Turbine Structural Model

A structural model may be loaded into a turbine definition by setting the model to CHRONO and loading the structural model main file through the open file dialog. When a structural model has been assigned to a turbine the structural model files may be examined by clicking View/Edit Struct. The dialog that shows the file contents can also be used to quickly change parameters of the structural model, without the need to modify and save the file outside of QBlade and then importing them again. This edit functionality however doesnt cause to reload files from the file system, such that changing the string of a blade parameter table doesnt lead to reloading the newly defined filename. Generally, it is recommended to only use this edit functionality to quickly change a few parameters, but to setup and work with the structural model files outside of QBlade in a text editor.

The structural model dialog.

Fig. 69 The structural model dialog.

An overview of the file structure of the structural model definition files is hown in Fig. 70. The main input file needs to be loaded through the dialog. It contains the main turbine parameters and the location of the structural data tables for the definition of the tower and the blades.

The file structure of the structural model input files.

Fig. 70 The file structure of the structural model input files.

Main Definition File

The structure of the main input file will be discussed. An exemplary file is shown below:

---------------------- QBLADE STRUCTURAL MODEL INPUT FILE -----------------
NREL 5MW Turbine
------------------------------- CHRONO PARAMETERS -------------------------
0.2             GLBGEOEPS - Global geometry epsilon for node placement

------------------------------- HAWT TURBINE CONFIGURATION ----------------
2.5             PRECONE - Rotor PreCone (deg) (HAWT only)
5               SHFTTILT - Turbine Shaft Tilt (deg) (HAWT only)
5.0191          OVERHANG - Rotor Overhang (m) (HAWT only)
1.96256         TWR2SHFT - Tower to Shaft distance (m) (HAWT only)

------------------------------- MASS AND INERTIA --------------------------
0.0             YAWBRMASS - Yaw Bearing Mass (kg) (HAWT only)
240000          NACMASS - Nacelle Mass (kg) (HAWT only)
1.9             NACCMX - Downwind distance from the tower-top to the nacelle CM (m) (HAWT only)
0.0             NACCMY - Lateral  distance from the tower-top to the nacelle CM (m) (HAWT only)
1.75            NACCMZ - Vertical distance from the tower-top to the nacelle CM (m) (HAWT only)
2607890         NACYINER - Nacelle Yaw Inertia (kg*m^2) (HAWT only)
56780           HUBMASS - Hub Mass (kg)
115926          HUBINER - Hub Inertia (kg*m^2)

------------------------------- DRIVETRAIN MODEL --------------------------
97              GBRATIO - gearbox ratio (N)
1.0             GBOXEFF - gearbox efficiency (0-1)
true            DRTRDOF - model drivetrain dynamics (true / false)
534.116         GENINER - Generator side (HSS) Inertia (kg*m^2)
867637000       DTTORSPR - Drivetrain torsional stiffness (N*m/rad)
6215000         DTTORDMP - Drivetrain torsional damping (N*m*s/rad)

------------------------------- BRAKE MODEL -------------------------------
0               BRKTORQUE - maximum brake torque
0               BRKDEPLOY - brake deploy time (s) (only used with DTU style controllers)
0               BRKDELAY - brake delay time (s) (only used with DTU style controllers)

------------------------------- SENSOR ERRORS -----------------------------
0               ERRORYAW - yaw error (deg) (HAWT only)
0               ERRORPITCH_1 - pitch error blade1 (deg)
0               ERRORPITCH_2 - pitch error blade2 (deg)
0               ERRORPITCH_3 - pitch error blade3 (deg)

------------------------------- BLADES ------------------------------------
3                               NUMBLD - Number of blades
NREL5MW_Blade.str               BLDFILE_1 - Name of file containing properties for blade 1
NREL5MW_Blade.str               BLDFILE_2 - Name of file containing properties for blade 2
NREL5MW_Blade.str               BLDFILE_3 - Name of file containing properties for blade 3

------------------------------- TOWER -------------------------------------
77.6                            TWRHEIGHT - Height of the tower (m)
OC3_Sparbuoy_Tower.str          TWRFILE - Name of file containing properties for the tower
OC3_Sparbuoy_Sub_LPMD.str       SUBFILE  - Name of the substructure file

------------------------------- DATA OUTPUT TYPES -------------------------
true                    FOR_OUT - store (local) forces at all chosen locations
true                    ROT_OUT - store (local) body rotations at all chosen locations
true                    MOM_OUT - store (local) moments at all chosen locations
true                    DEF_OUT - store (local) deflections at all chosen locations
true                    POS_OUT - store (global) positions at all chosen locations
true                    VEL_OUT - store (global) velocities at all chosen locations
true                    ACC_OUT - store (global) accelerations at all chosen locations
true                    LVE_OUT - store (local) velocities at all chosen locations
true                    LAC_OUT - store (local) accelerations at all chosen locations

------------------------------- DATA OUTPUT LOCATIONS ---------------------
any number, or zero, user defined positions can be chosen as output locations.
Locations can be assigned at any of the following components: blades, struts, tower
and guy cables. See the following examples for the used nomenclature:

BLD_1_1.0               - exemplary position, blade 1 at 100% normalized radius
BLD_1_0.8               - exemplary position, blade 1 at  80% normalized radius
BLD_1_0.5               - exemplary position, blade 1 at  50% normalized radius
BLD_1_0.4               - exemplary position, blade 1 at  40% normalized radius
BLD_1_0.2               - exemplary position, blade 1 at  20% normalized radius
BLD_1_0.0               - exemplary position, blade 1 at  00% normalized radius

BLD_2_1.0               - exemplary position, blade 2 at 100% normalized radius
BLD_2_0.8               - exemplary position, blade 2 at  80% normalized radius
BLD_2_0.5               - exemplary position, blade 2 at  50% normalized radius
BLD_2_0.4               - exemplary position, blade 2 at  40% normalized radius
BLD_2_0.2               - exemplary position, blade 2 at  20% normalized radius
BLD_2_0.0               - exemplary position, blade 2 at  00% normalized radius

BLD_3_1.0               - exemplary position, blade 3 at 100% normalized radius
BLD_3_0.8               - exemplary position, blade 3 at  80% normalized radius
BLD_3_0.5               - exemplary position, blade 3 at  50% normalized radius
BLD_3_0.4               - exemplary position, blade 3 at  40% normalized radius
BLD_3_0.2               - exemplary position, blade 3 at  20% normalized radius
BLD_3_0.0               - exemplary position, blade 3 at  00% normalized radius

TWR_1.00                - exemplary position, tower at 100% normalized height
TWR_0.90                - exemplary position, tower at  90% normalized height
TWR_0.80                - exemplary position, tower at  80% normalized height
TWR_0.70                - exemplary position, tower at  70% normalized height
TWR_0.60                - exemplary position, tower at  60% normalized height
TWR_0.50                - exemplary position, tower at  50% normalized height
TWR_0.40                - exemplary position, tower at  40% normalized height
TWR_0.30                - exemplary position, tower at  30% normalized height
TWR_0.20                - exemplary position, tower at  20% normalized height
TWR_0.10                - exemplary position, tower at  10% normalized height
TWR_0.00                - exemplary position, tower at   0% normalized height

The different sections of the structural model input file will now be briefly discussed.

------------------------------- HAWT TURBINE CONFIGURATION ----------------
2.5             PRECONE - Rotor PreCone (deg) (HAWT only)
5               SHFTTILT - Turbine Shaft Tilt (deg) (HAWT only)
5.0191          OVERHANG - Rotor Overhang (m) (HAWT only)
1.96256         TWR2SHFT - Tower to Shaft distance (m) (HAWT only)

In this section of the file the main geometrical turbine parameters are defined. These parameters are equivalent to the parameters discussed in Turbine Geometry.

------------------------------- MASS AND INERTIA --------------------------
0.0             YAWBRMASS - Yaw Bearing Mass (kg) (HAWT only)
240000          NACMASS - Nacelle Mass (kg) (HAWT only)
1.9             NACCMX - Downwind distance from the tower-top to the nacelle CM (m) (HAWT only)
0.0             NACCMY - Lateral  distance from the tower-top to the nacelle CM (m) (HAWT only)
1.75            NACCMZ - Vertical distance from the tower-top to the nacelle CM (m) (HAWT only)
2607890         NACYINER - Nacelle Yaw Inertia (kg*m^2) (HAWT only)
56780           HUBMASS - Hub Mass (kg)
115926          HUBINER - Hub Inertia (kg*m^2)

In this section of the input file mass and inertia properties are assigned to the nacelle and the hub. It should be noted here that the parameter HUBINER should only account for the rotational inertia of the hub itself, and not account for the inertia of the rotor blades as this is explicity included through the finite element model.

------------------------------- DRIVETRAIN MODEL --------------------------
97              GBRATIO - gearbox ratio (N)
1.0             GBOXEFF - gearbox efficiency (0-1)
true            DRTRDOF - model drivetrain dynamics (true / false)
534.116         GENINER - Generator side (HSS) Inertia (kg*m^2)
867637000       DTTORSPR - Drivetrain torsional stiffness (N*m/rad)
6215000         DTTORDMP - Drivetrain torsional damping (N*m*s/rad)

This section of the main input file defined the drive train model. The drive train model in QBlade is a simple 2 mass spring-damper model. An overview is given in Fig. 71. The drivetrain is parameterized by the main shaft torsional stiffness and damping, a high speed side (HSS) generator inertia and the low speed side (LSS) inertia. The LSS inertia (of shaft and Hub combined) should be summes up and assigned to the HUBINER value.

An overview of the drivetrain model in QBlade.

Fig. 71 An overview of the drivetrain model in QBlade.

------------------------------- BRAKE MODEL -------------------------------
0                       BRKTORQUE - maximum brake torque
0                       BRKDEPLOY - brake deploy time (s)
0                       BRKDELAY - brake delay time (s)

The brake in QBlade is defined as shown above. The brake is parameterized with a delay time, a deploy time and a maximum value for the brake torque. After the brake signal is emitted from the controller, or a brake event, after the delay time (BRKDELAY) has passed the brake is activated and ramped up to the maximum brake torque (BRKTORQUE) during the deploy time (BRKDEPLOY). An overview of this process is shown in Fig. 72.

An overview of the brake model in QBlade.

Fig. 72 An overview of the brake model in QBlade.

------------------------------- SENSOR ERRORS -----------------------------
0               ERRORYAW - yaw error (deg) (HAWT only)
0               ERRORPITCH_1 - pitch error blade1 (deg)
0               ERRORPITCH_2 - pitch error blade2 (deg)
0               ERRORPITCH_3 - pitch error blade3 (deg)

Sensor errors are defined for each blade pitch bearing sensor and the yaw bearing sensor. These errors are simply added to the corresponding signals as an offset.

------------------------------- BLADES ------------------------------------
3                               NUMBLD - Number of blades
NREL5MW_Blade.str               BLDFILE_1 - Name of file containing properties for blade 1
NREL5MW_Blade.str               BLDFILE_2 - Name of file containing properties for blade 2
NREL5MW_Blade.str               BLDFILE_3 - Name of file containing properties for blade 3

The location of the structural data tables for the blades is defined by the keywords shown above. The number of blades is defined by the parameter NUMBLD, this value overrides the number of blades that is defined in the turbine definition dialog. For each blade a keyword BLDFILE_X is searched for where the filename of the blade data table is defined. Different blade data tables can be assigned to each individual blade.

------------------------------- TOWER -------------------------------------
77.6                            TWRHEIGHT - Height of the tower (m)
OC3_Sparbuoy_Tower.str          TWRFILE - Name of file containing properties for the tower
OC3_Sparbuoy_Sub_LPMD.str       SUBFILE  - Name of the substructure file

The structural tower data table is defined in a similar fashion as for the blades. The keyword TWRHEIGHT defines the absolute height of the tower. The keyword SUBFILE points to a substructure file that can be used to define a more complicated floating or bottom fixed substructure for offshore wind turbines or to model soil dynamics. If the keyword SUBFILE is not defined then the tower will simply be rigidly contrained to the ground. More information on how a substructure file is defined is found in the section: Substructure Definition.

Loading Data and Sensor Locations

------------------------------- DATA OUTPUT TYPES -------------------------
true                    FOR_OUT - store (local) forces at all chosen locations
true                    ROT_OUT - store (local) body rotations at all chosen locations
true                    MOM_OUT - store (local) moments at all chosen locations
true                    DEF_OUT - store (local) deflections at all chosen locations
true                    POS_OUT - store (global) positions at all chosen locations
true                    VEL_OUT - store (global) velocities at all chosen locations
true                    ACC_OUT - store (global) accelerations at all chosen locations
true                    LVE_OUT - store (local) velocities at all chosen locations
true                    LAC_OUT - store (local) accelerations at all chosen locations

------------------------------- DATA OUTPUT LOCATIONS ---------------------
any number, or zero, user defined positions can be chosen as output locations.
Locations can be assigned at any of the following components: blades, struts, tower
and guy cables. See the following examples for the used nomenclature:

BLD_1_1.0               - exemplary position, blade 1 at 100% normalized radius
BLD_1_0.8               - exemplary position, blade 1 at  80% normalized radius
BLD_1_0.5               - exemplary position, blade 1 at  50% normalized radius
BLD_1_0.4               - exemplary position, blade 1 at  40% normalized radius
BLD_1_0.2               - exemplary position, blade 1 at  20% normalized radius
BLD_1_0.0               - exemplary position, blade 1 at  00% normalized radius

BLD_2_1.0               - exemplary position, blade 2 at 100% normalized radius
BLD_2_0.8               - exemplary position, blade 2 at  80% normalized radius
BLD_2_0.5               - exemplary position, blade 2 at  50% normalized radius
BLD_2_0.4               - exemplary position, blade 2 at  40% normalized radius
BLD_2_0.2               - exemplary position, blade 2 at  20% normalized radius
BLD_2_0.0               - exemplary position, blade 2 at  00% normalized radius

BLD_3_1.0               - exemplary position, blade 3 at 100% normalized radius
BLD_3_0.8               - exemplary position, blade 3 at  80% normalized radius
BLD_3_0.5               - exemplary position, blade 3 at  50% normalized radius
BLD_3_0.4               - exemplary position, blade 3 at  40% normalized radius
BLD_3_0.2               - exemplary position, blade 3 at  20% normalized radius
BLD_3_0.0               - exemplary position, blade 3 at  00% normalized radius

TWR_1.00                - exemplary position, tower at 100% normalized height
TWR_0.90                - exemplary position, tower at  90% normalized height
TWR_0.80                - exemplary position, tower at  80% normalized height
TWR_0.70                - exemplary position, tower at  70% normalized height
TWR_0.60                - exemplary position, tower at  60% normalized height
TWR_0.50                - exemplary position, tower at  50% normalized height
TWR_0.40                - exemplary position, tower at  40% normalized height
TWR_0.30                - exemplary position, tower at  30% normalized height
TWR_0.20                - exemplary position, tower at  20% normalized height
TWR_0.10                - exemplary position, tower at  10% normalized height
TWR_0.00                - exemplary position, tower at   0% normalized height

The last part of the main structural input file deals with the definition of loading data and sensor locations. The locations at which the data will be stored are defined through the following keywords that can be placed anywhere in the structural model main input file:

  • BLD_X_Y: Stores data for blade X at the normalized curved length position Y

  • STR_X_Y_Z: Stores data for strut Y of blade X at the normalized curved length position Z

  • TWR_X: Stores data for the tower at the normalized curved length position X

  • TRQ_X: Stores data for the torque tube at the normalized curved length position X

  • CAB_X_Y: Stores data for guy cable X at the normalized curved length position Y

Furthermore data is automatically stored at each inter body connection of the model. Each inter body connection is identified by a combination of two body name tags and a z value that gives the height position at which the connection was created during the model definition. In the following two exemplary auto-generated variable names are shown and explained:

  • Y l Mom. TRQ - BLD_3 z=29.7m: The moment around the local Y axis at the connection between the torque tube and blade 3, which was defined at a height of 29.7m. This result is given in the local coordinates of the torque tube since the TRQ tag is the first tag in the variable name.

  • X l For. STR_2_2 - BLD_2 z=27.5m: This example defines the local reaction force at the connection between the top strut of blade 2 and blade 2, given for the local X axis of the strut.

Nine different data types can be specified to be stored (true) or not (false) at all locations that are specified or automatically generated. These are:

  • true / false FOR_OUT: Store the local forces for all locations

  • true / false MOM_OUT: Store the local moments for all locations

  • true / false DEF_OUT: Store the local deflections for all locations

  • true / false ROT_OUT: Store the local accumulated rotations at all chosen locations

  • true / false POS_OUT: Store the global positions for all locations

  • true / false VEL_OUT: Store the global velocities for all locations

  • true / false ACC_OUT: Store the global accelerations for all locations

  • true / false LVE_OUT: Store the local velocities for all locations

  • true / false LAC_OUT: Store the local accelerations for all locations

The forces and moments that obtained from a structural body are the internal shear forces and bending moments. However, the forces and moments given at an inter body connection can be interpreted as the reaction forces and moments acting on the constraint. For an overview of the coordinate systems / conventions in which the simulation results are stored see the section: Coordinate Systems.

Blade and Tower Structural Data Tables

The cross-sectional beam properties of the blade, tower and strut bodies have to be defined in the form of structural data tables. An exemplary data table is shown below:

Structural Data Table Generated with : QBlade QBlade EE v x.x.x 64bit-windows-release; on 09.01.2022; at 18:14:21

0.0024          RAYLEIGHDMP
1.00            STIFFTUNER
1.00            MASSTUNER

20              DISC

ADDMASS_0.50_0.00 - add a point mass at relative position 0.50 with 0.00kg mass

LENFRACT_[-]  MASSD_[kg/m]  EIx_[N.m^2]   EIy_[N.m^2]   EA_[N]        GJ_[N.m^2]    GA_[N]        STRPIT_[deg]  KSX_[-]       KSY_[-]       RGX_[-]       RGY_[-]       XCM_[-]       YCM_[-]       XCE_[-]       YCE_[-]       XCS_[-]       YCS_[-]
0.0000E+00    7.1502E+02    1.8116E+10    1.8116E+10    9.7300E+09    5.5600E+09    6.9500E+08    0.0000E+00    5.0000E-01    5.0000E-01    3.2931E-01    3.2936E-01    -4.7995E-05   0.0000E+00    0.0000E+00    0.0000E+00    0.0000E+00    0.0000E+00
3.2520E-03    7.1502E+02    1.8116E+10    1.8116E+10    9.7300E+09    5.5600E+09    6.9500E+08    0.0000E+00    5.0000E-01    5.0000E-01    3.2931E-01    3.2936E-01    -4.7995E-05   0.0000E+00    0.0000E+00    0.0000E+00    0.0000E+00    0.0000E+00
1.9512E-02    8.1446E+02    1.9418E+10    1.9558E+10    1.0790E+10    5.4300E+09    7.7070E+08    0.0000E+00    5.0000E-01    5.0000E-01    3.2685E-01    3.2307E-01    7.0102E-03    0.0000E+00    0.0000E+00    0.0000E+00    0.0000E+00    0.0000E+00
3.5772E-02    7.7991E+02    1.7458E+10    1.9502E+10    1.0067E+10    4.9900E+09    7.1910E+08    0.0000E+00    5.0000E-01    5.0000E-01    3.0601E-01    3.1861E-01    3.8932E-03    0.0000E+00    5.4989E-03    0.0000E+00    5.4989E-03    0.0000E+00
5.2033E-02    7.7937E+02    1.5288E+10    1.9782E+10    9.8672E+09    4.6700E+09    7.0480E+08    0.0000E+00    5.0000E-01    5.0000E-01    2.8228E-01    3.1667E-01    5.4728E-03    0.0000E+00    1.5995E-02    0.0000E+00    1.5995E-02    0.0000E+00
6.8293E-02    6.2399E+02    1.0783E+10    1.4854E+10    7.6076E+09    3.4700E+09    5.4340E+08    0.0000E+00    5.0000E-01    5.0000E-01    2.6375E-01    3.0599E-01    1.4164E-02    0.0000E+00    2.8457E-02    0.0000E+00    2.8457E-02    0.0000E+00
8.4553E-02    4.7421E+02    7.2296E+09    1.0220E+10    5.4908E+09    2.3200E+09    3.9220E+08    0.0000E+00    5.0000E-01    5.0000E-01    2.4658E-01    2.9224E-01    2.5352E-02    0.0000E+00    4.0201E-02    0.0000E+00    4.0201E-02    0.0000E+00
1.0081E-01    4.4659E+02    6.3098E+09    9.1448E+09    4.9714E+09    1.9100E+09    3.5510E+08    0.0000E+00    5.0000E-01    5.0000E-01    2.3129E-01    2.8160E-01    3.5071E-02    0.0000E+00    5.1288E-02    0.0000E+00    5.1288E-02    0.0000E+00
1.1707E-01    4.2193E+02    5.5286E+09    8.0626E+09    4.4940E+09    1.5700E+09    3.2100E+08    0.0000E+00    5.0000E-01    5.0000E-01    2.1690E-01    2.7057E-01    4.6278E-02    0.0000E+00    6.4150E-02    0.0000E+00    6.4150E-02    0.0000E+00
1.3333E-01    4.0237E+02    4.9798E+09    6.8838E+09    4.0348E+09    1.1600E+09    2.8820E+08    0.0000E+00    5.0000E-01    5.0000E-01    2.0504E-01    2.5549E-01    5.5352E-02    0.0000E+00    7.6335E-02    0.0000E+00    7.6335E-02    0.0000E+00
1.4959E-01    4.2090E+02    4.9364E+09    7.0098E+09    4.0376E+09    1.0000E+09    2.8840E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.9141E-01    2.4658E-01    6.7216E-02    0.0000E+00    8.7894E-02    0.0000E+00    8.7894E-02    0.0000E+00
1.6585E-01    4.4898E+02    4.6914E+09    7.1680E+09    4.1692E+09    8.5600E+08    2.9780E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.7635E-01    2.4202E-01    6.8242E-02    0.0000E+00    1.0107E-01    0.0000E+00    1.0107E-01    0.0000E+00
1.8211E-01    4.3897E+02    3.9494E+09    7.2716E+09    4.0824E+09    6.7200E+08    2.9160E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.6368E-01    2.4883E-01    6.6958E-02    0.0000E+00    1.1356E-01    0.0000E+00    1.1356E-01    0.0000E+00
1.9837E-01    4.2777E+02    3.3866E+09    7.0812E+09    4.0866E+09    5.4700E+08    2.9190E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.5436E-01    2.5762E-01    5.8711E-02    0.0000E+00    1.2168E-01    0.0000E+00    1.2168E-01    0.0000E+00
2.1463E-01    4.0169E+02    2.9344E+09    6.2440E+09    3.6680E+09    4.4900E+08    2.6200E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.4756E-01    2.5220E-01    5.9779E-02    0.0000E+00    1.2323E-01    0.0000E+00    1.2323E-01    0.0000E+00
2.3089E-01    3.7157E+02    2.5690E+09    5.0484E+09    3.1472E+09    3.3600E+08    2.2480E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.4153E-01    2.4160E-01    6.8041E-02    0.0000E+00    1.2262E-01    0.0000E+00    1.2262E-01    0.0000E+00
2.4715E-01    3.6805E+02    2.3884E+09    4.9490E+09    3.0114E+09    3.1100E+08    2.1510E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.3776E-01    2.4075E-01    6.9442E-02    0.0000E+00    1.2360E-01    0.0000E+00    1.2360E-01    0.0000E+00
2.6341E-01    3.6496E+02    2.2722E+09    4.8076E+09    2.8826E+09    2.9200E+08    2.0590E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.3583E-01    2.3952E-01    7.0957E-02    0.0000E+00    1.2269E-01    0.0000E+00    1.2269E-01    0.0000E+00
2.9593E-01    3.5737E+02    2.0496E+09    4.5010E+09    2.6138E+09    2.6100E+08    1.8670E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.3211E-01    2.3616E-01    7.3227E-02    0.0000E+00    1.2305E-01    0.0000E+00    1.2305E-01    0.0000E+00
3.2846E-01    3.4754E+02    1.8284E+09    4.2434E+09    2.3576E+09    2.2900E+08    1.6840E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.2843E-01    2.3363E-01    7.8424E-02    0.0000E+00    1.2360E-01    0.0000E+00    1.2360E-01    0.0000E+00
3.6098E-01    3.3910E+02    1.5890E+09    3.9956E+09    2.1462E+09    2.0100E+08    1.5330E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.2363E-01    2.3296E-01    7.8316E-02    0.0000E+00    1.2421E-01    0.0000E+00    1.2421E-01    0.0000E+00
3.9350E-01    3.3050E+02    1.3619E+09    3.7506E+09    1.9446E+09    1.7400E+08    1.3890E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.1868E-01    2.3275E-01    7.8557E-02    0.0000E+00    1.2284E-01    0.0000E+00    1.2284E-01    0.0000E+00
4.2602E-01    3.1040E+02    1.1024E+09    3.4468E+09    1.6324E+09    1.4400E+08    1.1660E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.1139E-01    2.2858E-01    8.7855E-02    0.0000E+00    1.2396E-01    0.0000E+00    1.2396E-01    0.0000E+00
4.5854E-01    3.0238E+02    8.7584E+08    3.1388E+09    1.4322E+09    1.2000E+08    1.0230E+08    0.0000E+00    5.0000E-01    5.0000E-01    1.0343E-01    2.2650E-01    8.5572E-02    0.0000E+00    1.2279E-01    0.0000E+00    1.2279E-01    0.0000E+00
4.9106E-01    2.7734E+02    6.8124E+08    2.7342E+09    1.1687E+09    8.1200E+07    8.3480E+07    0.0000E+00    5.0000E-01    5.0000E-01    9.6993E-02    2.2246E-01    8.9951E-02    0.0000E+00    1.2425E-01    0.0000E+00    1.2425E-01    0.0000E+00
5.2358E-01    2.6666E+02    5.3466E+08    2.5550E+09    1.0475E+09    6.9100E+07    7.4820E+07    0.0000E+00    5.0000E-01    5.0000E-01    9.0303E-02    2.2464E-01    8.8604E-02    0.0000E+00    1.2292E-01    0.0000E+00    1.2292E-01    0.0000E+00
5.5610E-01    2.5451E+02    4.0894E+08    2.3338E+09    9.2302E+08    5.7500E+07    6.5930E+07    0.0000E+00    5.0000E-01    5.0000E-01    8.3338E-02    2.2561E-01    8.5360E-02    0.0000E+00    1.2426E-01    0.0000E+00    1.2426E-01    0.0000E+00
5.8862E-01    2.3236E+02    3.1458E+08    1.8284E+09    7.6076E+08    4.5900E+07    5.4340E+07    0.0000E+00    5.0000E-01    5.0000E-01    7.9830E-02    2.2268E-01    8.4224E-02    0.0000E+00    1.2569E-01    0.0000E+00    1.2569E-01    0.0000E+00
6.2114E-01    2.1094E+02    2.3870E+08    1.5848E+09    6.4806E+08    3.6000E+07    4.6290E+07    0.0000E+00    5.0000E-01    5.0000E-01    7.6068E-02    2.2493E-01    7.9155E-02    0.0000E+00    1.2420E-01    0.0000E+00    1.2420E-01    0.0000E+00
6.5366E-01    1.8894E+02    1.7584E+08    1.3234E+09    5.3970E+08    2.7400E+07    3.8550E+07    0.0000E+00    5.0000E-01    5.0000E-01    7.2179E-02    2.2638E-01    7.0245E-02    0.0000E+00    1.2575E-01    0.0000E+00    1.2575E-01    0.0000E+00
6.8618E-01    1.7387E+02    1.2601E+08    1.1837E+09    5.3116E+08    2.0900E+07    3.7940E+07    0.0000E+00    5.0000E-01    5.0000E-01    6.6939E-02    2.4642E-01    4.3584E-02    0.0000E+00    1.2414E-01    0.0000E+00    1.2414E-01    0.0000E+00
7.1870E-01    1.6262E+02    1.0725E+08    1.0202E+09    4.6004E+08    1.8500E+07    3.2860E+07    0.0000E+00    5.0000E-01    5.0000E-01    6.6508E-02    2.4696E-01    3.6522E-02    0.0000E+00    1.2581E-01    0.0000E+00    1.2581E-01    0.0000E+00
7.5122E-01    1.4632E+02    9.0874E+07    7.9786E+08    3.7576E+08    1.6300E+07    2.6840E+07    0.0000E+00    5.0000E-01    5.0000E-01    6.6749E-02    2.4513E-01    4.5051E-02    0.0000E+00    1.2407E-01    0.0000E+00    1.2407E-01    0.0000E+00
7.8374E-01    1.3644E+02    7.6314E+07    7.0966E+08    3.2886E+08    1.4500E+07    2.3490E+07    0.0000E+00    5.0000E-01    5.0000E-01    6.6198E-02    2.4839E-01    4.0603E-02    0.0000E+00    1.2588E-01    0.0000E+00    1.2588E-01    0.0000E+00
8.1626E-01    1.1296E+02    6.1054E+07    5.1814E+08    2.4402E+08    9.0700E+06    1.7430E+07    0.0000E+00    5.0000E-01    5.0000E-01    6.6835E-02    2.4572E-01    4.5184E-02    0.0000E+00    1.2398E-01    0.0000E+00    1.2398E-01    0.0000E+00
8.4878E-01    1.0403E+02    4.9476E+07    4.5486E+08    2.1154E+08    8.0600E+06    1.5110E+07    0.0000E+00    5.0000E-01    5.0000E-01    6.6071E-02    2.5059E-01    3.7078E-02    0.0000E+00    1.2596E-01    0.0000E+00    1.2596E-01    0.0000E+00
8.8130E-01    9.5044E+01    3.9354E+07    3.9508E+08    1.8158E+08    7.0800E+06    1.2970E+07    0.0000E+00    5.0000E-01    5.0000E-01    6.5143E-02    2.5583E-01    2.7860E-02    0.0000E+00    1.2388E-01    0.0000E+00    1.2388E-01    0.0000E+00
8.9756E-01    8.7412E+01    3.4664E+07    3.5378E+08    1.6030E+08    6.0900E+06    1.1450E+07    0.0000E+00    5.0000E-01    5.0000E-01    6.5499E-02    2.5874E-01    2.3511E-02    0.0000E+00    1.2342E-01    0.0000E+00    1.2342E-01    0.0000E+00
9.1382E-01    7.6781E+01    3.0408E+07    3.0478E+08    1.0923E+08    5.7500E+06    7.8020E+06    0.0000E+00    5.0000E-01    5.0000E-01    6.7897E-02    2.3439E-01    5.8270E-02    0.0000E+00    1.2811E-01    0.0000E+00    1.2811E-01    0.0000E+00
9.3008E-01    7.2427E+01    2.6516E+07    2.8140E+08    1.0009E+08    5.3300E+06    7.1490E+06    0.0000E+00    5.0000E-01    5.0000E-01    6.8201E-02    2.4056E-01    5.2444E-02    0.0000E+00    1.2366E-01    0.0000E+00    1.2366E-01    0.0000E+00
9.3821E-01    6.9786E+01    2.3842E+07    2.6166E+08    9.2246E+07    4.9400E+06    6.5890E+06    0.0000E+00    5.0000E-01    5.0000E-01    6.8860E-02    2.4603E-01    5.0497E-02    0.0000E+00    1.2917E-01    0.0000E+00    1.2917E-01    0.0000E+00
9.4634E-01    6.2494E+01    1.9628E+07    1.5876E+08    6.3224E+07    4.2400E+06    4.5160E+06    0.0000E+00    5.0000E-01    5.0000E-01    7.0184E-02    2.2737E-01    7.8974E-02    0.0000E+00    1.2693E-01    0.0000E+00    1.2693E-01    0.0000E+00
9.5447E-01    5.8886E+01    1.6002E+07    1.3789E+08    5.3326E+07    3.6600E+06    3.8090E+06    0.0000E+00    5.0000E-01    5.0000E-01    6.9485E-02    2.3028E-01    7.8893E-02    0.0000E+00    1.3004E-01    0.0000E+00    1.3004E-01    0.0000E+00
9.6260E-01    5.5273E+01    1.2830E+07    1.1879E+08    4.4534E+07    3.1300E+06    3.1810E+06    0.0000E+00    5.0000E-01    5.0000E-01    6.8804E-02    2.3374E-01    7.7403E-02    0.0000E+00    1.2753E-01    0.0000E+00    1.2753E-01    0.0000E+00
9.7073E-01    5.1724E+01    1.0080E+07    1.0163E+08    3.6904E+07    2.6400E+06    2.6360E+06    0.0000E+00    5.0000E-01    5.0000E-01    6.8277E-02    2.3815E-01    7.4901E-02    0.0000E+00    1.2462E-01    0.0000E+00    1.2462E-01    0.0000E+00
9.7886E-01    4.8253E+01    7.5502E+06    8.5064E+07    2.9918E+07    2.1700E+06    2.1370E+06    0.0000E+00    5.0000E-01    5.0000E-01    6.6807E-02    2.4331E-01    7.4254E-02    0.0000E+00    1.2173E-01    0.0000E+00    1.2173E-01    0.0000E+00
9.8699E-01    4.3884E+01    4.6004E+06    6.4260E+07    2.1308E+07    1.5800E+06    1.5220E+06    0.0000E+00    5.0000E-01    5.0000E-01    6.1430E-02    2.4597E-01    8.1096E-02    0.0000E+00    1.2205E-01    0.0000E+00    1.2205E-01    0.0000E+00
9.9512E-01    1.2062E+01    2.5004E+05    6.6094E+06    4.8496E+06    2.5000E+05    3.4640E+05    0.0000E+00    5.0000E-01    5.0000E-01    5.4262E-02    2.6302E-01    7.4337E-02    0.0000E+00    1.2247E-01    0.0000E+00    1.2247E-01    0.0000E+00
1.0000E+00    1.0867E+01    1.6996E+05    5.0106E+06    3.5294E+06    1.9000E+05    2.5210E+05    0.0000E+00    5.0000E-01    5.0000E-01    4.4641E-02    2.6025E-01    7.1103E-02    0.0000E+00    1.2487E-01    0.0000E+00    1.2487E-01    0.0000E+00


RGBCOLOR
R       G       B
220     220     220

The keyword RAYLEIGHDMP defines a stiffness proportional Rayleigh damping coefficient. The parameters STIFFTUNER and MASSTUNER can be used to tune the global stiffness or mass properties of the data table through a multiplication by this factor. The keyword RGBCOLOR defines the rgb values that are used to color the structural body during the 3D visualization. The keyword DISC controls the discretization of the body into structural nodes. The following options are available:

  • 20 DISC: Discretization into 20 equally spaced (along the curved length) structural nodes.

  • struct DISC: The discretization is carried out after the discretization in the structural data table.

  • aero DISC: The discretization is carried out after the discretization in the aerodynamic blade data table (only for blade bodies).

The following table gives an overview of the entries of the structural data table:

Col. Nr.

Name

Explanation

Unit

1

Length

Curved length distance from the first body node normalized by the body length

2

Mass density

Mass per unit length

kg/m

3

Bend. stiff. X

Bending Stiffness around X (\(EI_{xx}\))

Nm^2

4

Bend. stiff. Y

Bending Stiffness around Y (\(EI_{yy}\))

Nm^2

5

Axial stiff.

Longitudinal Stiffness (\(EA\))

N

6

Tors. stiff.

Torsional Stiffness (\(GJ\))

Nm^2

7

Shear stiff.

Shear Stiffness (\(GA\)) (not used with Euler beams)

N

8

Str. pitch

Structural pitch angle between reference X axis and elastic X axis

deg

9

Shear factor X

Shear factor for force in principal bending axis X

10

Shear factor Y

Shear factor for force in principal bending axis Y

11

Radius of gyration X

Norm. radius of inertia corresponding to a rotation around the elastic axis X

%chord

12

Radius of gyration Y

Norm. radius of inertia corresponding to a rotation around the elastic axis Y

%chord

13

Center of mass X

Norm. center of mass position X

%chord

14

Center of mass Y

Norm. center of mass position Y

%chord

15

Center of elast. X

Norm. center of elasticity position X

%chord

16

Center of elast. Y

Norm. center of elasticity position Y

%chord

17

Center of shear X

Norm. center of shear position X

%chord

18

Center of shear Y

Norm. center of shear position Y

%chord

19

Diameter

Cross section diameter

m

20

Drag

Drag coefficient for aerodynamic drag

The local cross-sectional coordinate system for the definition of the structural data table is shown in Fig. 73.

Visualization of the local coordinate system that is used to define the cross sectional beam properties.

Fig. 73 Visualization of the local coordinate system that is used to define the cross sectional beam properties.

Substructure Definition

As with the other structural definition files, the substructure is defined by a series of keywords that are recognized by QBlade when creating the turbine. The format is the same as with the other structural file definitions:

  • <Value> <Keyword>, for parameters defined by a single values.

  • <Keyword> <new line> <Header> <new line> <Values> for parameters defined by a table. The <Header> <new line> part is only optional and can be omitted.

A table is identified by its Keyword and the row and column count of the subsequent ASCII values, which need to separated by space(s) or tab(s). An example of a table with two rows and tree columns is shown below.

<Keyword>

<Header 1>

<Header 2>

<Header 3>

<Value 1,1>

<Value 1,2>

<Value 1,3>

<Value 2,1>

<Value 2,2>

<Value 2,3>

There is no particular oder in which these keywords should be placed. The only exception is when defining tables. When a table is defined by a keyword, it should be immediately followed by the table header (optional) and the table content.

Main keywords used to define the substructure.

Fig. 74 Main keywords used to define the substructure. Each keyword is defined in detail in the text.

The main keywords that are used to define a substructure are shown in Fig. 74. This figure also shows the relationship between each of the keywords. It should also be noted that QBlade allows the user to combine elements from the Linear Potential Flow Theory and Morison Equation hydrodynamic models freely. So the user should be careful when setting up the substructure in QBlade so that the model remains consistent.

Following keywords can be used to define the substructure.

General Substructure Parameters

  • ISFLOATING is a flag that determines if the substructure is floating of bottom-fixed. If the structure is bottom-fixed the joint coordinates (see SUBJOINTS below) are assigned in a coordinate system with its origin placed at the seabed. For floaters, the origin is placed at the mean see level (MSL) and marks the floaters’s neutral point (NP)

  • WATERDEPTH sets the design water depth of the substructure, this value is only used for visualization of the turbine and the identification of flooded members. Note that this water depth is only for the turbine setup and is not used for offshore calculations.

  • WATERDENSITY: sets the water density to calculate the mass of the flooded members. Note that this water density is only for the turbine setup and is not used for offshore calculations.

  • STIFFTUNER is a multiplication factor that affects the stiffness of the flexible elements defined in SUBELEMENTS.

  • MASSTUNER is a multiplication factor that affects the mass density of ALL elements defined in SUBELEMENTS.

  • BUOYANCYTUNER is a multiplication factor that affects the calculation of the explicit buoyancy forces. Buoyancy caused by the linear hydrodynamic stiffness matrix is not affected by this factor.

  • ADVANCEDBUOYANCY is an option to use an advanced discretization technique to calculate the explicit buoyancy of partially submerged members, especially useful if non-vertical substructure members are located close to the mean sea level. The value used must be a square integer number (a value of 100 is suggested).

  • STATICBUOYANCY is an optional flag that controls the way the buoyancy arising from the linear hydrodynamic stiffness matrix is calculated in QBlade. If set to true, the buoyancy (vertical hydrodynamic stiffness along the global z-axis) is considering only the mean sea level. If set to false (default), the local wave elevation, at the REF_HYDRO_POS, is used to calculate the buoyancy.

  • TRANSITIONBLOCK adds a rectangle between the substructure and the tower base. It is used just for visualization purposes.

    Width

    Length

    Height

    <Value 1>

    <Value 2>

    <Value 3>

  • TRANSITIONCYLINDER adds a cylinder between the substructure and the tower base. It is used just for visualization purposes.

    Height

    Diameter

    <Value 1>

    <Value 2>

  • RGBCOLOR defines the color of the complete substructure. It is used just for visualization purposes.

    Red

    Green

    Blue

    <Value 1>

    <Value 2>

    <Value 3>

Substructure Geometry and Elements

  • SUBJOINTS is a table that is used to place spatial points that help define the members of the substructure. Each row of the table defines one joint and has four entries: the first gives the id number of the joint and the other three the cartesian coordinates of the joint (in m). The origin is the seabed if ISFLOATING is false and the MSL if ISFLOATING is true. The table is structured as follows:

    JointID

    JointX

    JointY

    JointZ

    1

    <Value 1>

    <Value 2>

    <Value 3>

  • JOINTOFFSET is a table that can be used to apply a global offset to the positions of ALL SUBJOINTS. Note that the offset is only applied to the joints and not the mass and hydro reference points defined in Linear Potential Flow-Related Parameters. The table is structured as follows:

    XOffset

    YOffset

    ZOffset

    <Value 1>

    <Value 2>

    <Value 3>

  • SUBELEMENTS is a table that defines the flexible elements that will be used for the substructure definition. Each row represents one (cylindrical) element, which is defined by its structural parameters. When setting up the substructure, one SUBELEMENT definition can be used for several SUBMEMBERS (see below). Each row has 20 entries. These define the structural parameters of the element. The entry placement is very similar to the blade and tower structural element table (see Blade and Tower Structural Data Tables). There two important differences though.

    1. The first entry is used to indicate the ID number of the element (ElemID).

    2. The last (20th) entry is used to indicate the Rayleigh damping of the element.

  • SUBELEMENTSRIGID is a table that defines rigid elements that will be used for the substructure definition. Each row represents one (cylindrical) element, which is defined by two attributes: its mass density and its diameter. When setting up the substructure, one SUBELEMENTRIGID definition can be used for several SUBMEMBERS (see below). An exemplary table is shown below.

    ElemID

    MassDens

    Diameter

    1

    <Value 1>

    <Value 2>

  • SUBMEMBERS is a table that contains the members that make up the turbine substructure. A member is defined between two entries of the SUBJOINTS table (defined by their ID nr.) and one entry from either the SUBELEMENT or SUBELEMENTRIGID tables. Additionally, it can have one Morison force coefficients group defined via the HYDROMEMBERCOEFF keyword and a marine growth entry from the MARINEGROWTH table. Also, this table allows the member to be flooded via a flooded cross sectional area entry (in m^2). The member can be subdivided into smaller elements for a more accurate structural and hydrodynamic evaluation. This is done in the ‘MembDisc’ column; it gives the maximum allowed length of a discrete subelement of the member (in m). Also, this table has the option to enable the buoyancy forces for the individual members (0 = False, 1 = True). Finally, the member can be optionally named for easier recognition in the output tables. The keyword table has the following format:

    MemID

    Joint1ID

    Joint2ID

    ElemID

    RigElmID

    HyCoID

    IsBuoy

    MarGroID

    FloodArea

    MembDisc

    Name

    1

    <Value 1>

    <Value 2>

    <Value 3>

    <Value 4>

    <Value 5>

    <Value 6>

    <Value 7>

    <Value 8>

    <Value 9>

    <Value 10>

  • SUBCONSTRAINTS is a table that defines the constraints of joints that are not connected by members, constraints of joints to the ground or to one TP_INTERFACE_POS transition piece point. Each row of the table has 12 entries. The first entry defines the constraint ID number. The next two entries define the two joints which can be constrained. The forth entry defines the number of the transition piece point (TP_INTERFACE_POS) that is to be constrained (see TP_INTERFACE_POS keyword and Linear Potential Flow-Related Parameters). Note that at least one joint of the substructure should be constrained to the transition piece (defined by TP_INTERFACE_POS) and that a constraint is defined either between two joints or one joint and one transition piece point. The fifth and sixth entries specify the connection method for bottom-fixed substructures to the ground (see Cable Elements, Ground-Fixing and Station-Keeping Parameters). The fifth entry specifies a stiff constraint with the ground. The sixth entry specifies a constraint to the ground via a non-linear spring-damping element (defined via an ID number). The last 6 entries specify which degrees of freedom are constrained: three translational and three rotational degrees of freedom. For these entries 0 means unconstrained and 1 means constrained.

    ConID

    Joint1ID

    Joint2ID

    TrPID

    Fixed

    SpringID

    DoF_tX

    DoF_tY

    DoF_tZ

    DoF_rX

    DoF_rY

    DoF_rZ

    1

    <Value 1>

    <Value 2>

    <Value 3>

    <Value 4>

    <Value 5>

    <Value 6>

    <Value 7>

    <Value 8>

    <Value 9>

    <Value 10>

    <Value 11>

  • MARINEGROWTH is a table that allows the user to define different types of marine growth that is present in the members. In QBlade, marine growth is simulated as an additional thickness that affects the diameter of the cylindrical element. An entry is defined by its ID number, the thickness of the growth (added to the cylinder radius) and the density of the growth.

    MaGroID

    Thickness

    Density

    1

    <Value 1>

    <Value 2>

  • TP_INTERFACE_POS are the (x,y,z) coordinates (in m) of the position of a particular transition piece point in the substructure. It can for example be the point where the substructure is connected to the tower base. For floating substructures it is defined in (x,y,z) [m] from the MSL = (0,0,0). For bottom fixed substructures, it is defined from the seabed. Note that the inertia and hydrodynamic reference points (REF_COG_POS and REF_HYDRO_POS) are always constrained to this point (see Linear Potential Flow-Related Parameters). There can be several transition piece points. Further points are then defined by additional keywords where an underscore and a number is added to the keyword (e.g. TP_INTERFACE_POS_2). This allows the user to define additional inertia and hydrodynamic reference points (see Linear Potential Flow-Related Parameters). All transition piece points have to be constrained to a least one joint of the substructure via the SUBCONSTRAINTS table. The structure of the table is:

    X-pos

    Y-pos

    Z-pos

    <Value 1>

    <Value 2>

    <Value 3>

  • TP_ORIENTATION defines the orientation of the tower base or RNA coordinate system which is connected to the TP_INTERFACE_POS by defining its \(X_t\)- and \(Y_t\)-Axis in the global coordinate system. If TP_ORIENTATION is not specified the default values are \(X_t=(1,0,0)\) and \(Y_t=(0,1,0)\), so the tower base coordinate system is aligned with the global coordinate system. The \(Z_t\)-Axis is evaluated from the cross-product of \(X_t\) and \(Y_t\).

    XGlobal

    YGlobal

    ZGlobal

    \(X_{t1}\)

    \(X_{t2}\)

    \(X_{t3}\)

    \(Y_{t1}\)

    \(Y_{t2}\)

    \(Y_{t3}\)

Cable Elements, Ground-Fixing and Station-Keeping Parameters

The connection to the ground is handled differently for floating and fixed-bottom substructures. For floating substructures, the anchoring is done via the mooring lines defined with the MOORELEMENTS and MOORMEMBERS keywords. These keywords can also be used to define flexible cable elements of the substructure. For bottom-fixed substructures, the connection the ground is defined in the SUBCONSTRAINTS table. It can be either a rigid connection or a connection via a system of non-linear springs and dampers. These latter elements are defined with the keywords NLSPRINGDAMPERS and optionally SPRINGDAMPK.

  • MOORELEMENTS is a table that contains the structural parameters of the flexible cable elements of the substructure such as mooring lines. Each row defines one set of parameters and has 7 values. These are the mooring element ID number, the mass density (in kg/m^3), the cross sectional area used for structural calculations (in m^2), the second moment of area (in m^4), Young’s modulus if the cable element (in N/m^2), the Rayleigh damping and the effective diameter of the cable used for hydrodynamic calculations.

    MoorID

    Mass dens

    Area

    2nd Mom. Area

    Young’s Mod.

    Rayl. Damp.

    Diameter

    1

    <Value 1>

    <Value 2>

    <Value 3>

    <Value 4>

    <Value 5>

    <Value 6>

  • MOORMEMBERS is a table that contains the information of the cable members (such as the mooring lines). Each row defines one cable member and has 10 entries. The first entry is the ID number of the cable member. The next two entries are the connection points of the cable member. There are several ways of defining the connection points. These are:

    • With the keyword JNT_<ID>, where <ID> represents the ID of the joint. This way, the cable is connected directly to a existing joint.

    • With the keyword FLT_<XPos>_<YPos>_<ZPos>, where <XPos>_<YPos>_<ZPos> represent the global (x,y,z) coordinates of the connection point (in m). Here, QBlade creates a constraint between this point and the floater to attach the cable.

    • With the keyword GRD_<XPos>_<YPos>, where <XPos>_<YPos> represent the global (x,y) (in m) coordinates of an anchor point which is located at the z-position of the seabed.

    The fourth entry is the length of the cable (in m). The fifth entry is the ID number of the cable element defined in MOORELEMENTS. The sixth entry is the ID number of the hydrodynamic coefficient group defined in HYDROMEMBERCOEFF. The seventh entry specifies if the cable is buoyant (= 1) or not (= 0). The eighth entry specifies the ID number of the marine growth element used for this cable (see MARINEGROWTH). The ninth entry is the number of discretization nodes used to discretize the cable and the tenth entry is the name of the cable element.

    MMemID

    Conn1

    Conn2

    Length

    MoorID

    HyCoID

    IsBuoy

    MaGroID

    MembDisc

    Name

    1

    <Value 1>

    <Value 2>

    <Value 3>

    <Value 4>

    <Value 5>

    <Value 6>

    <Value 7>

    <Value 8>

    <Value 9>

  • NLSPRINGDAMPERS is a table that defines one or more non-linear spring-damper systems for connecting the substructure to the ground. Each row represents a spring-damper system and has 2N + 3 entries, where N is the number of points on the definition table of the non-linear spring/damper. The first entry represents the ID number of the system (used in the SUBCONSTRAINTS table). The second entry defines the type of system that is being modelled. There are two options: ‘spring’ and ‘damp’. This affects the way the coefficients in the following entries are interpreted.

    • If ‘spring’ is selected, then QBlade expects the definition table to consists of displacement (in m) and stiffness (in N/m) entries.

    • If ‘damp’ is selected, then QBlade expects the definition table to consist of velocity (in m/s) and damping (in N/(m/s)) entires.

    The third row represents the stiffness/damping at zero displacement/velocity. The following 2N entries represent the additional lookup table entries for the non-linear spring/damper system. The order is \(x_1/v_1\), \(K/D(x_1/v_1)\); \(x_2/v_2\), \(K/D(x_2/v_2)\) and so on.

    SpringID

    Type

    \(K/D(x/v = 0)\)

    \(x_1/v_1\)

    \(K/D(x_1/v_1)\)

    \(x_2/v_2\)

    \(K/D(x_2/v_2)\)

    1

    <Value 1>

    <Value 2>

    <Value 3>

    <Value 4>

    <Value 5>

    <Value 6>

  • SPRINGDAMPK is an optional proportionality constant to add a damping value to the spring elements. If this keyword is used, then all of the spring elements defined in NLSPRINGDAMPERS are treated as spring-damping systems. The additional damping coefficients are calculated using the following approach: \(D_i\) = SPRINGDAMPK \(\cdot K_i\). This keyword does not affect the ‘damp’ elements defined in NLSPRINGDAMPERS.

Setting the Output Sensors

The output for the substructure is also controlled by keywords. QBlade can generate output for the members defined in the SUBMEMBERS and in the MOORMEMBERS tables. The logic of defining an ouput is as follows:

  • SUB_<MemID>_<RelPos> is the keyword used for setting an output of the submember with the ID number = <MemID> and a relative postion = <RelPos>. The relative position goes from 0 (= the position of Joint1ID) to 1 (= the postion of Joint2ID).

  • MOO_<MMemID>_<RelPos> is the keyword used for setting an output of the cable member with the ID number = <MMemID> and a relative postion = <RelPos>. The relative position goes from 0 (= the position of Conn1) to 1 (= the postion of Conn2).