OC4-Jacket-OWT

Dear Jason,

I am  simulating the offshore wind turbine of Oc4-jacket, I have some questions for the modal analysis, what is the second frequency of the whole system (including the substructure) of Oc4-jacket? If not, can bmodes calculate the second frequency of the whole system?

Looking forward to your reply and thank you for your kindness!

Best regards,
Zhou.Lin

Dear Zhou.Lin,

According to the OC4 Phase I results (nrel.gov/docs/fy12osti/54124.pdf), the second global bending frequency of the tower + jacket of the OC4-jacket is around 1.2 Hz.

BModes can calculate tower natural frequencies, but the jacket must be simplified in BModes as a tower-base boundary condition involving 6x6 mass and stiffness matrices, which can be derived from the SubDyn summary file (hydro_M = MBBt, hydro_K = KBBt, mooring_K = 0).

I hope that helps.

Best regards,

Dear @Jason.Jonkman
For the OC4 jacket model (5MW_OC4Jckt_DLL_WTurb_WavesIrr_MGrowth.fst), could you please tell me where can I obtain more DISTRIBUTED TOWER PROPERTIES information such as “torsion stiffness (TWGJstff)”, “axial stiffness (TwEAStff)”, “fore-aft inertia (TwFAIner)”, “side-to-side inertia (TwSSIner)”. In my understanding these tower section properties must be known and input to BModes to calculate and update the tower mode shapes. However, I cannot find any corresponding information except for TMassDen, TwFAStif, TwSSStif as follows ( from NRELOffshrBsline5MW_OC4Jacket_ElastoDyn_Tower.dat).

------- ELASTODYN V1.00.* TOWER INPUT FILE -------------------------------------
NREL 5.0 MW offshore baseline OC4 tower with flexible Jacket SubStructure (however SS cantilevered at seabed).
---------------------- TOWER PARAMETERS ----------------------------------------
         22   NTwInpSt    - Number of input stations to specify tower geometry
          1   TwrFADmp(1) - Tower 1st fore-aft mode structural damping ratio (%)
          1   TwrFADmp(2) - Tower 2nd fore-aft mode structural damping ratio (%)
          1   TwrSSDmp(1) - Tower 1st side-to-side mode structural damping ratio (%)
          1   TwrSSDmp(2) - Tower 2nd side-to-side mode structural damping ratio (%)
---------------------- TOWER ADJUSTMUNT FACTORS --------------------------------
          1   FAStTunr(1) - Tower fore-aft modal stiffness tuner, 1st mode (-)
          1   FAStTunr(2) - Tower fore-aft modal stiffness tuner, 2nd mode (-)
          1   SSStTunr(1) - Tower side-to-side stiffness tuner, 1st mode (-)
          1   SSStTunr(2) - Tower side-to-side stiffness tuner, 2nd mode (-)
          1   AdjTwMa     - Factor to adjust tower mass density (-)
          1   AdjFASt     - Factor to adjust tower fore-aft stiffness (-)
          1   AdjSSSt     - Factor to adjust tower side-to-side stiffness (-)
---------------------- DISTRIBUTED TOWER PROPERTIES ----------------------------
HtFract    TMassDen      TwFAStif       TwSSStif
 (-)        (kg/m)        (Nm^2)         (Nm^2)
0.000    4900.472786      4.5556E+11     4.5556E+11
0.025    4900.472786      4.4419E+11     4.4419E+11
0.075    4200.272421      4.1707E+11     4.1707E+11
0.125    4057.180384      3.9120E+11     3.9120E+11
0.175    3915.575049      3.6655E+11     3.6655E+11
0.225    3770.476234      3.4234E+11     3.4234E+11
0.275    3626.859482      3.1932E+11     3.1932E+11
0.325    3477.860118      2.9733E+11     2.9733E+11
0.375    3291.027294      2.7214E+11     2.7214E+11
0.425    3102.11339       2.4846E+11     2.4846E+11
0.475    3123.48485       2.2622E+11     2.2622E+11
0.525    2969.643543      2.0732E+11     2.0732E+11
0.575    2639.437112      1.9143E+11     1.9143E+11
0.625    2517.768961      1.7644E+11     1.7644E+11
0.675    2398.659195      1.6232E+11     1.6232E+11
0.725    2282.133754      1.4902E+11     1.4902E+11
0.775    2173.8144        1.3653E+11     1.3653E+11
0.825    2344.181633      1.4213E+11     1.4213E+11
0.875    2687.066514      1.5659E+11     1.5659E+11
0.925    2971.054769      1.6870E+11     1.6870E+11
0.975    3260.985159      1.5955E+11     1.5955E+11
1.000    3260.985159      1.5481E+11     1.5481E+11
---------------------- TOWER FORE-AFT MODE SHAPES ------------------------------
     1.0221    TwFAM1Sh(2) - Mode 1, coefficient of x^2 term
     0.0483    TwFAM1Sh(3) -       , coefficient of x^3 term
    -0.0948    TwFAM1Sh(4) -       , coefficient of x^4 term
     0.2283    TwFAM1Sh(5) -       , coefficient of x^5 term
    -0.2039    TwFAM1Sh(6) -       , coefficient of x^6 term
     0.6197    TwFAM2Sh(2) - Mode 2, coefficient of x^2 term
     0.5380    TwFAM2Sh(3) -       , coefficient of x^3 term
    -0.4478    TwFAM2Sh(4) -       , coefficient of x^4 term
     0.7483    TwFAM2Sh(5) -       , coefficient of x^5 term
    -0.4582    TwFAM2Sh(6) -       , coefficient of x^6 term
---------------------- TOWER SIDE-TO-SIDE MODE SHAPES --------------------------
     1.0034    TwSSM1Sh(2) - Mode 1, coefficient of x^2 term
     0.0700    TwSSM1Sh(3) -       , coefficient of x^3 term
    -0.1377    TwSSM1Sh(4) -       , coefficient of x^4 term
     0.2943    TwSSM1Sh(5) -       , coefficient of x^5 term
    -0.2300    TwSSM1Sh(6) -       , coefficient of x^6 term
     0.5250    TwSSM2Sh(2) - Mode 2, coefficient of x^2 term
     0.6536    TwSSM2Sh(3) -       , coefficient of x^3 term
    -0.6967    TwSSM2Sh(4) -       , coefficient of x^4 term
     1.1231    TwSSM2Sh(5) -       , coefficient of x^5 term
    -0.6049    TwSSM2Sh(6) -       , coefficient of x^6 term

In addition, Is there any other text or supporting document (such as relevant elastodyn.dat & elastodyn_tower.dat) and description corresponding to the following link.
https://openfast.readthedocs.io/en/main/source/user/subdyn/appendixA.html
https://openfast.readthedocs.io/en/main/source/user/subdyn/appendixC.html

Thank you for your assitance and time.
Best regards,

Dear Baoxuan,

Normally, you can assign a very large value for “torsion stiffness (TWGJstff )”, “axial stiffness (TwEAStff )”, and very small value for “fore-aft inertia (TwFAIner )” ,“fore-aft inertia (TwFAIner )”, “side-to-side inertia (TwSSIner )”. It will not influence the results, as discussed in below link.
https://forums.nrel.gov/t/blade-mode-shapes-with-bmodes/1441?u=ran.tu

Dear @Jason.Jonkman ,

I modeled entire tower in Subdyn. When I look through the Subdyn summary file, I am confused by MBBt.

Mass:    3.473670E+05 # Total Mass
CM_point: [   0.000000E+00,   0.000000E+00,   3.818261E+01,] # Center of mass coordinates (Xcm,Ycm,Zcm)
TP_point: [   0.000000E+00,   0.000000E+00,   8.759900E+01,] # Transition piece reference point
MRB: # 6 x 6 Rigid Body Equivalent Mass Matrix w.r.t. (0,0,0).
  - [   3.473670E+05,   0.000000E+00,   0.000000E+00,   0.000000E+00,   1.326338E+07,   0.000000E+00]
  - [   0.000000E+00,   3.473670E+05,   0.000000E+00,  -1.326338E+07,   0.000000E+00,   0.000000E+00]
  - [   0.000000E+00,   0.000000E+00,   3.473670E+05,   0.000000E+00,   0.000000E+00,   0.000000E+00]
  - [   0.000000E+00,  -1.326338E+07,   0.000000E+00,   7.209051E+08,   0.000000E+00,   0.000000E+00]
  - [   1.326338E+07,   0.000000E+00,   0.000000E+00,   0.000000E+00,   7.209051E+08,   0.000000E+00]
  - [   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   2.238086E+06]
M_P: # 6 x 6 Rigid Body Equivalent Mass Matrix w.r.t. TP Ref point
  - [   3.473670E+05,   0.000000E+00,   0.000000E+00,   0.000000E+00,  -1.716562E+07,   0.000000E+00]
  - [   0.000000E+00,   3.473670E+05,   0.000000E+00,   1.716562E+07,   0.000000E+00,   0.000000E+00]
  - [   0.000000E+00,   0.000000E+00,   3.473670E+05,   0.000000E+00,   0.000000E+00,   0.000000E+00]
  - [   0.000000E+00,   1.716562E+07,   0.000000E+00,   1.062738E+09,   0.000000E+00,   0.000000E+00]
  - [  -1.716562E+07,   0.000000E+00,   0.000000E+00,   0.000000E+00,   1.062738E+09,   0.000000E+00]
  - [   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   2.238086E+06]
M_G: # 6 x 6 Rigid Body Equivalent Mass Matrix w.r.t. CM (Xcm,Ycm,Zcm).
  - [   3.473670E+05,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00]
  - [   0.000000E+00,   3.473670E+05,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00]
  - [   0.000000E+00,   0.000000E+00,   3.473670E+05,   0.000000E+00,   0.000000E+00,   0.000000E+00]
  - [   0.000000E+00,   0.000000E+00,   0.000000E+00,   2.144748E+08,   0.000000E+00,   0.000000E+00]
  - [   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   2.144748E+08,   0.000000E+00]
  - [   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   2.238086E+06]
#____________________________________________________________________________________________________
# GUYAN MATRICES at the TP reference point
#____________________________________________________________________________________________________
KBBt: # 6 x 6
  - [   5.045149E+06,   0.000000E+00,   0.000000E+00,   0.000000E+00,  -1.613169E+08,   0.000000E+00]
  - [   0.000000E+00,   5.045149E+06,   0.000000E+00,   1.613169E+08,   0.000000E+00,   0.000000E+00]
  - [   0.000000E+00,   0.000000E+00,   1.062429E+09,   0.000000E+00,   0.000000E+00,   0.000000E+00]
  - [   0.000000E+00,   1.613169E+08,   0.000000E+00,   8.035837E+09,   0.000000E+00,   0.000000E+00]
  - [  -1.613169E+08,   0.000000E+00,   0.000000E+00,   0.000000E+00,   8.035837E+09,   0.000000E+00]
  - [   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   2.214521E+09]
MBBt: # 6 x 6
  - [   8.577564E+04,   0.000000E+00,   0.000000E+00,   0.000000E+00,  -8.880862E+05,   0.000000E+00]
  - [   0.000000E+00,   8.577564E+04,   0.000000E+00,   8.880862E+05,   0.000000E+00,   0.000000E+00]
  - [   0.000000E+00,   0.000000E+00,   7.412644E+04,   0.000000E+00,   0.000000E+00,   0.000000E+00]
  - [   0.000000E+00,   8.880862E+05,   0.000000E+00,   1.142198E+07,   0.000000E+00,   0.000000E+00]
  - [  -8.880862E+05,   0.000000E+00,   0.000000E+00,   0.000000E+00,   1.142198E+07,   0.000000E+00]
  - [   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   2.609863E+05]
  1. I am not using MBBt in BModes. I am just confused what MBBt mean. MBBt seems to be the added mass matrix?

  2. If I used this summary file to BModes (just for example), I want to confirm whether:
    Platform mass inertia 3X3 matrix (i_matrix_pform) should use M_G (4, 4), M_G (5, 5), M_G (6, 6)?

Regards,
Ran

Dear @Ran.Tu,

Thank you for answering @Baoxuan.Wang questions.

Regarding MBBt and KBBt, these are the mass and stiffness matrices associated with the Guyan modes. See the online SubDyn documentation for more information on the Guyan modes and Craig-Bampton reduction used by SubDyn: 4.2.5.6. SubDyn Theory — OpenFAST v3.2.0 documentation.

The platform inertia needed as input to BModes (i_matrix_pform) is the 3x3 inertia matrix relative to the platform center of mass. You can take the lower-right 3x3 submatrix of the rigid body equivalent mass matrix w.r.t. CM from the SubDyn summary file output, i.e., M_G(4:6,4:6).

Best regards,

Dear @Jason.Jonkman ,@Ran.Tu,
Thank you for your replies.This is very helpful.

Dear @Jason.Jonkman
Is there any other text or supporting document (such as relevant elastodyn_tower.dat) and description or more information (such as real soil propertities related to the OC4 Jacket SSI file stiffness matrix) corresponding to the previous links?
https://openfast.readthedocs.io/en/main/source/user/subdyn/appendixC.html
Strangely, tower parameters “TWGJstff ”, “TwEAStff ”, “TwFAIner” ,“TwFAIner ”, “TwSSIner” can be found for other CertTest samples such as OC3 tests and OC4 floating tests, except for OC4 jacket. Therefore, I am worried that I may have missed and neglected some important documents.

Thank you very much.
Best regards

Dear @Baoxuan.Wang,

I’m sorry, but I’m not really sure I understand your question. Please clarify.

Best regards,

Dear @Jason.Jonkman
Sorry.
I mean, have these parameters ( “TWGJstff ”, “TwEAStff ”, “TwFAIner ” ,“TwFAIner ”, “TwSSIner ”) been given for the tower model of oc4 jacket model? I cannot find them in related Technical Report.
For Appendix C. OC4 Jacket SSI Input File, is there any corresponding more description information (such as soil types, soil profile…)?
Best regards,

Dear @Baoxuan.Wang,

You should be able to calculate these sectional properties of the OC4 jacket (if you need them) based on the documented diameter, thickness, and material properties. See the OC4 jacket documentation here: Vorpahl et al. (2013) - OC4 Jacket Model Description.pdf - Google Drive.

This documentation, however, assumes a clamped boundary condition at the seabed. I’m not sure where the data in Appendix C came from. This is a better question for @Emmanuel.Branlard.

Best regards,

Dear Jason.Jonkman
Okay, thank you for your reply.
Best regards.

The data was generated by a former colleague, we are looking into where it might have come from, but it might take some weeks. Sorry about that.

Dear Emmanuel.Branlard
Thank you.
Best regards,

Dear @Jason.Jonkman,

Sorry to bother you again.
According to your previous suggestions, the “torsion stiffness (TWGJstff )”, “axial stiffness (TwEAStff )”, “fore-aft inertia (TwFAIner )”, “side-to-side inertia (TwSSIner )” in DISTRIBUTED TOWER PROPERTIES of OC4Jacket model were set by me as follows

Tower section properties
22        n_secs:     number of tower sections at which properties are specified (-)

sec_loc  str_tw  tw_iner   mass_den  flp_iner  edge_iner  flp_stff   edge_stff   tor_stff   axial_stff  cg_offst  sc_offst tc_offst
(-)      (deg)    (deg)    (kg/m)     (kg-m)    (kg-m)     (Nm^2)     (Nm^2)      (Nm^2)       (N)        (m)       (m)      (m)
0.000     0.0     0.0   4900.472786  1.0E-8   1.0E-8   4.5556E+11  4.5556E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.025     0.0     0.0   4900.472786  1.0E-8   1.0E-8   4.4419E+11  4.4419E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.075     0.0     0.0   4200.272421  1.0E-8   1.0E-8   4.1707E+11  4.1707E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.125     0.0     0.0   4057.180384  1.0E-8   1.0E-8   3.9120E+11  3.9120E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.175     0.0     0.0   3915.575049  1.0E-8   1.0E-8   3.6655E+11  3.6655E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.225     0.0     0.0   3770.476234  1.0E-8   1.0E-8   3.4234E+11  3.4234E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.275     0.0     0.0   3626.859482  1.0E-8   1.0E-8   3.1932E+11  3.1932E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.325     0.0     0.0   3477.860118  1.0E-8   1.0E-8   2.9733E+11  2.9733E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.375     0.0     0.0   3291.027294  1.0E-8   1.0E-8   2.7214E+11  2.7214E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.425     0.0     0.0   3102.11339   1.0E-8   1.0E-8   2.4846E+11  2.4846E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.475     0.0     0.0   3123.48485   1.0E-8   1.0E-8   2.2622E+11  2.2622E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.525     0.0     0.0   2969.643543  1.0E-8   1.0E-8   2.0732E+11  2.0732E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.575     0.0     0.0   2639.437112  1.0E-8   1.0E-8   1.9143E+11  1.9143E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.625     0.0     0.0   2517.768961  1.0E-8   1.0E-8   1.7644E+11  1.7644E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.675     0.0     0.0   2398.659195  1.0E-8   1.0E-8   1.6232E+11  1.6232E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.725     0.0     0.0   2282.133754  1.0E-8   1.0E-8   1.4902E+11  1.4902E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.775     0.0     0.0   2173.8144    1.0E-8   1.0E-8   1.3653E+11  1.3653E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.825     0.0     0.0   2344.181633  1.0E-8   1.0E-8   1.4213E+11  1.4213E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.875     0.0     0.0   2687.066514  1.0E-8   1.0E-8   1.5659E+11  1.5659E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.925     0.0     0.0   2971.054769  1.0E-8   1.0E-8   1.6870E+11  1.6870E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
0.975     0.0     0.0   3260.985159  1.0E-8   1.0E-8   1.5955E+11  1.5955E+11   1.0E+16    1.0E+16      0.0       0.0      0.0
1.000     0.0     0.0   3260.985159  1.0E-8   1.0E-8   1.5481E+11  1.5481E+11   1.0E+16    1.0E+16      0.0       0.0      0.0

**Note: If the above data represents TOWER properties, the following are overwritten:
  str_tw is set to zero
  tw_iner is set to zero
  cg_offst is set to zero
  sc_offst is set to zero
  tc_offst is set to zero
  edge_iner is set equal to flp_iner
  edge_stff is set equal to flp_stff



Then, I run the BModes JJ, and here are the .bmi file: :grinning:



======================   BModes v3.00 Main Input File  ==================
NREL 5MW OC4 Jacket Tower (Rigid foundation) WBX20220902

--------- General parameters ---------------------------------------------------------------------
true      Echo        Echo input file contents to *.echo file if true.
2         beam_type   1: blade, 2: tower (-)
0.        romg:       rotor speed, automatically set to zero for tower modal analysis (rpm)
1.        romg_mult:  rotor speed muliplicative factor (-)
88.15      radius:     rotor tip radius measured along coned blade axis, OR tower height above ground level [onshore] or MSL [offshore](m)
0.0      hub_rad:    hub radius measured along coned blade axis OR tower rigid-base height (m)
0.        precone:    built-in precone angle, automatically set to zero for a tower (deg)
0.        bl_thp:     blade pitch setting, automatically set to zero for a tower (deg)
2         hub_conn:   hub-to-blade or tower-base boundary condition [1: cantilevered; 2: free-free; 3: only axial and torsion constraints] (-)
20        modepr:     number of modes to be printed (-)
t         TabDelim    (true: tab-delimited output tables; false: space-delimited tables)
f         mid_node_tw  (true: output twist at mid-node of elements; false: no mid-node outputs)

--------- Blade-tip or tower-top mass properties --------------------------------------------
3.500003109E+005   tip_mass    blade-tip or tower-top mass (kg)
-0.4137754432      cm_loc      tip-mass c.m. offset from the tower axis measured along x-tower axis (m)
1.9669893542       cm_axial    tip-mass c.m. offset tower tip measures axially along the z axis (m)
4.370E7            ixx_tip     blade lag mass moment of inertia about the tip-section x reference axis (kg-m^2)
2.353E7            iyy_tip     blade flap mass moment of inertia about the tip-section y reference axis (kg-m^2)
2.542E7            izz_tip     torsion mass moment of inertia about the tip-section z reference axis (kg-m^2)
0.                 ixy_tip     cross product of inertia about x and y reference axes(kg-m^2)
1.169E6            izx_tip     cross product of inertia about z and x reference axes(kg-m^2)
0.                 iyz_tip     cross product of inertia about y and z reference axes(kg-m^2)

--------- Distributed-property identifiers --------------------------------------------------------
1         id_mat:     material_type [1: isotropic; non-isotropic composites option not yet available]
'CS_monopile_tower_secs.dat'   : sec_props_file   name of beam section properties file (-)

Property scaling factors..............................
1.0       sec_mass_mult:   mass density multiplier (-)
1.0       flp_iner_mult:   blade flap or tower f-a inertia multiplier (-)
1.0       lag_iner_mult:   blade lag or tower s-s inertia multiplier (-)
1.0       flp_stff_mult:   blade flap or tower f-a bending stiffness multiplier (-)
1.0       edge_stff_mult:  blade lag or tower s-s bending stiffness multiplier (-)
1.0       tor_stff_mult:   torsion stiffness multiplier (-)
1.0       axial_stff_mult: axial stiffness multiplier (-)
1.0       cg_offst_mult:   cg offset multiplier (-)
1.0       sc_offst_mult:   shear center multiplier (-)
1.0       tc_offst_mult:   tension center multiplier (-)

--------- Finite element discretization --------------------------------------------------
50        nselt:     no of blade or tower elements (-)
Distance of element boundary nodes from blade or flexible-tower root (normalized wrt blade or tower length), el_loc()
0.0000	0.0200	0.0400	0.0600	0.0800	0.1000	0.1200	0.1400	0.1600	0.1800	0.2000	0.2200	0.2400	0.2600	0.2800	0.3000	0.3200	0.3400	0.3600	0.3800	0.4000	0.4200	0.4400	0.4600	0.4800	0.5000	0.5200	0.5400	0.5600	0.5800	0.6000	0.6200	0.6400	0.6600	0.6800	0.7000	0.7200	0.7400	0.7600	0.7800	0.8000	0.8200	0.8400	0.8600	0.8800	0.9000	0.9200	0.9400	0.9600	0.9800	1.0000

--------- Properties of tower support subsystem (read only if beam_type is 2) ------------
1          tow_support: : aditional tower support [0: no additional support; 1: floating-platform or monopile with or without tension wires] (-)
-20.15        draft        : depth of tower base from the ground or the MSL (mean sea level) (m)
-18.15    cm_pform     : distance of platform c.m. below the MSL (m)
666000  mass_pform   : platform mass (kg)
Platform mass inertia 3X3 matrix (i_matrix_pform):
6.00288E+06   0.   0.
0.   6.00288E+06   0.
0.   0.   1.02298E+07
-20.15        ref_msl    : distance of platform reference point below the MSL (m)
Platform-reference-point-referred hydrodynamic 6X6 matrix (hydro_M):
 1.811587E+05,  -7.503331E-12,  -4.365575E-11,  -1.249191E-09,  -1.616692E+06,  -5.456968E-10
-5.229595E-12,   1.811587E+05,   1.455192E-11,   1.616692E+06,   2.337401E-10,   1.193257E-09
-3.183231E-11,   1.818989E-12,   1.933164E+05,  -1.236913E-10,  -5.857146E-10,   1.147896E-09
-1.306034E-09,   1.616692E+06,  -1.164153E-10,   2.163200E+07,   1.774606E-08,   1.518492E-08
-1.616692E+06,   2.146407E-10,  -3.492460E-10,   1.680019E-08,   2.163200E+07,   5.820766E-09
-5.820766E-10,   1.135049E-09,   1.243165E-09,   1.458011E-08,   5.848960E-09,   5.716638E+06
Platform-reference-point-referred hydrodynamic 6X6 stiffness matrix (hydro_K):
 8.819354E+07,   2.374873E-08,   2.324581E-06,   1.744088E-05,  -2.231230E+09,   3.308058E-06
-8.428469E-08,   8.819354E+07,  -1.251698E-06,   2.231230E+09,  -6.952323E-06,  -1.952052E-06
 1.423061E-06,  -1.527369E-07,   1.992617E+09,  -6.049871E-06,  -1.603365E-05,  -4.583654E-06
 7.301569E-06,   2.231230E+09,  -7.629395E-06,   1.024845E+11,   1.704693E-05,  -5.130470E-05
-2.231230E+09,  -4.693866E-06,  -7.629395E-06,  -1.016259E-04,   1.024845E+11,  -1.139939E-06
 3.814697E-06,  -2.861023E-06,  -8.999962E-06,  -3.311038E-05,  -6.407499E-06,   8.457470E+09
Mooring-system 6X6 stiffness matrix (mooring_K):
 0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00
 0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00
 0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00
 0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00
 0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00
 0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00,   0.000000E+00

Distributed (hydrodynamic) added-mass per unit length along a flexible portion of the tower length:
0           n_secs_m_distr: number of sections at which added mass per unit length is specified (-)
0.  0.    : z_distr_m [row array of size n_added_m_pts; section locations wrt the flexible tower base over which distributed mass is specified] (m)
0.  0.    : distr_m [row array of size n_added_m_pts; added distributed masses per unit length] (kg/m)

Distributed elastic stiffness per unit length along a flexible portion of the tower length:
0           n_secs_k_distr: number of points at which distributed stiffness per unit length is specified (-)
0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31	32	33	34	35	36  : z_distr_k [row array of size n_added_m_pts; section locations wrt the flexible tower base over which distributed stiffness is specified] (m)
595318000.0 	1165208000	1129400000	1095553000	1059931000	1024493000	989209000	953643000	918718000	883287000	847803000	812541000	777187000	741870000	706616000	671440000	636229000	600957000	565919000	530470000	495081000	459574000	385327000	305479000	280059000	254125000	227500000	200112000	171927000	143115000	114173000	80184000	52237000	35561000	20912000	9000000	1156000   : distr_k [row array of size n_added_m_pts; distributed stiffness per unit length] (N/m^2)

Tension wires data
0         n_attachments: no of wire-attachment locations on tower [0: no tension wires] (-)
3 3       n_wires:       no of wires attached at each location (must be 3 or higher) (-)
6 9       node_attach:   node numbers of attacments location (node number must be more than 1 and less than nselt+2) (-)
0.e0 0.e0 wire_stfness:  wire spring constant in each set (see users' manual) (N/m)
0. 0.     th_wire:       angle of tension wires (wrt the horizontal ground plane) at each attachment point (deg)

END of Main Input File Data *********************************************************************
*************************************************************************************************

Last, I have obtained the modal analysis results as follows: :grinning:

 Running BModes (v1.03.01, 25-Sept-2007, compiled using double precision).
 Linked with the NWTC Subroutine Library (v1.01.08, 26-Sep-2007).

  all parameters checked : o.k.

  ******** modal analysis results **********

      eigenvalue(  1) =  0.368495D+11        mode  1 frequency =      0.319937
      eigenvalue(  2) =  0.374908D+11        mode  2 frequency =      0.322709
      eigenvalue(  3) =  0.483076D+12        mode  3 frequency =      1.158395
      eigenvalue(  4) =  0.514378D+12        mode  4 frequency =      1.195336
      eigenvalue(  5) =  0.186188D+13        mode  5 frequency =      2.274181
      eigenvalue(  6) =  0.218418D+13        mode  6 frequency =      2.463160
      eigenvalue(  7) =  0.319694D+13        mode  7 frequency =      2.979998
      eigenvalue(  8) =  0.162584D+14        mode  8 frequency =      6.720290
      eigenvalue(  9) =  0.180729D+14        mode  9 frequency =      7.085367
      eigenvalue( 10) =  0.564525D+14        mode 10 frequency =     12.522481
      eigenvalue( 11) =  0.576765D+14        mode 11 frequency =     12.657509
      eigenvalue( 12) =  0.166495D+15        mode 12 frequency =     21.505493
      eigenvalue( 13) =  0.168981D+15        mode 13 frequency =     21.665443
      eigenvalue( 14) =  0.523197D+15        mode 14 frequency =     38.122486
      eigenvalue( 15) =  0.526385D+15        mode 15 frequency =     38.238464
      eigenvalue( 16) =  0.135523D+16        mode 16 frequency =     61.355680
      eigenvalue( 17) =  0.135901D+16        mode 17 frequency =     61.441292
      eigenvalue( 18) =  0.292881D+16        mode 18 frequency =     90.197394
      eigenvalue( 19) =  0.293304D+16        mode 19 frequency =     90.262635
      eigenvalue( 20) =  0.566409D+16        mode 20 frequency =    125.433587

 BModes terminated normally.

However, to my surprise, the content (especially for s-s disp).out file that BModes created is strange, and I cannot distinguish the tower modes, as we can see as follows :sob:

Results generated by BModes (v1.03.01, 25-Sept-2007, compiled using double precision) on 02-Sep-2022 at 15:30:40.
NREL 5MW OC4 Jacket Tower (Rigid foundation) WBX20220902                                           
=================================================================================

            tower frequencies & mode shapes
            --- only first  20 modes printed


 -------- Mode No.   1  (freq = 0.319937E+00 Hz)

span_loc	s-s disp	s-s slope	f-a disp	f-a slope	twist

 0.0000	 0.000003	 0.000007	-0.015808	-0.033785	 0.000000
 0.0200	 0.000004	 0.000008	-0.016516	-0.036987	 0.000000
 0.0400	 0.000004	 0.000009	-0.017287	-0.040190	 0.000000
 0.0600	 0.000004	 0.000010	-0.018124	-0.043405	 0.000000
 0.0800	 0.000004	 0.000010	-0.019024	-0.046632	 0.000000
 0.1000	 0.000004	 0.000011	-0.019989	-0.049869	 0.000000
 0.1200	 0.000005	 0.000012	-0.021019	-0.053116	 0.000000
 0.1400	 0.000005	 0.000012	-0.022114	-0.056373	 0.000000
 0.1600	 0.000005	 0.000013	-0.023274	-0.059637	 0.000000
 0.1800	 0.000005	 0.000014	-0.024500	-0.062908	 0.000000
 0.2000	 0.000006	 0.000015	-0.025791	-0.066186	 0.000000
 0.2200	 0.000006	 0.000015	-0.027148	-0.069471	 0.000000
 0.2400	 0.000006	 0.000016	-0.028570	-0.072763	 0.000000
 0.2600	 0.000007	 0.000017	-0.030059	-0.076058	 0.000000
 0.2800	 0.000007	 0.000018	-0.031613	-0.079358	 0.000000
 0.3000	 0.000007	 0.000018	-0.033233	-0.082658	 0.000000
 0.3200	 0.000008	 0.000019	-0.034920	-0.085959	 0.000000
 0.3400	 0.000008	 0.000020	-0.036672	-0.089265	 0.000000
 0.3600	 0.000009	 0.000020	-0.038491	-0.092586	 0.000000
 0.3800	 0.000009	 0.000021	-0.040376	-0.095925	 0.000000
 0.4000	 0.000009	 0.000022	-0.042328	-0.099278	 0.000000
 0.4200	 0.000010	 0.000023	-0.044348	-0.102644	 0.000000
 0.4400	 0.000010	 0.000023	-0.046434	-0.106022	 0.000000
 0.4600	 0.000011	 0.000024	-0.048589	-0.109407	 0.000000
 0.4800	 0.000011	 0.000025	-0.050811	-0.112801	 0.000000
 0.5000	 0.000012	 0.000026	-0.053101	-0.116189	 0.000000
 0.5200	 0.000012	 0.000026	-0.055459	-0.119567	 0.000000
 0.5400	 0.000013	 0.000027	-0.057884	-0.122928	 0.000000
 0.5600	 0.000013	 0.000028	-0.060376	-0.126258	 0.000000
 0.5800	 0.000014	 0.000029	-0.062935	-0.129554	 0.000000
 0.6000	 0.000015	 0.000029	-0.065559	-0.132810	 0.000000
 0.6200	 0.000015	 0.000030	-0.068247	-0.136023	 0.000000
 0.6400	 0.000016	 0.000031	-0.070999	-0.139189	 0.000000
 0.6600	 0.000016	 0.000031	-0.073815	-0.142300	 0.000000
 0.6800	 0.000017	 0.000032	-0.076691	-0.145354	 0.000000
 0.7000	 0.000018	 0.000033	-0.079629	-0.148342	 0.000000
 0.7200	 0.000018	 0.000033	-0.082625	-0.151259	 0.000000
 0.7400	 0.000019	 0.000034	-0.085679	-0.154100	 0.000000
 0.7600	 0.000020	 0.000035	-0.088789	-0.156854	 0.000000
 0.7800	 0.000020	 0.000035	-0.091953	-0.159517	 0.000000
 0.8000	 0.000021	 0.000036	-0.095168	-0.161981	 0.000000
 0.8200	 0.000022	 0.000036	-0.098430	-0.164221	 0.000000
 0.8400	 0.000023	 0.000037	-0.101735	-0.166232	 0.000000
 0.8600	 0.000023	 0.000037	-0.105078	-0.167992	 0.000000
 0.8800	 0.000024	 0.000038	-0.108453	-0.169522	 0.000000
 0.9000	 0.000025	 0.000038	-0.111857	-0.170845	 0.000000
 0.9200	 0.000026	 0.000038	-0.115286	-0.171976	 0.000000
 0.9400	 0.000026	 0.000038	-0.118735	-0.172941	 0.000000
 0.9600	 0.000027	 0.000038	-0.122202	-0.173776	 0.000000
 0.9800	 0.000028	 0.000039	-0.125685	-0.174478	 0.000000
 1.0000	 0.000029	 0.000039	-0.129181	-0.175043	 0.000000


 -------- Mode No.   2  (freq = 0.322709E+00 Hz)

span_loc	s-s disp	s-s slope	f-a disp	f-a slope	twist

 0.0000	 0.000000	 0.000000	-0.016010	-0.034140	 0.000000
 0.0200	 0.000000	 0.000000	-0.016725	-0.037359	 0.000000
 0.0400	 0.000000	 0.000000	-0.017504	-0.040578	 0.000000
 0.0600	 0.000000	 0.000000	-0.018348	-0.043809	 0.000000
 0.0800	 0.000000	 0.000000	-0.019257	-0.047050	 0.000000
 0.1000	 0.000000	 0.000000	-0.020231	-0.050301	 0.000000
 0.1200	 0.000000	 0.000000	-0.021269	-0.053561	 0.000000
 0.1400	 0.000000	 0.000000	-0.022373	-0.056829	 0.000000
 0.1600	 0.000000	 0.000000	-0.023543	-0.060102	 0.000000
 0.1800	 0.000000	 0.000000	-0.024778	-0.063382	 0.000000
 0.2000	 0.000000	 0.000000	-0.026078	-0.066667	 0.000000
 0.2200	 0.000000	 0.000000	-0.027445	-0.069959	 0.000000
 0.2400	 0.000000	 0.000000	-0.028877	-0.073255	 0.000000
 0.2600	 0.000000	 0.000000	-0.030375	-0.076553	 0.000000
 0.2800	 0.000000	 0.000000	-0.031940	-0.079853	 0.000000
 0.3000	 0.000000	 0.000000	-0.033570	-0.083153	 0.000000
 0.3200	 0.000000	 0.000000	-0.035266	-0.086452	 0.000000
 0.3400	 0.000000	 0.000000	-0.037028	-0.089752	 0.000000
 0.3600	 0.000000	 0.000000	-0.038857	-0.093067	 0.000000
 0.3800	 0.000000	 0.000000	-0.040751	-0.096397	 0.000000
 0.4000	 0.000000	 0.000000	-0.042713	-0.099739	 0.000000
 0.4200	 0.000000	 0.000000	-0.044741	-0.103090	 0.000000
 0.4400	 0.000000	 0.000000	-0.046837	-0.106452	 0.000000
 0.4600	 0.000000	 0.000000	-0.049000	-0.109818	 0.000000
 0.4800	 0.000000	 0.000000	-0.051230	-0.113189	 0.000000
 0.5000	 0.000000	 0.000000	-0.053528	-0.116551	 0.000000
 0.5200	 0.000000	 0.000000	-0.055893	-0.119899	 0.000000
 0.5400	 0.000000	 0.000000	-0.058324	-0.123228	 0.000000
 0.5600	 0.000000	 0.000000	-0.060822	-0.126520	 0.000000
 0.5800	 0.000000	 0.000000	-0.063385	-0.129776	 0.000000
 0.6000	 0.000000	 0.000000	-0.066013	-0.132987	 0.000000
 0.6200	 0.000000	 0.000000	-0.068704	-0.136151	 0.000000
 0.6400	 0.000000	 0.000000	-0.071459	-0.139263	 0.000000
 0.6600	 0.000000	 0.000000	-0.074275	-0.142316	 0.000000
 0.6800	 0.000000	 0.000000	-0.077151	-0.145306	 0.000000
 0.7000	 0.000000	 0.000000	-0.080087	-0.148225	 0.000000
 0.7200	 0.000000	 0.000000	-0.083080	-0.151067	 0.000000
 0.7400	 0.000000	 0.000000	-0.086129	-0.153826	 0.000000
 0.7600	 0.000000	 0.000000	-0.089233	-0.156493	 0.000000
 0.7800	 0.000000	 0.000000	-0.092389	-0.159061	 0.000000
 0.8000	 0.000000	 0.000000	-0.095594	-0.161429	 0.000000
 0.8200	 0.000000	 0.000000	-0.098844	-0.163569	 0.000000
 0.8400	 0.000000	 0.000000	-0.102135	-0.165479	 0.000000
 0.8600	 0.000000	 0.000000	-0.105462	-0.167139	 0.000000
 0.8800	 0.000000	 0.000000	-0.108819	-0.168570	 0.000000
 0.9000	 0.000000	 0.000000	-0.112203	-0.169793	 0.000000
 0.9200	 0.000000	 0.000000	-0.115609	-0.170825	 0.000000
 0.9400	 0.000000	 0.000000	-0.119035	-0.171690	 0.000000
 0.9600	 0.000000	 0.000000	-0.122476	-0.172420	 0.000000
 0.9800	 0.000000	 0.000000	-0.125931	-0.173011	 0.000000
 1.0000	 0.000000	 0.000000	-0.129396	-0.173460	 0.000000


 -------- Mode No.   3  (freq = 0.115839E+01 Hz)

span_loc	s-s disp	s-s slope	f-a disp	f-a slope	twist

 0.0000	 0.000049	 0.000061	-0.061002	-0.075311	 0.000003
 0.0200	 0.000050	 0.000058	-0.062478	-0.072218	 0.000003
 0.0400	 0.000051	 0.000055	-0.063890	-0.068966	 0.000003
 0.0600	 0.000052	 0.000053	-0.065235	-0.065544	 0.000003
 0.0800	 0.000053	 0.000050	-0.066510	-0.061951	 0.000003
 0.1000	 0.000054	 0.000047	-0.067711	-0.058185	 0.000003
 0.1200	 0.000055	 0.000044	-0.068836	-0.054247	 0.000003
 0.1400	 0.000056	 0.000040	-0.069880	-0.050135	 0.000003
 0.1600	 0.000057	 0.000037	-0.070840	-0.045849	 0.000003
 0.1800	 0.000058	 0.000033	-0.071712	-0.041388	 0.000003
 0.2000	 0.000058	 0.000030	-0.072494	-0.036751	 0.000003
 0.2200	 0.000059	 0.000026	-0.073181	-0.031936	 0.000003
 0.2400	 0.000059	 0.000022	-0.073769	-0.026942	 0.000003
 0.2600	 0.000060	 0.000017	-0.074257	-0.021772	 0.000003
 0.2800	 0.000060	 0.000013	-0.074639	-0.016423	 0.000003
 0.3000	 0.000060	 0.000009	-0.074912	-0.010898	 0.000003
 0.3200	 0.000060	 0.000004	-0.075073	-0.005197	 0.000003
 0.3400	 0.000060	-0.000001	-0.075118	 0.000690	 0.000003
 0.3600	 0.000060	-0.000005	-0.075043	 0.006785	 0.000003
 0.3800	 0.000060	-0.000011	-0.074844	 0.013097	 0.000003
 0.4000	 0.000060	-0.000016	-0.074517	 0.019621	 0.000003
 0.4200	 0.000059	-0.000021	-0.074057	 0.026362	 0.000003
 0.4400	 0.000059	-0.000027	-0.073460	 0.033323	 0.000003
 0.4600	 0.000058	-0.000033	-0.072722	 0.040500	 0.000003
 0.4800	 0.000058	-0.000038	-0.071838	 0.047900	 0.000003
 0.5000	 0.000057	-0.000045	-0.070804	 0.055498	 0.000003
 0.5200	 0.000056	-0.000051	-0.069616	 0.063287	 0.000003
 0.5400	 0.000055	-0.000057	-0.068270	 0.071259	 0.000003
 0.5600	 0.000054	-0.000064	-0.066764	 0.079383	 0.000003
 0.5800	 0.000052	-0.000070	-0.065093	 0.087659	 0.000003
 0.6000	 0.000051	-0.000077	-0.063255	 0.096076	 0.000003
 0.6200	 0.000049	-0.000084	-0.061248	 0.104633	 0.000003
 0.6400	 0.000047	-0.000091	-0.059068	 0.113324	 0.000003
 0.6600	 0.000046	-0.000098	-0.056713	 0.122140	 0.000003
 0.6800	 0.000044	-0.000105	-0.054181	 0.131079	 0.000003
 0.7000	 0.000041	-0.000113	-0.051468	 0.140129	 0.000003
 0.7200	 0.000039	-0.000120	-0.048574	 0.149286	 0.000003
 0.7400	 0.000037	-0.000127	-0.045495	 0.158545	 0.000003
 0.7600	 0.000034	-0.000135	-0.042230	 0.167892	 0.000003
 0.7800	 0.000031	-0.000142	-0.038778	 0.177325	 0.000003
 0.8000	 0.000028	-0.000150	-0.035140	 0.186471	 0.000003
 0.8200	 0.000025	-0.000157	-0.031322	 0.195213	 0.000003
 0.8400	 0.000022	-0.000163	-0.027335	 0.203507	 0.000003
 0.8600	 0.000019	-0.000170	-0.023187	 0.211229	 0.000003
 0.8800	 0.000015	-0.000175	-0.018890	 0.218416	 0.000003
 0.9000	 0.000012	-0.000181	-0.014454	 0.225134	 0.000003
 0.9200	 0.000008	-0.000186	-0.009888	 0.231418	 0.000003
 0.9400	 0.000004	-0.000191	-0.005200	 0.237365	 0.000003
 0.9600	 0.000000	-0.000195	-0.000394	 0.243204	 0.000003
 0.9800	-0.000004	-0.000200	 0.004528	 0.248928	 0.000003
 1.0000	-0.000008	-0.000204	 0.009563	 0.254536	 0.000003


 -------- Mode No.   4  (freq = 0.119534E+01 Hz)

span_loc	s-s disp	s-s slope	f-a disp	f-a slope	twist

 0.0000	 0.000000	 0.000000	-0.062548	-0.074677	 0.000000
 0.0200	 0.000000	 0.000000	-0.064003	-0.070852	 0.000000
 0.0400	 0.000000	 0.000000	-0.065380	-0.066877	 0.000000
 0.0600	 0.000000	 0.000000	-0.066677	-0.062740	 0.000000
 0.0800	 0.000000	 0.000000	-0.067889	-0.058440	 0.000000
 0.1000	 0.000000	 0.000000	-0.069013	-0.053978	 0.000000
 0.1200	 0.000000	 0.000000	-0.070046	-0.049354	 0.000000
 0.1400	 0.000000	 0.000000	-0.070985	-0.044569	 0.000000
 0.1600	 0.000000	 0.000000	-0.071827	-0.039626	 0.000000
 0.1800	 0.000000	 0.000000	-0.072569	-0.034524	 0.000000
 0.2000	 0.000000	 0.000000	-0.073207	-0.029264	 0.000000
 0.2200	 0.000000	 0.000000	-0.073738	-0.023845	 0.000000
 0.2400	 0.000000	 0.000000	-0.074159	-0.018268	 0.000000
 0.2600	 0.000000	 0.000000	-0.074467	-0.012538	 0.000000
 0.2800	 0.000000	 0.000000	-0.074659	-0.006655	 0.000000
 0.3000	 0.000000	 0.000000	-0.074732	-0.000625	 0.000000
 0.3200	 0.000000	 0.000000	-0.074683	 0.005552	 0.000000
 0.3400	 0.000000	 0.000000	-0.074508	 0.011881	 0.000000
 0.3600	 0.000000	 0.000000	-0.074205	 0.018386	 0.000000
 0.3800	 0.000000	 0.000000	-0.073771	 0.025071	 0.000000
 0.4000	 0.000000	 0.000000	-0.073201	 0.031929	 0.000000
 0.4200	 0.000000	 0.000000	-0.072492	 0.038960	 0.000000
 0.4400	 0.000000	 0.000000	-0.071640	 0.046163	 0.000000
 0.4600	 0.000000	 0.000000	-0.070643	 0.053530	 0.000000
 0.4800	 0.000000	 0.000000	-0.069497	 0.061064	 0.000000
 0.5000	 0.000000	 0.000000	-0.068199	 0.068734	 0.000000
 0.5200	 0.000000	 0.000000	-0.066746	 0.076529	 0.000000
 0.5400	 0.000000	 0.000000	-0.065136	 0.084437	 0.000000
 0.5600	 0.000000	 0.000000	-0.063367	 0.092419	 0.000000
 0.5800	 0.000000	 0.000000	-0.061438	 0.100472	 0.000000
 0.6000	 0.000000	 0.000000	-0.059347	 0.108580	 0.000000
 0.6200	 0.000000	 0.000000	-0.057093	 0.116736	 0.000000
 0.6400	 0.000000	 0.000000	-0.054676	 0.124928	 0.000000
 0.6600	 0.000000	 0.000000	-0.052095	 0.133140	 0.000000
 0.6800	 0.000000	 0.000000	-0.049350	 0.141365	 0.000000
 0.7000	 0.000000	 0.000000	-0.046440	 0.149584	 0.000000
 0.7200	 0.000000	 0.000000	-0.043365	 0.157785	 0.000000
 0.7400	 0.000000	 0.000000	-0.040128	 0.165955	 0.000000
 0.7600	 0.000000	 0.000000	-0.036727	 0.174071	 0.000000
 0.7800	 0.000000	 0.000000	-0.033164	 0.182125	 0.000000
 0.8000	 0.000000	 0.000000	-0.029444	 0.189791	 0.000000
 0.8200	 0.000000	 0.000000	-0.025576	 0.196975	 0.000000
 0.8400	 0.000000	 0.000000	-0.021569	 0.203645	 0.000000
 0.8600	 0.000000	 0.000000	-0.017435	 0.209709	 0.000000
 0.8800	 0.000000	 0.000000	-0.013185	 0.215211	 0.000000
 0.9000	 0.000000	 0.000000	-0.008831	 0.220209	 0.000000
 0.9200	 0.000000	 0.000000	-0.004381	 0.224739	 0.000000
 0.9400	 0.000000	 0.000000	 0.000156	 0.228880	 0.000000
 0.9600	 0.000000	 0.000000	 0.004773	 0.232788	 0.000000
 0.9800	 0.000000	 0.000000	 0.009466	 0.236454	 0.000000
 1.0000	 0.000000	 0.000000	 0.014230	 0.239871	 0.000000


 -------- Mode No.   5  (freq = 0.227418E+01 Hz)

span_loc	s-s disp	s-s slope	f-a disp	f-a slope	twist

 0.0000	 0.000000	 0.000000	-0.022541	 0.011866	-0.000024
 0.0200	 0.000000	 0.000000	-0.022196	 0.022614	-0.000024
 0.0400	 0.000000	 0.000000	-0.021637	 0.033121	-0.000024
 0.0600	 0.000000	 0.000000	-0.020871	 0.043401	-0.000024
 0.0800	 0.000000	 0.000000	-0.019902	 0.053433	-0.000024
 0.1000	 0.000000	 0.000000	-0.018735	 0.063188	-0.000024
 0.1200	 0.000000	 0.000000	-0.017376	 0.072641	-0.000024
 0.1400	 0.000000	-0.000001	-0.015831	 0.081767	-0.000024
 0.1600	 0.000000	-0.000001	-0.014107	 0.090533	-0.000024
 0.1800	 0.000000	-0.000001	-0.012211	 0.098915	-0.000024
 0.2000	 0.000000	-0.000001	-0.010152	 0.106883	-0.000024
 0.2200	 0.000000	-0.000001	-0.007938	 0.114409	-0.000024
 0.2400	 0.000000	-0.000001	-0.005578	 0.121461	-0.000024
 0.2600	 0.000000	-0.000001	-0.003083	 0.128004	-0.000024
 0.2800	 0.000000	-0.000001	-0.000461	 0.134005	-0.000024
 0.3000	 0.000000	-0.000001	 0.002274	 0.139427	-0.000024
 0.3200	 0.000000	-0.000001	 0.005112	 0.144235	-0.000024
 0.3400	 0.000000	-0.000001	 0.008040	 0.148397	-0.000024
 0.3600	 0.000000	-0.000001	 0.011044	 0.151888	-0.000024
 0.3800	 0.000000	-0.000001	 0.014111	 0.154661	-0.000024
 0.4000	 0.000000	-0.000001	 0.017226	 0.156666	-0.000024
 0.4200	 0.000000	-0.000001	 0.020372	 0.157849	-0.000024
 0.4400	 0.000000	-0.000001	 0.023534	 0.158156	-0.000024
 0.4600	 0.000000	-0.000001	 0.026692	 0.157529	-0.000024
 0.4800	 0.000000	-0.000001	 0.029828	 0.155908	-0.000024
 0.5000	 0.000000	-0.000001	 0.032921	 0.153237	-0.000024
 0.5200	 0.000000	-0.000001	 0.035950	 0.149461	-0.000024
 0.5400	 0.000000	-0.000001	 0.038892	 0.144523	-0.000024
 0.5600	 0.000000	-0.000001	 0.041722	 0.138386	-0.000024
 0.5800	 0.000000	-0.000001	 0.044418	 0.130991	-0.000024
 0.6000	 0.000000	-0.000001	 0.046952	 0.122286	-0.000024
 0.6200	 0.000000	-0.000001	 0.049299	 0.112211	-0.000024
 0.6400	 0.000000	-0.000001	 0.051430	 0.100703	-0.000024
 0.6600	 0.000000	-0.000001	 0.053316	 0.087708	-0.000024
 0.6800	 0.000000	-0.000001	 0.054926	 0.073150	-0.000024
 0.7000	 0.000000	-0.000001	 0.056229	 0.056971	-0.000024
 0.7200	 0.000000	 0.000000	 0.057192	 0.039098	-0.000024
 0.7400	 0.000000	 0.000000	 0.057779	 0.019449	-0.000024
 0.7600	 0.000000	 0.000000	 0.057955	-0.002037	-0.000024
 0.7800	 0.000000	 0.000000	 0.057682	-0.025461	-0.000024
 0.8000	 0.000000	 0.000000	 0.056930	-0.049935	-0.000024
 0.8200	 0.000000	 0.000000	 0.055682	-0.075091	-0.000024
 0.8400	 0.000000	 0.000000	 0.053925	-0.100719	-0.000024
 0.8600	 0.000000	 0.000001	 0.051657	-0.126303	-0.000024
 0.8800	 0.000000	 0.000001	 0.048877	-0.151816	-0.000024
 0.9000	 0.000000	 0.000001	 0.045587	-0.177346	-0.000024
 0.9200	 0.000000	 0.000001	 0.041785	-0.202902	-0.000024
 0.9400	 0.000000	 0.000001	 0.037470	-0.228779	-0.000024
 0.9600	 0.000000	 0.000001	 0.032624	-0.255960	-0.000024
 0.9800	 0.000000	 0.000001	 0.027220	-0.284481	-0.000024
 1.0000	 0.000000	 0.000002	 0.021233	-0.314400	-0.000024

This does not seem reasonable, so does it mean that there are still problems with the DISTRIBUTED TOWER PROPERTIES file?
Thank you in advance.
Best Regards,

Dear @Baoxuan.Wang,

From my quick review of your input files, I see a couple potential issues:

  • Your tower support subsystem (jacket mass and stiffness) are located at about 20 m above MSL, but your tower base is located at MSL. You should set hub_rad = 20.15 m.

  • I’m concerned that your tor_stff and axial_stff are several orders magnitude larger than the flap_stff and edge_stff; this will likely cause problems with BModes’ eigensolver. I would recommend using at most two orders of magnitude larger when you are trying to eliminate the torsional and axial contribution to the modes.

Best regards,

Dear Jason,

If hub_rad is the tower base height, and draft is also the depth of tower base from MSL/ground. The sign of these two varibles are opposite.
But it seems both hub_rad and draft define the same thing–I mean tower base height from MSL/ground. So I can not understand why it needs to be defined twice.

Regards
Ran

Dear @Jason.Jonkman,
This is also a question I want to ask. My understanding is that the rigid-base height for tower is usually set to 0, as mentioned in “OC3Hywind_tower_secs.dat” and the previous post file “BModes.txt”.

Best regards,

Dear @Baoxuan.Wang and @Ran.Tu,

Good point. I think I made a mistake. It seems that BModes inputs hub_rad and draft are redundant. I was thinking that they are both defined relative to MSL (with hub_rad positive upward and draft positive downward), but looking again at my OC3-Hywind model, it seems that the hub_rad is measured relative to the elevation defined by draft. Unfortunately, I can’t find good documentation for this.

Best regards,

Dear @Jason.Jonkman,
Thank you for your reply and constant assistance.
According to your advice, I modified the DISTRIBUTED TOWER PROPERTIES file again.

Tower section properties
22        n_secs:     number of tower sections at which properties are specified (-)

sec_loc  str_tw  tw_iner   mass_den  flp_iner  edge_iner  flp_stff   edge_stff   tor_stff   axial_stff  cg_offst  sc_offst tc_offst
(-)      (deg)    (deg)    (kg/m)     (kg-m)    (kg-m)     (Nm^2)     (Nm^2)      (Nm^2)       (N)        (m)       (m)      (m)
0.000     0.0     0.0   4900.472786  10   10   4.5556E+11  4.5556E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.025     0.0     0.0   4900.472786  10   10   4.4419E+11  4.4419E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.075     0.0     0.0   4200.272421  10   10   4.1707E+11  4.1707E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.125     0.0     0.0   4057.180384  10   10   3.9120E+11  3.9120E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.175     0.0     0.0   3915.575049  10   10   3.6655E+11  3.6655E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.225     0.0     0.0   3770.476234  10   10   3.4234E+11  3.4234E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.275     0.0     0.0   3626.859482  10   10   3.1932E+11  3.1932E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.325     0.0     0.0   3477.860118  10   10   2.9733E+11  2.9733E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.375     0.0     0.0   3291.027294  10   10   2.7214E+11  2.7214E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.425     0.0     0.0   3102.11339   10   10   2.4846E+11  2.4846E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.475     0.0     0.0   3123.48485   10   10   2.2622E+11  2.2622E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.525     0.0     0.0   2969.643543  10   10   2.0732E+11  2.0732E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.575     0.0     0.0   2639.437112  10   10   1.9143E+11  1.9143E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.625     0.0     0.0   2517.768961  10   10   1.7644E+11  1.7644E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.675     0.0     0.0   2398.659195  10   10   1.6232E+11  1.6232E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.725     0.0     0.0   2282.133754  10   10   1.4902E+11  1.4902E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.775     0.0     0.0   2173.8144    10   10   1.3653E+11  1.3653E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.825     0.0     0.0   2344.181633  10   10   1.4213E+11  1.4213E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.875     0.0     0.0   2687.066514  10   10   1.5659E+11  1.5659E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.925     0.0     0.0   2971.054769  10   10   1.6870E+11  1.6870E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
0.975     0.0     0.0   3260.985159  10   10   1.5955E+11  1.5955E+11   5.0E+11    5.0E+11      0.0       0.0      0.0
1.000     0.0     0.0   3260.985159  10   10   1.5481E+11  1.5481E+11   5.0E+11    5.0E+11      0.0       0.0      0.0

**Note: If the above data represents TOWER properties, the following are overwritten:
  str_tw is set to zero
  tw_iner is set to zero
  cg_offst is set to zero
  sc_offst is set to zero
  tc_offst is set to zero
  edge_iner is set equal to flp_iner
  edge_stff is set equal to flp_stff

and then I obtained this, which seems more right:

Results generated by BModes (v1.03.01, 25-Sept-2007, compiled using double precision) on 02-Sep-2022 at 23:29:11.
NREL 5MW OC4 Jacket Tower (Rigid foundation) WBX20220902                                           
=================================================================================

            tower frequencies & mode shapes
            --- only first  20 modes printed


 -------- Mode No.   1  (freq = 0.319914E+00 Hz)

span_loc	s-s disp	s-s slope	f-a disp	f-a slope	twist

 0.0000	-0.015806	-0.033781	 0.000000	 0.000000	 0.000755
 0.0200	-0.016514	-0.036983	 0.000000	 0.000000	 0.000772
 0.0400	-0.017286	-0.040186	 0.000000	 0.000000	 0.000789
 0.0600	-0.018121	-0.043400	 0.000000	 0.000000	 0.000806
 0.0800	-0.019022	-0.046627	 0.000000	 0.000000	 0.000824
 0.1000	-0.019987	-0.049864	 0.000000	 0.000000	 0.000841
 0.1200	-0.021017	-0.053111	 0.000000	 0.000000	 0.000858
 0.1400	-0.022112	-0.056368	 0.000000	 0.000000	 0.000875
 0.1600	-0.023272	-0.059631	 0.000000	 0.000000	 0.000893
 0.1800	-0.024497	-0.062902	 0.000000	 0.000000	 0.000910
 0.2000	-0.025788	-0.066180	 0.000000	 0.000000	 0.000927
 0.2200	-0.027145	-0.069465	 0.000000	 0.000000	 0.000944
 0.2400	-0.028567	-0.072756	 0.000000	 0.000000	 0.000961
 0.2600	-0.030055	-0.076051	 0.000000	 0.000000	 0.000979
 0.2800	-0.031610	-0.079350	 0.000000	 0.000000	 0.000996
 0.3000	-0.033230	-0.082651	 0.000000	 0.000000	 0.001013
 0.3200	-0.034916	-0.085952	 0.000000	 0.000000	 0.001030
 0.3400	-0.036668	-0.089257	 0.000000	 0.000000	 0.001048
 0.3600	-0.038487	-0.092578	 0.000000	 0.000000	 0.001065
 0.3800	-0.040372	-0.095917	 0.000000	 0.000000	 0.001082
 0.4000	-0.042324	-0.099269	 0.000000	 0.000000	 0.001099
 0.4200	-0.044343	-0.102635	 0.000000	 0.000000	 0.001117
 0.4400	-0.046430	-0.106013	 0.000000	 0.000000	 0.001134
 0.4600	-0.048584	-0.109398	 0.000000	 0.000000	 0.001151
 0.4800	-0.050806	-0.112792	 0.000000	 0.000000	 0.001168
 0.5000	-0.053096	-0.116180	 0.000000	 0.000000	 0.001185
 0.5200	-0.055454	-0.119557	 0.000000	 0.000000	 0.001203
 0.5400	-0.057879	-0.122918	 0.000000	 0.000000	 0.001220
 0.5600	-0.060371	-0.126248	 0.000000	 0.000000	 0.001237
 0.5800	-0.062929	-0.129544	 0.000000	 0.000000	 0.001254
 0.6000	-0.065552	-0.132800	 0.000000	 0.000000	 0.001272
 0.6200	-0.068241	-0.136013	 0.000000	 0.000000	 0.001289
 0.6400	-0.070993	-0.139179	 0.000000	 0.000000	 0.001306
 0.6600	-0.073808	-0.142290	 0.000000	 0.000000	 0.001323
 0.6800	-0.076684	-0.145344	 0.000000	 0.000000	 0.001340
 0.7000	-0.079622	-0.148332	 0.000000	 0.000000	 0.001358
 0.7200	-0.082618	-0.151249	 0.000000	 0.000000	 0.001375
 0.7400	-0.085671	-0.154089	 0.000000	 0.000000	 0.001392
 0.7600	-0.088781	-0.156843	 0.000000	 0.000000	 0.001409
 0.7800	-0.091945	-0.159506	 0.000000	 0.000000	 0.001427
 0.8000	-0.095160	-0.161971	 0.000000	 0.000000	 0.001444
 0.8200	-0.098422	-0.164211	 0.000000	 0.000000	 0.001461
 0.8400	-0.101727	-0.166222	 0.000000	 0.000000	 0.001478
 0.8600	-0.105069	-0.167982	 0.000000	 0.000000	 0.001496
 0.8800	-0.108444	-0.169512	 0.000000	 0.000000	 0.001513
 0.9000	-0.111848	-0.170835	 0.000000	 0.000000	 0.001530
 0.9200	-0.115276	-0.171966	 0.000000	 0.000000	 0.001547
 0.9400	-0.118725	-0.172931	 0.000000	 0.000000	 0.001564
 0.9600	-0.122193	-0.173767	 0.000000	 0.000000	 0.001582
 0.9800	-0.125675	-0.174469	 0.000000	 0.000000	 0.001599
 1.0000	-0.129170	-0.175034	 0.000000	 0.000000	 0.001616


 -------- Mode No.   2  (freq = 0.322715E+00 Hz)

span_loc	s-s disp	s-s slope	f-a disp	f-a slope	twist

 0.0000	 0.000000	 0.000000	-0.016010	-0.034140	 0.000000
 0.0200	 0.000000	 0.000000	-0.016725	-0.037359	 0.000000
 0.0400	 0.000000	 0.000000	-0.017505	-0.040579	 0.000000
 0.0600	 0.000000	 0.000000	-0.018349	-0.043809	 0.000000
 0.0800	 0.000000	 0.000000	-0.019257	-0.047051	 0.000000
 0.1000	 0.000000	 0.000000	-0.020231	-0.050302	 0.000000
 0.1200	 0.000000	 0.000000	-0.021270	-0.053562	 0.000000
 0.1400	 0.000000	 0.000000	-0.022374	-0.056829	 0.000000
 0.1600	 0.000000	 0.000000	-0.023543	-0.060103	 0.000000
 0.1800	 0.000000	 0.000000	-0.024778	-0.063383	 0.000000
 0.2000	 0.000000	 0.000000	-0.026079	-0.066668	 0.000000
 0.2200	 0.000000	 0.000000	-0.027445	-0.069959	 0.000000
 0.2400	 0.000000	 0.000000	-0.028878	-0.073256	 0.000000
 0.2600	 0.000000	 0.000000	-0.030376	-0.076554	 0.000000
 0.2800	 0.000000	 0.000000	-0.031940	-0.079854	 0.000000
 0.3000	 0.000000	 0.000000	-0.033570	-0.083154	 0.000000
 0.3200	 0.000000	 0.000000	-0.035267	-0.086453	 0.000000
 0.3400	 0.000000	 0.000000	-0.037029	-0.089753	 0.000000
 0.3600	 0.000000	 0.000000	-0.038857	-0.093068	 0.000000
 0.3800	 0.000000	 0.000000	-0.040752	-0.096398	 0.000000
 0.4000	 0.000000	 0.000000	-0.042714	-0.099740	 0.000000
 0.4200	 0.000000	 0.000000	-0.044742	-0.103091	 0.000000
 0.4400	 0.000000	 0.000000	-0.046838	-0.106453	 0.000000
 0.4600	 0.000000	 0.000000	-0.049001	-0.109818	 0.000000
 0.4800	 0.000000	 0.000000	-0.051231	-0.113190	 0.000000
 0.5000	 0.000000	 0.000000	-0.053529	-0.116552	 0.000000
 0.5200	 0.000000	 0.000000	-0.055893	-0.119900	 0.000000
 0.5400	 0.000000	 0.000000	-0.058325	-0.123228	 0.000000
 0.5600	 0.000000	 0.000000	-0.060823	-0.126521	 0.000000
 0.5800	 0.000000	 0.000000	-0.063386	-0.129776	 0.000000
 0.6000	 0.000000	 0.000000	-0.066014	-0.132988	 0.000000
 0.6200	 0.000000	 0.000000	-0.068705	-0.136152	 0.000000
 0.6400	 0.000000	 0.000000	-0.071460	-0.139263	 0.000000
 0.6600	 0.000000	 0.000000	-0.074276	-0.142316	 0.000000
 0.6800	 0.000000	 0.000000	-0.077152	-0.145306	 0.000000
 0.7000	 0.000000	 0.000000	-0.080088	-0.148224	 0.000000
 0.7200	 0.000000	 0.000000	-0.083081	-0.151066	 0.000000
 0.7400	 0.000000	 0.000000	-0.086130	-0.153825	 0.000000
 0.7600	 0.000000	 0.000000	-0.089234	-0.156492	 0.000000
 0.7800	 0.000000	 0.000000	-0.092390	-0.159061	 0.000000
 0.8000	 0.000000	 0.000000	-0.095595	-0.161428	 0.000000
 0.8200	 0.000000	 0.000000	-0.098845	-0.163568	 0.000000
 0.8400	 0.000000	 0.000000	-0.102136	-0.165478	 0.000000
 0.8600	 0.000000	 0.000000	-0.105462	-0.167138	 0.000000
 0.8800	 0.000000	 0.000000	-0.108820	-0.168568	 0.000000
 0.9000	 0.000000	 0.000000	-0.112204	-0.169791	 0.000000
 0.9200	 0.000000	 0.000000	-0.115610	-0.170823	 0.000000
 0.9400	 0.000000	 0.000000	-0.119035	-0.171687	 0.000000
 0.9600	 0.000000	 0.000000	-0.122477	-0.172417	 0.000000
 0.9800	 0.000000	 0.000000	-0.125931	-0.173009	 0.000000
 1.0000	 0.000000	 0.000000	-0.129396	-0.173457	 0.000000


 -------- Mode No.   3  (freq = 0.115832E+01 Hz)

span_loc	s-s disp	s-s slope	f-a disp	f-a slope	twist

 0.0000	-0.060838	-0.075116	 0.000000	 0.000000	-0.005031
 0.0200	-0.062310	-0.072033	 0.000000	 0.000000	-0.005135
 0.0400	-0.063718	-0.068792	 0.000000	 0.000000	-0.005240
 0.0600	-0.065060	-0.065382	 0.000000	 0.000000	-0.005344
 0.0800	-0.066332	-0.061800	 0.000000	 0.000000	-0.005448
 0.1000	-0.067531	-0.058047	 0.000000	 0.000000	-0.005552
 0.1200	-0.068653	-0.054122	 0.000000	 0.000000	-0.005656
 0.1400	-0.069694	-0.050022	 0.000000	 0.000000	-0.005760
 0.1600	-0.070652	-0.045751	 0.000000	 0.000000	-0.005865
 0.1800	-0.071523	-0.041304	 0.000000	 0.000000	-0.005969
 0.2000	-0.072303	-0.036682	 0.000000	 0.000000	-0.006073
 0.2200	-0.072988	-0.031882	 0.000000	 0.000000	-0.006177
 0.2400	-0.073576	-0.026904	 0.000000	 0.000000	-0.006281
 0.2600	-0.074063	-0.021749	 0.000000	 0.000000	-0.006385
 0.2800	-0.074444	-0.016417	 0.000000	 0.000000	-0.006490
 0.3000	-0.074718	-0.010909	 0.000000	 0.000000	-0.006594
 0.3200	-0.074879	-0.005226	 0.000000	 0.000000	-0.006698
 0.3400	-0.074925	 0.000643	 0.000000	 0.000000	-0.006802
 0.3600	-0.074851	 0.006719	 0.000000	 0.000000	-0.006906
 0.3800	-0.074654	 0.013012	 0.000000	 0.000000	-0.007011
 0.4000	-0.074329	 0.019516	 0.000000	 0.000000	-0.007115
 0.4200	-0.073871	 0.026236	 0.000000	 0.000000	-0.007219
 0.4400	-0.073277	 0.033176	 0.000000	 0.000000	-0.007323
 0.4600	-0.072542	 0.040331	 0.000000	 0.000000	-0.007427
 0.4800	-0.071661	 0.047709	 0.000000	 0.000000	-0.007531
 0.5000	-0.070631	 0.055284	 0.000000	 0.000000	-0.007636
 0.5200	-0.069448	 0.063050	 0.000000	 0.000000	-0.007740
 0.5400	-0.068107	 0.070998	 0.000000	 0.000000	-0.007844
 0.5600	-0.066606	 0.079098	 0.000000	 0.000000	-0.007948
 0.5800	-0.064941	 0.087349	 0.000000	 0.000000	-0.008052
 0.6000	-0.063110	 0.095741	 0.000000	 0.000000	-0.008157
 0.6200	-0.061110	 0.104272	 0.000000	 0.000000	-0.008261
 0.6400	-0.058937	 0.112938	 0.000000	 0.000000	-0.008365
 0.6600	-0.056591	 0.121727	 0.000000	 0.000000	-0.008469
 0.6800	-0.054067	 0.130640	 0.000000	 0.000000	-0.008573
 0.7000	-0.051363	 0.139663	 0.000000	 0.000000	-0.008677
 0.7200	-0.048478	 0.148793	 0.000000	 0.000000	-0.008782
 0.7400	-0.045410	 0.158025	 0.000000	 0.000000	-0.008886
 0.7600	-0.042156	 0.167343	 0.000000	 0.000000	-0.008990
 0.7800	-0.038714	 0.176749	 0.000000	 0.000000	-0.009094
 0.8000	-0.035088	 0.185868	 0.000000	 0.000000	-0.009198
 0.8200	-0.031283	 0.194584	 0.000000	 0.000000	-0.009302
 0.8400	-0.027308	 0.202854	 0.000000	 0.000000	-0.009407
 0.8600	-0.023173	 0.210552	 0.000000	 0.000000	-0.009511
 0.8800	-0.018890	 0.217718	 0.000000	 0.000000	-0.009615
 0.9000	-0.014469	 0.224417	 0.000000	 0.000000	-0.009719
 0.9200	-0.009917	 0.230682	 0.000000	 0.000000	-0.009823
 0.9400	-0.005244	 0.236611	 0.000000	 0.000000	-0.009928
 0.9600	-0.000453	 0.242432	 0.000000	 0.000000	-0.010032
 0.9800	 0.004453	 0.248139	 0.000000	 0.000000	-0.010136
 1.0000	 0.009472	 0.253731	 0.000000	 0.000000	-0.010240


 -------- Mode No.   4  (freq = 0.119523E+01 Hz)

span_loc	s-s disp	s-s slope	f-a disp	f-a slope	twist

 0.0000	 0.000000	 0.000000	-0.062543	-0.074679	 0.000000
 0.0200	 0.000000	 0.000000	-0.063999	-0.070856	 0.000000
 0.0400	 0.000000	 0.000000	-0.065376	-0.066883	 0.000000
 0.0600	 0.000000	 0.000000	-0.066672	-0.062748	 0.000000
 0.0800	 0.000000	 0.000000	-0.067885	-0.058450	 0.000000
 0.1000	 0.000000	 0.000000	-0.069009	-0.053990	 0.000000
 0.1200	 0.000000	 0.000000	-0.070043	-0.049369	 0.000000
 0.1400	 0.000000	 0.000000	-0.070982	-0.044586	 0.000000
 0.1600	 0.000000	 0.000000	-0.071825	-0.039645	 0.000000
 0.1800	 0.000000	 0.000000	-0.072567	-0.034544	 0.000000
 0.2000	 0.000000	 0.000000	-0.073205	-0.029286	 0.000000
 0.2200	 0.000000	 0.000000	-0.073736	-0.023868	 0.000000
 0.2400	 0.000000	 0.000000	-0.074158	-0.018293	 0.000000
 0.2600	 0.000000	 0.000000	-0.074467	-0.012565	 0.000000
 0.2800	 0.000000	 0.000000	-0.074659	-0.006684	 0.000000
 0.3000	 0.000000	 0.000000	-0.074732	-0.000655	 0.000000
 0.3200	 0.000000	 0.000000	-0.074684	 0.005521	 0.000000
 0.3400	 0.000000	 0.000000	-0.074510	 0.011849	 0.000000
 0.3600	 0.000000	 0.000000	-0.074208	 0.018353	 0.000000
 0.3800	 0.000000	 0.000000	-0.073774	 0.025036	 0.000000
 0.4000	 0.000000	 0.000000	-0.073204	 0.031893	 0.000000
 0.4200	 0.000000	 0.000000	-0.072496	 0.038923	 0.000000
 0.4400	 0.000000	 0.000000	-0.071646	 0.046125	 0.000000
 0.4600	 0.000000	 0.000000	-0.070649	 0.053492	 0.000000
 0.4800	 0.000000	 0.000000	-0.069504	 0.061026	 0.000000
 0.5000	 0.000000	 0.000000	-0.068206	 0.068696	 0.000000
 0.5200	 0.000000	 0.000000	-0.066754	 0.076491	 0.000000
 0.5400	 0.000000	 0.000000	-0.065145	 0.084399	 0.000000
 0.5600	 0.000000	 0.000000	-0.063377	 0.092381	 0.000000
 0.5800	 0.000000	 0.000000	-0.061448	 0.100435	 0.000000
 0.6000	 0.000000	 0.000000	-0.059358	 0.108545	 0.000000
 0.6200	 0.000000	 0.000000	-0.057105	 0.116701	 0.000000
 0.6400	 0.000000	 0.000000	-0.054689	 0.124895	 0.000000
 0.6600	 0.000000	 0.000000	-0.052109	 0.133109	 0.000000
 0.6800	 0.000000	 0.000000	-0.049364	 0.141336	 0.000000
 0.7000	 0.000000	 0.000000	-0.046454	 0.149558	 0.000000
 0.7200	 0.000000	 0.000000	-0.043381	 0.157761	 0.000000
 0.7400	 0.000000	 0.000000	-0.040143	 0.165935	 0.000000
 0.7600	 0.000000	 0.000000	-0.036743	 0.174055	 0.000000
 0.7800	 0.000000	 0.000000	-0.033180	 0.182112	 0.000000
 0.8000	 0.000000	 0.000000	-0.029461	 0.189783	 0.000000
 0.8200	 0.000000	 0.000000	-0.025593	 0.196971	 0.000000
 0.8400	 0.000000	 0.000000	-0.021586	 0.203646	 0.000000
 0.8600	 0.000000	 0.000000	-0.017452	 0.209716	 0.000000
 0.8800	 0.000000	 0.000000	-0.013202	 0.215222	 0.000000
 0.9000	 0.000000	 0.000000	-0.008847	 0.220225	 0.000000
 0.9200	 0.000000	 0.000000	-0.004396	 0.224761	 0.000000
 0.9400	 0.000000	 0.000000	 0.000141	 0.228907	 0.000000
 0.9600	 0.000000	 0.000000	 0.004759	 0.232821	 0.000000
 0.9800	 0.000000	 0.000000	 0.009452	 0.236493	 0.000000
 1.0000	 0.000000	 0.000000	 0.014217	 0.239916	 0.000000


 -------- Mode No.   5  (freq = 0.184094E+01 Hz)

span_loc	s-s disp	s-s slope	f-a disp	f-a slope	twist

 0.0000	-0.000332	-0.000073	 0.000000	 0.000000	 0.068533
 0.0200	-0.000332	 0.000029	 0.000000	 0.000000	 0.069712
 0.0400	-0.000331	 0.000131	 0.000000	 0.000000	 0.070890
 0.0600	-0.000327	 0.000231	 0.000000	 0.000000	 0.072069
 0.0800	-0.000321	 0.000331	 0.000000	 0.000000	 0.073248
 0.1000	-0.000314	 0.000430	 0.000000	 0.000000	 0.074427
 0.1200	-0.000304	 0.000527	 0.000000	 0.000000	 0.075606
 0.1400	-0.000293	 0.000624	 0.000000	 0.000000	 0.076785
 0.1600	-0.000279	 0.000719	 0.000000	 0.000000	 0.077963
 0.1800	-0.000264	 0.000812	 0.000000	 0.000000	 0.079142
 0.2000	-0.000247	 0.000904	 0.000000	 0.000000	 0.080321
 0.2200	-0.000228	 0.000993	 0.000000	 0.000000	 0.081500
 0.2400	-0.000207	 0.001080	 0.000000	 0.000000	 0.082679
 0.2600	-0.000185	 0.001165	 0.000000	 0.000000	 0.083858
 0.2800	-0.000160	 0.001247	 0.000000	 0.000000	 0.085036
 0.3000	-0.000135	 0.001326	 0.000000	 0.000000	 0.086215
 0.3200	-0.000107	 0.001401	 0.000000	 0.000000	 0.087394
 0.3400	-0.000079	 0.001474	 0.000000	 0.000000	 0.088573
 0.3600	-0.000048	 0.001542	 0.000000	 0.000000	 0.089752
 0.3800	-0.000017	 0.001608	 0.000000	 0.000000	 0.090930
 0.4000	 0.000016	 0.001669	 0.000000	 0.000000	 0.092109
 0.4200	 0.000050	 0.001726	 0.000000	 0.000000	 0.093288
 0.4400	 0.000085	 0.001778	 0.000000	 0.000000	 0.094467
 0.4600	 0.000121	 0.001825	 0.000000	 0.000000	 0.095646
 0.4800	 0.000158	 0.001866	 0.000000	 0.000000	 0.096825
 0.5000	 0.000195	 0.001901	 0.000000	 0.000000	 0.098003
 0.5200	 0.000234	 0.001930	 0.000000	 0.000000	 0.099182
 0.5400	 0.000273	 0.001951	 0.000000	 0.000000	 0.100361
 0.5600	 0.000312	 0.001965	 0.000000	 0.000000	 0.101540
 0.5800	 0.000351	 0.001971	 0.000000	 0.000000	 0.102719
 0.6000	 0.000391	 0.001969	 0.000000	 0.000000	 0.103897
 0.6200	 0.000430	 0.001958	 0.000000	 0.000000	 0.105076
 0.6400	 0.000469	 0.001938	 0.000000	 0.000000	 0.106255
 0.6600	 0.000507	 0.001908	 0.000000	 0.000000	 0.107434
 0.6800	 0.000545	 0.001868	 0.000000	 0.000000	 0.108613
 0.7000	 0.000582	 0.001818	 0.000000	 0.000000	 0.109791
 0.7200	 0.000618	 0.001756	 0.000000	 0.000000	 0.110970
 0.7400	 0.000652	 0.001682	 0.000000	 0.000000	 0.112149
 0.7600	 0.000685	 0.001597	 0.000000	 0.000000	 0.113328
 0.7800	 0.000716	 0.001498	 0.000000	 0.000000	 0.114507
 0.8000	 0.000745	 0.001391	 0.000000	 0.000000	 0.115685
 0.8200	 0.000771	 0.001276	 0.000000	 0.000000	 0.116864
 0.8400	 0.000796	 0.001155	 0.000000	 0.000000	 0.118043
 0.8600	 0.000818	 0.001031	 0.000000	 0.000000	 0.119222
 0.8800	 0.000837	 0.000904	 0.000000	 0.000000	 0.120401
 0.9000	 0.000854	 0.000774	 0.000000	 0.000000	 0.121579
 0.9200	 0.000868	 0.000642	 0.000000	 0.000000	 0.122758
 0.9400	 0.000879	 0.000507	 0.000000	 0.000000	 0.123937
 0.9600	 0.000888	 0.000362	 0.000000	 0.000000	 0.125116
 0.9800	 0.000894	 0.000209	 0.000000	 0.000000	 0.126295
 1.0000	 0.000896	 0.000048	 0.000000	 0.000000	 0.127473


 -------- Mode No.   6  (freq = 0.246167E+01 Hz)

span_loc	s-s disp	s-s slope	f-a disp	f-a slope	twist

 0.0000	 0.017830	-0.016981	 0.000000	 0.000000	 0.013310
 0.0200	 0.017387	-0.027204	 0.000000	 0.000000	 0.013478
 0.0400	 0.016742	-0.037166	 0.000000	 0.000000	 0.013646
 0.0600	 0.015901	-0.046878	 0.000000	 0.000000	 0.013814
 0.0800	 0.014868	-0.056320	 0.000000	 0.000000	 0.013982
 0.1000	 0.013650	-0.065463	 0.000000	 0.000000	 0.014150
 0.1200	 0.012251	-0.074282	 0.000000	 0.000000	 0.014319
 0.1400	 0.010680	-0.082752	 0.000000	 0.000000	 0.014487
 0.1600	 0.008943	-0.090841	 0.000000	 0.000000	 0.014655
 0.1800	 0.007048	-0.098524	 0.000000	 0.000000	 0.014823
 0.2000	 0.005004	-0.105772	 0.000000	 0.000000	 0.014991
 0.2200	 0.002820	-0.112559	 0.000000	 0.000000	 0.015159
 0.2400	 0.000505	-0.118853	 0.000000	 0.000000	 0.015327
 0.2600	-0.001931	-0.124619	 0.000000	 0.000000	 0.015495
 0.2800	-0.004477	-0.129827	 0.000000	 0.000000	 0.015663
 0.3000	-0.007121	-0.134441	 0.000000	 0.000000	 0.015831
 0.3200	-0.009851	-0.138429	 0.000000	 0.000000	 0.015999
 0.3400	-0.012654	-0.141759	 0.000000	 0.000000	 0.016167
 0.3600	-0.015517	-0.144406	 0.000000	 0.000000	 0.016335
 0.3800	-0.018426	-0.146325	 0.000000	 0.000000	 0.016504
 0.4000	-0.021365	-0.147468	 0.000000	 0.000000	 0.016672
 0.4200	-0.024319	-0.147787	 0.000000	 0.000000	 0.016840
 0.4400	-0.027271	-0.147230	 0.000000	 0.000000	 0.017008
 0.4600	-0.030202	-0.145746	 0.000000	 0.000000	 0.017176
 0.4800	-0.033094	-0.143277	 0.000000	 0.000000	 0.017344
 0.5000	-0.035926	-0.139779	 0.000000	 0.000000	 0.017512
 0.5200	-0.038677	-0.135203	 0.000000	 0.000000	 0.017680
 0.5400	-0.041326	-0.129500	 0.000000	 0.000000	 0.017848
 0.5600	-0.043849	-0.122643	 0.000000	 0.000000	 0.018016
 0.5800	-0.046223	-0.114581	 0.000000	 0.000000	 0.018184
 0.6000	-0.048423	-0.105272	 0.000000	 0.000000	 0.018352
 0.6200	-0.050424	-0.094666	 0.000000	 0.000000	 0.018520
 0.6400	-0.052199	-0.082708	 0.000000	 0.000000	 0.018688
 0.6600	-0.053722	-0.069357	 0.000000	 0.000000	 0.018856
 0.6800	-0.054962	-0.054548	 0.000000	 0.000000	 0.019025
 0.7000	-0.055892	-0.038238	 0.000000	 0.000000	 0.019193
 0.7200	-0.056479	-0.020363	 0.000000	 0.000000	 0.019361
 0.7400	-0.056693	-0.000859	 0.000000	 0.000000	 0.019529
 0.7600	-0.056500	 0.020322	 0.000000	 0.000000	 0.019697
 0.7800	-0.055866	 0.043263	 0.000000	 0.000000	 0.019865
 0.8000	-0.054764	 0.067085	 0.000000	 0.000000	 0.020033
 0.8200	-0.053180	 0.091429	 0.000000	 0.000000	 0.020201
 0.8400	-0.051107	 0.116090	 0.000000	 0.000000	 0.020369
 0.8600	-0.048541	 0.140575	 0.000000	 0.000000	 0.020537
 0.8800	-0.045488	 0.164866	 0.000000	 0.000000	 0.020705
 0.9000	-0.041950	 0.189050	 0.000000	 0.000000	 0.020873
 0.9200	-0.037929	 0.213138	 0.000000	 0.000000	 0.021041
 0.9400	-0.033424	 0.237411	 0.000000	 0.000000	 0.021209
 0.9600	-0.028423	 0.262788	 0.000000	 0.000000	 0.021377
 0.9800	-0.022903	 0.289293	 0.000000	 0.000000	 0.021546
 1.0000	-0.016842	 0.316976	 0.000000	 0.000000	 0.021714

For convenience of comparison, I copy and attach the OC4 results from NREL/CP-5000-54124 and modes obtained by me here:

 Running BModes (v1.03.01, 25-Sept-2007, compiled using double precision).
 Linked with the NWTC Subroutine Library (v1.01.08, 26-Sep-2007).

  all parameters checked : o.k.

  ******** modal analysis results **********

  eigenvalue( 1) =0.368443D+11   mode  1 frequency =   0.319914  (1st side-side) 
  eigenvalue( 2) =0.374922D+11   mode  2 frequency =   0.322715  (1st fore-aft)
  eigenvalue( 3) =0.483012D+12   mode  3 frequency =   1.158318  (2st side-side)
  eigenvalue( 4) =0.514288D+12   mode  4 frequency =   1.195232  (2st fore-aft)
  eigenvalue( 5) =0.122006D+13   mode  5 frequency =   1.840942  (1st twist)
  eigenvalue( 6) =0.218153D+13   mode  6 frequency =   2.461666
  eigenvalue( 7) =0.319175D+13   mode  7 frequency =   2.977577
  eigenvalue( 8) =0.104610D+14   mode  8 frequency =   5.390582
  eigenvalue( 9) =0.123930D+14   mode  9 frequency =   5.867289
  eigenvalue(10) =0.162585D+14   mode 10 frequency =   6.720311
  eigenvalue(11) =0.180712D+14   mode 11 frequency =   7.085043
  eigenvalue(12) =0.564525D+14   mode 12 frequency =  12.522482
  eigenvalue(13) =0.576709D+14   mode 13 frequency =  12.656890
  eigenvalue(14) =0.166495D+15   mode 14 frequency =  21.505512
  eigenvalue(15) =0.168955D+15   mode 15 frequency =  21.663798
  eigenvalue(16) =0.253024D+15   mode 16 frequency =  26.511195
  eigenvalue(17) =0.523198D+15   mode 17 frequency =  38.122539
  eigenvalue(18) =0.526391D+15   mode 18 frequency =  38.238703
  eigenvalue(19) =0.135523D+16   mode 19 frequency =  61.355765
  eigenvalue(20) =0.135901D+16   mode 20 frequency =  61.441261

Do you think this results (including distinguished tower modes ) are reasonable and correct? Thank you!

Best Regards,

Dear @Baoxuan.Wang,

Yes, those results make more reasonable.

Best regards,