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

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.

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,

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

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,

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

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

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,

Dear Jason,

Thanks a lot for your time and help…

Sincerely,
Mustafa Vardaroglu