Using Aggregate Mass in ADAMS to Check NREL CS_Monopile.bmi

Dear Jason,

I first used Aggregate Mass in ADAMS to calculate SNL 13.2MW mass moment of inertia and I used the outputs into .bmi file. The results of N.F are quite off from what I got from ADAMS (with only Twr DoFs on).

I then downloaded wind.nrel.gov/public/jjonkman/BModes/
and wind.nrel.gov/public/jjonkman/NR … Bsline5MW/
offshore part to run the Aggregate Mass in ADAMS.

I specified a rigid NRELOffshrBsline5MW_Monopile_RF with all DoFs turning off since I only want to see the mass moment of inertia.
I used FAST 2012Feb edition I believe and thus I delete the line added in the new FAST this year.
I generated ADAMS model and get the mass inertia properties as following:

The aggregate mass in the global reference frame is:
Mass : 3.500003109E+005 kg
Center of Mass :
Location : -0.4106407744, -2.3123880885E-009, 109.5667156223 (meter, meter, meter)
Orientation : 89.9989498566, 5.3861985327, 270.0010456486 (deg)
Mass Inertia Tensor :
IXX : 4.2454591844E+009 kg-meter2
IYY : 4.2253361673E+009 kg-meter
2
IZZ : 2.5520945258E+007 kg-meter2
IXY : 0.2290994561 kg-meter
2
IZX : -1.4007405804E+007 kg-meter2
IYZ : 2.8746322068 kg-meter
2

which I updated your .bmi, the results are quite off again.

Please help me to check I am doing the right thing.

Thanks,

Regards.
Check NREL.zip (108 KB)
BModesJJ.zip (421 KB)

Dear Lingling,

Here are the data I get (calculated by ADAMS) regarding the mass & inertia of the rigid rotor-nacelle assembly (RNA) for the NREL 5-MW turbine:

Mass : 3.500003109E+005 kg
Center of Mass :
Location : -0.4137754432, -8.3126516178E-009, 1.9669893542 (meter, meter, meter)
Orientation : 359.9999911963, 90.0000955298, 354.6136364306 (deg)
Mass Inertia Tensor :
IXX : 4.5050443961E+007 kg-meter2
IYY : 2.4940615741E+007 kg-meter
2
IZZ : 2.5477667652E+007 kg-meter2
IXY : 0.2010825213 kg-meter
2
IZX : 1.4540376371E+006 kg-meter2
IYZ : 2.8803379356 kg-meter
2

The center-of-mass (CM) location, orientation, and inertias above are all relative to FAST’s nacelle coordinate system, which originates at the yaw bearing (i.e., tower top) with “X” pointing downwind, “Y” pointing to the left when looking downwind, and “Z” pointing vertically upwards.

Some of the values you report are close to these; others (especially the Z-coordinate of the CM and the IXX and IYY inertias) are quite a bit different because you’ve output yours relative to the global reference frame.

However, what BModes needs as input is the inertias of the RNA specified relative ot the CM of the RNA. Here are the inertias I report above translated to the CM of the RNA:

Ixx = 4.370E7 kgm^2
Iyy = 2.353E7 kg
m^2
Izz = 2.542E7 kgm^2
Izx = 1.169E6 kg
m^2

See my Nov 23, 2009 post in the forum topic found here for more information: Tower fore-aft modes shapes.

I hope that helps!

Best regards,

Dear Jason,

That is great!

Thanks,

Regards

Dear Jason,

Did you use my uploaded .adm file in ADAMS to get these number? I tried it again and I had these number:

The aggregate mass relative to .NRELOffshrBsline5MW_Monopile_RF_ADAMS.Nacelle_P.NacelleCS_M is:
Mass : 3.500003109E+005 kg
Center of Mass :
Location : -0.4106407744, -2.3123880885E-009, 1.9667156223 (meter, meter, meter)
Orientation : 89.9989498566, 5.3861985327, 270.0010456486 (deg)
Mass Inertia Tensor :
IXX : 4.5106432675E+007 kg-meter2
IYY : 2.4983415493E+007 kg-meter
2
IZZ : 2.5520945258E+007 kg-meter2
IXY : 0.2290994561 kg-meter
2
IZX : 1.4573394965E+006 kg-meter2
IYZ : 2.9617168196 kg-meter
2

And there is an error info showing that “ERROR: The inertia tensor is ill formed. Both the CM/IM orientation and IP will be incorrect.”

Does this mean I have some problem with my model or I did a wrong thing with ADAMS? How can we interpret the orientation of outputs?

Really appreciate,

Regards.

Dear Lingling,

No, I didn’t use your version of the *.adm file. I posted values from an analysis I had run a while ago. However, the results I posted in my Jun 07 post are nearly identical to your results from Jun 08; I suspect that there are only very small differences between our models.

I recall getting that same error about the inertia tensor being ill formed, but don’t remember what caused it. I suggest you ask MSC Technical Support if you are concerned. The results look reasonable to me.

The “Orientation” specifies the 3-1-3 rotational sequence needed to orient the principle axes relative to the inertia frame coordinate system.

I hope that helps.

Best regards,

Dear Jason,

According to the BModes User Manual (authored by Gunjit S. Bir and dated Sept 2007), for example, ixx_tip is “the side-to-side moment of inertia of the tip mass about the tip section x_T reference axis” (Table 2, pp.12) . My interpretation therefore is that the RNA inertia parameters are specified relative to the tower top central point.

However, I came across your June 7th, 2013 post which contradicts the above:

Could you confirm that this is true, in particular for the BModes version which allows a hub_conn=2 boundary condition (downloadable from drive.google.com/drive/folders/ … zksGRnrqxJ)?

Thank you,
Jing

Dear Jing.Li,

I confirm that ixx_tip is the side-to-side inertia about the x axis passing through the center of mass of the rotor-nacelle assembly.

Best regards,

Hi Jason,

Thank you very much for your response!

Best regards,
Jing

Dear Jonkman,

I have reading some tropics in this forum about ADAMSPrep. After reading your reply, I realize the result of Winpac 1.5MW wind turbine by ADAMS in Tower fore-aft modes shapes - #9 by Jason.Jonkman. But if i want to use ADAMS to calculate mass moment of inertia, i have to set ADAMSPrep to 2 or 3 in FAST V7, which dosen’t have NREL 5MW wind turbine modle. In FAST V8 and OPENFAST I have not fine ADAMSPrep switch. So i want to know, did you calculate NREL 5MW’s mass moment of inertia by modeling a new model in ADAMS or in FAST V7?

Best regards :grinning:
Jiantao

Dear @Jiantao.Liu,

We have calculated the mass moment of inertia of the NREL 5-MW baseline wind turbine in ADAMS, but that was many years ago. NREL no longer supports a FAST-to-ADAMS preprocessor and no longer uses ADAMS. There are other ways to calculate the mass moment of inertia apart from ADAMS.

Best regards,

Dear @Jason.Jonkman ,

Thank you very much for your reply! After serching in forum, I found an other way to compute RNA mass inertia in this topic. https://forums.nrel.gov/t/openfast-2nd-order-linearization/2249/2?u=jiantao.liu. And I have some questions about my result, here are my changes in TEST13 of OPENFAST:

  1. In .fst file, I set CompAero and CompInflow to 0, Linearize to True, LinInputs to 2.

  2. In EDFile, I close all DOF except Platform’s six DOF. Set RotSpeed to 0, change tower massden and stiff to a very small value, add platform’s six acceleration in OutList.

  3. In ServoFile, I close PCMode and VSContrl to run LINEARIZATION.

In the topic I mentioned before, you said we can calculate 6x6 rigid-body mass matrix (M) of ElastoDyn by taking the matrix inverse of the 6x6 subset of the input-transmission matrix (D). I try to get D in my .lin file, through head of .lin file, I know the force in platform DOF is loacted between 307-312. So I extract a 6*6 matrix in D, then calculate its inverse matrix. The results are as follows:

M =

   1.0e+07 *

    0.0101    0.0000    0.0000   -0.0000    0.8444   -0.0000
    0.0000    0.0069    0.0000   -0.5776    0.0000   -0.0085
   -0.0001    0.0000    0.0078    0.0000    0.0043   -0.0000
   -0.0000   -0.0101    0.0000    0.8530   -0.0000    0.0123
    0.0147    0.0000    0.0002   -0.0000    1.2393   -0.0000
    0.0000   -0.0001   -0.0000    0.0120    0.0000    0.0031

The linearization of FAST or OpenFAST should have the following form:
MassMatrix

But in my matrix, M(1,1) is different from M(2,2) and M(2,3). I have no idea about this.

I would be appreciate if you can give me some suggestions.

Best regards,
Jiantao

------- OpenFAST example INPUT FILE -------------------------------------------
FAST Certification Test #13: WindPACT 1.5 MW Baseline with many DOFs with VS and VP and FF turbulence.
---------------------- SIMULATION CONTROL --------------------------------------
True          Echo            - Echo input data to <RootName>.ech (flag)
"FATAL"       AbortLevel      - Error level when simulation should abort (string) {"WARNING", "SEVERE", "FATAL"}
         60   TMax            - Total run time (s)
      0.005   DT              - Recommended module time step (s)
          2   InterpOrder     - Interpolation order for input/output time history (-) {1=linear, 2=quadratic}
          0   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}
          0   CompInflow      - Compute inflow wind velocities (switch) {0=still air; 1=InflowWind; 2=external from OpenFOAM}
          0   CompAero        - Compute aerodynamic loads (switch) {0=None; 1=AeroDyn v14; 2=AeroDyn v15}
          0   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; 2=External Platform MCKF}
          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}
---------------------- INPUT FILES ---------------------------------------------
"WP_VSP_WTurb_ElastoDyn.dat"    EDFile          - Name of file containing ElastoDyn input parameters (quoted string)
"unused"      BDBldFile(1)    - Name of file containing BeamDyn input parameters for blade 1 (quoted string)
"unused"      BDBldFile(2)    - Name of file containing BeamDyn input parameters for blade 2 (quoted string)
"unused"      BDBldFile(3)    - Name of file containing BeamDyn input parameters for blade 3 (quoted string)
"WP_Baseline_InflowWind_12mps.dat"    InflowFile      - Name of file containing inflow wind input parameters (quoted string)
"WP_Baseline_AeroDyn15_Dynin.dat"    AeroFile        - Name of file containing aerodynamic input parameters (quoted string)
"WP_VSP_WTurb_ServoDyn.dat"    ServoFile       - Name of file containing control and electrical-drive input parameters (quoted string)
"unused"      HydroFile       - Name of file containing hydrodynamic input parameters (quoted string)
"unused"      SubFile         - Name of file containing sub-structural input parameters (quoted string)
"unused"      MooringFile     - Name of file containing mooring system input parameters (quoted string)
"unused"      IceFile         - Name of file containing ice input parameters (quoted string)
---------------------- OUTPUT --------------------------------------------------
True          SumPrint        - Print summary data to "<RootName>.sum" (flag)
          1   SttsTime        - Amount of time between screen status messages (s)
      99999   ChkptTime       - Amount of time between creating checkpoint files for potential restart (s)
       0.05   DT_Out          - Time step for tabular output (s) (or "default")
          0   TStart          - Time to begin tabular output (s)
          0   OutFileFmt      - Format for tabular (time-marching) output file (switch) {0: uncompressed binary [<RootName>.outb], 1: text file [<RootName>.out], 2: binary file [<RootName>.outb], 3: both 1 and 2}
True          TabDelim        - Use tab delimiters in text tabular output file? (flag) {uses spaces if false}
"ES10.3E2"    OutFmt          - Format used for text tabular output, excluding the time channel.  Resulting field should be 10 characters. (quoted string)
---------------------- LINEARIZATION -------------------------------------------
True         Linearize       - Linearization analysis (flag)
False         CalcSteady      - Calculate a steady-state periodic operating point before linearization? [unused if Linearize=False] (flag)
          3   TrimCase        - Controller parameter to be trimmed {1:yaw; 2:torque; 3:pitch} [used only if CalcSteady=True] (-)
      0.001   TrimTol         - Tolerance for the rotational speed convergence [used only if CalcSteady=True] (-)
       0.01   TrimGain        - Proportional gain for the rotational speed error (>0) [used only if CalcSteady=True] (rad/(rad/s) for yaw or pitch; Nm/(rad/s) for torque)
          0   Twr_Kdmp        - Damping factor for the tower [used only if CalcSteady=True] (N/(m/s))
          0   Bld_Kdmp        - Damping factor for the blades [used only if CalcSteady=True] (N/(m/s))
          2   NLinTimes       - Number of times to linearize (-) [>=1] [unused if Linearize=False]
         30,         60    LinTimes        - List of times at which to linearize (s) [1 to NLinTimes] [used only when Linearize=True and CalcSteady=False]
          2   LinInputs       - Inputs included in linearization (switch) {0=none; 1=standard; 2=all module inputs (debug)} [unused if Linearize=False]
          1   LinOutputs      - Outputs included in linearization (switch) {0=none; 1=from OutList(s); 2=all module outputs (debug)} [unused if Linearize=False]
False         LinOutJac       - Include full Jacobians in linearization output (for debug) (flag) [unused if Linearize=False; used only if LinInputs=LinOutputs=2]
False         LinOutMod       - Write module-level linearization output files in addition to output for full system? (flag) [unused if Linearize=False]
---------------------- VISUALIZATION ------------------------------------------
          0   WrVTK           - VTK visualization data output: (switch) {0=none; 1=initialization data only; 2=animation; 3=mode shapes}
          2   VTK_type        - Type of VTK visualization data: (switch) {1=surfaces; 2=basic meshes (lines/points); 3=all meshes (debug)} [unused if WrVTK=0]
false         VTK_fields      - Write mesh fields to VTK data files? (flag) {true/false} [unused if WrVTK=0]
         15   VTK_fps         - Frame rate for VTK output (frames per second){will use closest integer multiple of DT} [used only if WrVTK=2 or WrVTK=3]

------- ELASTODYN for OpenFAST 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 "<RootName>.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 --------------------------------------
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)
True         PtfmSgDOF   - Platform horizontal surge translation DOF (flag)
True         PtfmSwDOF   - Platform horizontal sway translation DOF (flag)
True         PtfmHvDOF   - Platform vertical heave translation DOF (flag)
True         PtfmRDOF    - Platform roll tilt rotation DOF (flag)
True         PtfmPDOF    - Platform pitch tilt rotation DOF (flag)
True         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)
          0   BlPitch(1)  - Blade 1 initial pitch (degrees)
          0   BlPitch(2)  - Blade 2 initial pitch (degrees)
          0   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)
          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   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 (-)
"../WP_Baseline/Baseline_Blade.dat"    BldFile(1)  - Name of file containing properties for blade 1 (quoted string)
"../WP_Baseline/Baseline_Blade.dat"    BldFile(2)  - Name of file containing properties for blade 2 (quoted string)
"../WP_Baseline/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 ---------------------------------------------------
         10   TwrNodes    - Number of tower nodes used for analysis (-)
"../WP_Baseline/Baseline_Tower.dat"    TwrFile     - Name of file containing tower properties (quoted string)
---------------------- OUTPUT --------------------------------------------------
True          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)
          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] (-)
          4,          7    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] (-)
          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, (-)
"PtfmTAxt"
"PtfmTAyt"
"PtfmTAzt"
"PtfmRAxt"
"PtfmRAyt"
"PtfmRAzt"
END of input file (the word "END" must appear in the first 3 columns of this last OutList line)
---------------------------------------------------------------------------------------

Dear @Jiantao.Liu,

Overall your process sounds OK (please note, though, that you can also disable ServoDyn and there is no reason to change the tower stiffness if you disable the tower DOFs).

Regarding the mass matrix you’ve calculated, are you sure you’ve selected the correct 6x6 sub matrix from the input-transmission (D) matrix? I would also suggest outputting the linearized data with much more precision to ensure that the matrix inverse can be computed accurately. E.g., I would suggest setting OutFmt = “ES20.12E3” in the OpenFAST primary (.fst) input file.

Best regards,

1 Like

Dear @Jason.Jonkman

Thank you very much! I check my procedure, and find the reason. In order to extract sub matrix, I copy input-transmission(D) matrix to EXCEL. EXCEL only keep four significant digits by default settings, which resulting in my wrong result.

Best regards,
Jiantao

1 Like