (-)
0.005 DT - Integration time step (s)
---------------------- ENVIRONMENTAL CONDITION ---------------------------------
9.80665 Gravity - Gravitational acceleration (m/s^2)
---------------------- 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]
True DrTrDOF - Drivetrain rotational-flexibility DOF (flag)
True GenDOF - Generator DOF (flag)
False 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 OoPDefl - Initial out-of-plane blade-tip displacement (meters)
0 IPDefl - Initial in-plane blade-tip deflection (meters)
7.5 BlPitch(1) - Blade 1 initial pitch (degrees)
7.5 BlPitch(2) - Blade 2 initial pitch (degrees)
7.5 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)
20 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 (-)
35 TipRad - The distance from the rotor apex to the blade tip (meters)
1.75 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)
-3.3 OverHang - Distance from yaw axis to rotor apex [3 blades] or teeter pin [2 blades] (meters)
0.99 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)
-0.1449 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)
1.389 NacCMzn - Vertical distance from the tower-top to the nacelle CM (meters)
0 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)
0 NcIMUzn - Vertical distance from the tower-top to the nacelle IMU (meters)
1.61 Twr2Shft - Vertical distance from the tower-top to the rotor shaft (meters)
82.39 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)
---------------------- 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]
15148 HubMass - Hub mass (kg)
34600 HubIner - Hub inertia about rotor axis [3 blades] or teeter axis [2 blades] (kg m^2)
53.036 GenIner - Generator inertia about HSS (kg m^2)
51170 NacMass - Nacelle mass (kg)
49130 NacYIner - Nacelle inertia about yaw axis (kg m^2)
0 YawBrMass - Yaw bearing mass (kg)
0 PtfmMass - Platform mass (kg)
0 PtfmRIner - Platform inertia for roll tilt rotation about the platform CM (kg m^2)
0 PtfmPIner - Platform inertia for pitch tilt rotation about the platform CM (kg m^2)
0 PtfmYIner - Platform inertia for yaw rotation about the platform CM (kg m^2)
---------------------- BLADE ---------------------------------------------------
15 BldNodes - Number of blade nodes (per blade) used for analysis (-)
“Baseline_Blade.dat” BldFile(1) - Name of file containing properties for blade 1 (quoted string)
“Baseline_Blade.dat” BldFile(2) - Name of file containing properties for blade 2 (quoted string)
“Baseline_Blade.dat” BldFile(3) - 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 (%)
87.965 GBRatio - Gearbox ratio (-)
5.6E+09 DTTorSpr - Drivetrain torsional spring (N-m/rad)
1E+07 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 ---------------------------------------------------
11 TwrNodes - Number of tower nodes used for analysis (-)
“Baseline_Tower.dat” TwrFile - Name of file containing tower properties (quoted string)
---------------------- OUTPUT --------------------------------------------------
True 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 TStart - Time to begin tabular output (s) (currently unused)
10 DecFact - Decimation factor for tabular output {1: output every time step} (-) (currently unused)
2 NTwGages - Number of tower nodes that have strain gages for output [0 to 9] (-)
1, 6 TwrGagNd - List of tower nodes that have strain gages [1 to TwrNodes] (-) [unused if NTwGages=0]
1 NBlGages - Number of blade nodes that have strain gages for output [0 to 9] (-)
8 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, (-)
“RotSpeed” - low-speed shaft speed
“GenSpeed” - High-speed shaft speed
“RotPwr” - Rotor power (this is equivalent to the low-speed shaft power)
“RotThrust” - Low-speed shaft thrust force (this is constant along the shaft and is equivalent to the rotor thrust force) (KN)
“BldPitch1” - Blade 1 pitch angle
“BldPitch2” - Blade 2 pitch angle
“BldPitch3” - Blade 3 pitch angle
“TipDzc1” -Blade 1 axial tip deflection (relative to the pitch axis)(m)
“TipDxb1” -Blade 1 flapwise tip deflection (relative to the pitch axis)(m)
“TipDyb1” -Blade 1 edgewise tip deflection (relative to the pitch axis)(m)
“TipDzc2” -Blade 2 axial tip deflection (relative to the pitch axis)(m)
“TipDxb2” -Blade 2 flapwise tip deflection (relative to the pitch axis)(m)
“TipDyb2” -Blade 2 edgewise tip deflection (relative to the pitch axis)(m)
“TipDzc3” -Blade 3 axial tip deflection (relative to the pitch axis)(m)
“TipDxb3” -Blade 3 flapwise tip deflection (relative to the pitch axis)(m)
“TipDyb3” -Blade 3 edgewise tip deflection (relative to the pitch axis)(m)
“RootFzc1” -Blade 1 axial force at the blade root (KN)
“RootFxb1” -Blade 1 flapwise shear force at the blade root(KN)
“RootFyb1” -Blade 1 edgewise shear force at the blade root (KN)
“RootMzc1” -Blade 1 pitching moment at the blade root(kN·m)
“RootMxb1” -Blade 1 edgewise moment (i.e., the moment caused by edgewise forces) at the blade root(kN·m)
“RootMyb1” -Blade 1 flapwise moment (i.e., the moment caused by flapwise forces) at the blade root(kN·m)
“RootFzc1” -Blade 2 axial force at the blade root (KN)
“RootFxb2” -Blade 2 flapwise shear force at the blade root(KN)
“RootFyb2” -Blade 2 edgewise shear force at the blade root (KN)
“RootMzc2” -Blade 2 pitching moment at the blade root(kN·m)
“RootMxb2” -Blade 2 edgewise moment (i.e., the moment caused by edgewise forces) at the blade root(kN·m)
“RootMyb2” -Blade 2 flapwise moment (i.e., the moment caused by flapwise forces) at the blade root(kN·m)
“RootFzc3” -Blade 3 axial force at the blade root (KN)
“RootFxb3” -Blade 3 flapwise shear force at the blade root(KN)
“RootFyb3” -Blade 3 edgewise shear force at the blade root (KN)
“RootMzc3” -Blade 3 pitching moment at the blade root(kN·m)
“RootMxb3” -Blade 3 edgewise moment (i.e., the moment caused by edgewise forces) at the blade root(kN·m)
“RootMyb3” -Blade 3 flapwise moment (i.e., the moment caused by flapwise forces) at the blade root(kN·m)
“YawBrTDxp” -Tower-top / yaw bearing fore-aft (translational) deflection (relative to the undeflected position)(m)
“YawBrTDyp” -Tower-top / yaw bearing side-to-side (translational) deflection (relative to the undeflected position)(m)
“YawBrTDzp” -Tower-top / yaw bearing axial (translational) deflection (relative to the undeflected position)(m)
“YawBrFzp” -Tower-top / yaw bearing axial force Directed along the zn- and zp-axes (kN)
“YawBrFxp” -Tower-top / yaw bearing fore-aft (nonrotating) shear force Directed along the xp-axis (kN)
“YawBrFyp” -Tower-top / yaw bearing side-to-side (nonrotating) shear force Directed along the yp-axis (kN)
“YawBrMzp” -Tower-top / yaw bearing yaw moment About the zn- and zp-axes (kN·m)
“YawBrMxp” -Nonrotating tower-top / yaw bearing roll moment About the xp-axis (kN·m)
“YawBrMyp” -Nonrotating tower-top / yaw bearing pitch moment About the yp-axis (kN·m)
“TwrBsFxt” -Tower base fore-aft shear force
“TwrBsFyt” -Tower base side-to-side shear force
“TwrBsFzt” -Tower base axial force
“TwrBsMxt” -Tower base roll (or side-to-side) moment (i.e., the moment caused by side-to-side forces)
“TwrBsMyt” -Tower base pitching (or fore-aft) moment (i.e., the moment caused by fore-aft forces)
“TwrBsMzt” -Tower base yaw (or torsional) moment
“Spn8FLxb1” -Blade 1 local flapwise shear force at span station 8 Directed along the local xb1-axis (kN)
“Spn8FLyb1” -Blade 1 local edgewise shear force at span station 8 Directed along the local yb1-axis (kN)
“Spn8FLzb1” -Blade 1 local axial force at span station 8 Directed along the local zb1-axis (kN)
“Spn8MLxb1” -Blade 1 local edgewise moment at span station 8 About the local xb1-axis (kN·m)
“Spn8MLyb1” -Blade 1 local flapwise moment at span station 8 About the local yb1-axis (kN·m)
“Spn8MLzb1” -Blade 1 local pitching moment at span station 8 About the local zb1-axis (kN·m)
“Spn8FLxb2” -Blade 2 local flapwise shear force at span station 8 Directed along the local xb2-axis (kN)
“Spn8FLyb2” -Blade 2 local edgewise shear force at span station 8 Directed along the local yb2-axis (kN)
“Spn8FLzb2” -Blade 2 local axial force at span station 8 Directed along the local zb2-axis (kN)
“Spn8MLxb2” -Blade 2 local edgewise moment at span station 8 About the local xb2-axis (kN·m)
“Spn8MLyb2” -Blade 2 local flapwise moment at span station 8 About the local yb2-axis (kN·m)
“Spn8MLzb2” -Blade 2 local pitching moment at span station 8 About the local zb2-axis (kN·m)
“Spn8FLxb3” -Blade 3local flapwise shear force at span station 8 Directed along the local xb3-axis (kN)
“Spn8FLyb3” -Blade 3local edgewise shear force at span station 8 Directed along the local yb3-axis (kN)
“Spn8FLzb3” -Blade 3local axial force at span station 8 Directed along the local zb3-axis (kN)
“Spn8MLxb3” -Blade 3local edgewise moment at span station 8 About the local xb3-axis (kN·m)
“Spn8MLyb3” -Blade 3local flapwise moment at span station 8 About the local yb3-axis (kN·m)
“Spn8MLzb3” -Blade 3local pitching moment at span station 8 About the local zb3-axis (kN·m)
“TwHt6FLxt” - Tower, Gage-6 (Node 4) roll, pitch, and yaw moments
“TwHt6FLyt” - Tower, Gage-6 (Node 4) roll, pitch, and yaw moments
“TwHt6FLzt” - Tower, Gage-6 (Node 4) roll, pitch, and yaw moments
“TwHt6MLxt” - Tower, Gage-6 (Node 4) roll, pitch, and yaw moments
“TwHt6MLyt” - Tower, Gage-6 (Node 4) roll, pitch, and yaw moments
“TwHt6MLzt” - Tower, Gage-6 (Node 4) roll, pitch, and yaw moments

END of input file (the word “END” must appear in the first 3 columns of this last OutList line)

Looking forward to your reply!

Regards,
Charlie

output.PNG
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4

Dear Charlie,

The number in the output name is the output gage number, not the node number. You’ve set NTwGages=2 with TwrGagNd=1,6. Thus, output TwHt1MLxt is the side-to-side moment at node 1, TwHt2MLxt is the side-to-side moment at node 6, and TwHt6MLxt is invalid. Likewise, you’ve set NBlGages=1 with BldGagNd=8. Thus, output Spn1MLxb1 is the edgewise bending moment at node 8 for blade 1 and Spn8MLxb1 is invalid.

Best regards,

5

Dear Dr. Jonkman,

Thanks so much. I always think it may be the problem with the input format in the ElastoDyn file. It seems like a stupid problem. Anyway, always appreciate your help!

Best regards,
Charlie

6

Dear Jason,

I am trying to see the horizontal displacements along the z-axis. “TTDspFA” parameter from ElastoDyn gives the displacement of the tower top, in the fore aft direction.
I am aware that it is possible to get the bending moments along the tower by specifying node numbers to “TwrGagNd” and “NTwGages”.
In a similar way, is it possible to get the horizontal displacements in these nodes?

Sincerely,
Mustafa Vardaroglu

7

Dear Mustafa,

Yes, you can use ElastoDyn outputs TwHtTDxt, TwHtTDyt, and TwHt*TDzt to get the xt, yt, and zt displacements, respectively, at up to 9 output nodes along the tower, where * is between 1 and 9.

Best regards,

8

Dear Jason,

Thanks a lot for your time and help…

Sincerely,
Mustafa Vardaroglu