4.14.1. Input Files
The user configures each StC instance with a separate input file. This input file defines the location of the StC relative to its mounting location, and defines the properties. It can also be used with an external forces file to apply a timeseries load at the location (primarily used for diagnostic purposes).
4.14.1.1. Units
Structural Control uses the SI system (kg, m, s, N). Angles are assumed to be in radians unless otherwise specified.
4.14.1.2. Structural Control Locations
The Structural Control input file defines the location and properties of the StC instance. The location is relative to the type of StC given in the main ServoDyn input file (see Section 4.13.1.2.11). The four location types are Nacelle, Tower, Blade, and Platform.
The mapping information for the StC will be given in the main OpenFAST summary file.
4.14.1.2.1. Nacelle StC
This StC mounting location is attached relative to the nacelle reference point. It will track with all nacelle motions (including motions due to yaw, tower flex, and platform motions).
4.14.1.2.2. Tower StC
This StC mounting location is attached to the tower mesh at the height specified above the tower base. This StC attachment will move with the line mesh at that height. For example, an StC mounted at 85 m on a 90 m tower will move with the mesh line corresponding to the 85 m height position on the tower center line.
4.14.1.2.3. Blade StC
This StC mounting location is attached to the blade structural center at the specified distance from the blade root along the z-axis of the blade (IEC blade coordinate system). This location will follow all blade deformations and motions (including blade twist when used with BeamDyn). This option is available with both the BeamDyn and ElastoDyn blade representations.
When this option is used, identical StCs will be attached at each of the blades.
The response if each blade mounted StC is tracked separately and is available in
the output channels given in the ServoDyn tab of the
OutListParameters.xlsx.
4.14.1.2.4. Platform StC
This StC mounting location is located relative to the platform reference point. When a rigid body platform is modeled (such as a rigid semi-submersible), it is attached to the platform reference point. When a flexible floating body is modeled, the StC is attached to the SubDyn mesh.
4.14.1.3. Structural Control Input File
The input file may have an arbitrary number of commented header lines, and
commented lines at any location in the input file.
(Example Structural Control input file for tuned mass damper on
tower for NREL 5 MW TLP):
4.14.1.4. StC Degrees of Freedom
StC_DOF_MODE [switch]
DOF mode {0: No StC or TLCD DOF; 1: StC_X_DOF, StC_Y_DOF, and/or StC_Z_DOF (three independent StC DOFs); 2: StC_XY_DOF (Omni-Directional StC); 3: TLCD; 4: Prescribed force/moment time series; 5: Force determined by external DLL}
StC_X_DOF [flag]
DOF on or off for StC X [Used only when StC_DOF_MODE==1 ]
StC_Y_DOF [flag]
DOF on or off for StC Y [Used only when StC_DOF_MODE==1 ]
StC_Z_DOF [flag]
DOF on or off for StC Z [Used only when StC_DOF_MODE==1 ]
4.14.1.5. StC Location
The location of the StC is relative to the component it is attached to. This is specified in the main ServoDyn input file. See description above.
StC_P_X [m]
At rest X position of StC
StC_P_Y [m]
At rest Y position of StC
StC_P_Z [m]
At rest Z position of StC
4.14.1.6. StC Initial Conditions
used only when StC_DOF_MODE==1 or 2
StC_X_DSP [m]
StC X initial displacement [relative to at rest position]
StC_Y_DSP [m]
StC Y initial displacement [relative to at rest position]
StC_Z_DSP [m]
StC Z initial displacement [relative to at rest position; used only when StC_DOF_MODE==1 and StC_Z_DOF==TRUE ]
StC_Z_PreLd [N]
StC Z spring preload. Either a direct value for the spring preload in Newtons, or “gravity” for pre-loading spring to shift the at rest position of the StC Z mass when gravity is acting on it using \(F_{Z_{PreLoad}} = M_Z * G\), or “none” to disable spring pre-load. See Section 4.14.2.1.4.2 for details of implementation. [used only when StC_DOF_MODE=1 and StC_Z_DOF=TRUE ]
4.14.1.7. StC Configuration
used only when StC_DOF_MODE==1 or 2
StC_X_PSP [m]
Positive stop position – maximum X mass displacement
StC_X_NSP [m]
Negative stop position – minimum X mass displacement
StC_Y_PSP [m]
Positive stop position – maximum Y mass displacement
StC_Y_NSP [m]
Negative stop position – minimum Y mass displacement
StC_Z_PSP [m]
Positive stop position – maximum Z mass displacement [used only when StC_DOF_MODE==1 and StC_Z_DOF==TRUE ]
StC_Z_NSP [m]
Negative stop position – minimum Z mass displacement [used only when StC_DOF_MODE==1 and StC_Z_DOF==TRUE ]
4.14.1.8. StC Mass, Stiffness, & Damping
used only when StC_DOF_MODE==1 or 2
StC_X_M [kg]
StC X mass [used only when StC_DOF_MODE==1 and StC_X_DOF==TRUE ]
StC_Y_M [kg]
StC Y mass [used only when StC_DOF_MODE==1 and StC_Y_DOF==TRUE ]
StC_Z_M [kg]
StC Z mass [used only when StC_DOF_MODE==1 and StC_Z_DOF==TRUE ]
StC_XY_M [kg]
StC XY mass [used only when StC_DOF_MODE==2 ]
StC_X_K [N/m]
StC X stiffness
StC_Y_K [N/m]
StC Y stiffness
StC_Z_K [N/m]
StC Z stiffness [used only when StC_DOF_MODE==1 and StC_Z_DOF==TRUE ]
StC_X_C [N/(m/s)]
StC X damping
StC_Y_C [N/(m/s)]
StC Y damping
StC_Z_C [N/(m/s)]
StC Z damping [used only when StC_DOF_MODE==1 and StC_Z_DOF==TRUE ]
StC_X_KS [N/m]
Stop spring X stiffness
StC_Y_KS [N/m]
Stop spring Y stiffness
StC_Z_KS [N/m]
Stop spring Z stiffness [used only when StC_DOF_MODE==1 and StC_Z_DOF==TRUE]
StC_X_CS [N/(m/s)]
Stop spring X damping
StC_Y_CS [N/(m/s)]
Stop spring Y damping
StC_Z_CS [N/(m/s)]
Stop spring Z damping [used only when StC_DOF_MODE==1 and StC_Z_DOF==TRUE ]
4.14.1.9. StC User-Defined Spring Forces
used only when StC_DOF_MODE==1 or 2
Use_F_TBL [flag]
Use spring force from user-defined table
NKInpSt [-]
Number of spring force input stations
The table is expected to contain 6 columns for displacements and equvalent sprint forces: X, F_X, Y, F_Y, Z, and F_Z. Displacements are in meters (m) and forces in Newtons (N).
Example spring forces table:
X F_X Y F_Y Z F_Z
(m) (N) (m) (N) (m) (N)
-6.0000000E+00 -4.8000000E+06 -6.0000000E+00 -4.8000000E+06 -6.0000000E+00 -4.8000000E+06
-5.0000000E+00 -2.4000000E+06 -5.0000000E+00 -2.4000000E+06 -5.0000000E+00 -2.4000000E+06
-4.5000000E+00 -1.2000000E+06 -4.5000000E+00 -1.2000000E+06 -4.5000000E+00 -1.2000000E+06
-4.0000000E+00 -6.0000000E+05 -4.0000000E+00 -6.0000000E+05 -4.0000000E+00 -6.0000000E+05
-3.5000000E+00 -3.0000000E+05 -3.5000000E+00 -3.0000000E+05 -3.5000000E+00 -3.0000000E+05
-3.0000000E+00 -1.5000000E+05 -3.0000000E+00 -1.5000000E+05 -3.0000000E+00 -1.5000000E+05
-2.5000000E+00 -1.0000000E+05 -2.5000000E+00 -1.0000000E+05 -2.5000000E+00 -1.0000000E+05
-2.0000000E+00 -6.5000000E+04 -2.0000000E+00 -6.5000000E+04 -2.0000000E+00 -6.5000000E+04
0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00
2.0000000E+00 6.5000000E+04 2.0000000E+00 6.5000000E+04 2.0000000E+00 6.5000000E+04
2.5000000E+00 1.0000000E+05 2.5000000E+00 1.0000000E+05 2.5000000E+00 1.0000000E+05
3.0000000E+00 1.5000000E+05 3.0000000E+00 1.5000000E+05 3.0000000E+00 1.5000000E+05
3.5000000E+00 3.0000000E+05 3.5000000E+00 3.0000000E+05 3.5000000E+00 3.0000000E+05
4.0000000E+00 6.0000000E+05 4.0000000E+00 6.0000000E+05 4.0000000E+00 6.0000000E+05
4.5000000E+00 1.2000000E+06 4.5000000E+00 1.2000000E+06 4.5000000E+00 1.2000000E+06
5.0000000E+00 2.4000000E+06 5.0000000E+00 2.4000000E+06 5.0000000E+00 2.4000000E+06
6.0000000E+00 4.8000000E+06 6.0000000E+00 4.8000000E+06 6.0000000E+00 4.8000000E+06
4.14.1.10. StructCtrl Control
used only when StC_DOF_MODE==1 or 2
StC_CMODE [switch]
Control mode {0:none; 1: Semi-Active Control Mode; 2: Active Control Mode}. When using StC_DOF_MODE==5, StC_CMODE must be 2.
StC_SA_MODE [-]
Semi-Active control mode {1: velocity-based ground hook control; 2: Inverse velocity-based ground hook control; 3: displacement-based ground hook control 4: Phase difference Algorithm with Friction Force 5: Phase difference Algorithm with Damping Force}
StC_X_C_HIGH [-]
StC X high damping for ground hook control
StC_X_C_LOW [-]
StC X low damping for ground hook control
StC_Y_C_HIGH [-]
StC Y high damping for ground hook control
StC_Y_C_LOW [-]
StC Y low damping for ground hook control
StC_Z_C_HIGH [-]
StC Z high damping for ground hook control [used only when StC_DOF_MODE==1 and StC_Z_DOF==TRUE ]
StC_Z_C_LOW [-]
StC Z low damping for ground hook control [used only when StC_DOF_MODE==1 and StC_Z_DOF==TRUE ]
StC_X_C_BRAKE [-]
StC X high damping for braking the StC [currently unused. set to zero]
StC_Y_C_BRAKE [-]
StC Y high damping for braking the StC [currently unused. set to zero]
StC_Z_C_BRAKE [-]
StC Z high damping for braking the StC [used only when StC_DOF_MODE==1 and StC_Z_DOF==TRUE ] [currently unused. set to zero]
4.14.1.11. TLCD – Tuned Liquid Column Damper
used only when StC_DOF_MODE==3
L_X [m]
X TLCD total length
B_X [m]
X TLCD horizontal length
area_X [m^2]
X TLCD cross-sectional area of vertical column
area_ratio_X [-]
X TLCD cross-sectional area ratio [vertical column area divided by horizontal column area]
headLossCoeff_X [-]
X TLCD head loss coeff
rho_X [kg/m^3]
X TLCD liquid density
L_Y [m]
Y TLCD total length
B_Y [m]
Y TLCD horizontal length
area_Y [m^2]
Y TLCD cross-sectional area of vertical column
area_ratio_Y [-]
Y TLCD cross-sectional area ratio [vertical column area divided by horizontal column area]
headLossCoeff_Y [-]
Y TLCD head loss coeff
rho_Y [kg/m^3]
Y TLCD liquid density
4.14.1.12. Prescribed Time Series
A prescribed time series of forces and moments may be applied in place of the StC damper. The force and moment may be applied either in a global coordinate frame, or in a local (following) coordinate frame. This feature is used only when StC_DOF_MODE==4.
PrescribedForcesCoord [switch]
Prescribed forces are in global or local coordinates {1: global; 2: local}. When using StC_DOF_MODE==5, PrescribedForcesCoord must be 1.
PrescribedForcesFile [-]
Filename for the prescribed forces. The format expected is 7 columns: time, FX, FY, FZ, MX, MY, MZ. Values will be interpolated from the file between the given timestep and value sets. The input file may have an arbitrary number of commented header lines, and commented lines at any location in the input file.
Example prescribed time series file (example prescribed force
timeseries):
# This is an input file for the tower top force time-series in the TMD module of ServoDyn
#
# it has an arbitrary number of header lines denoted with #!% characters
! Another comment line
#
# Time, Fx, Fy, Fz, Mx, My, Mz
# (s) (N) (N) (N) (N-m) (N-m) (N-m)
0.0 0.0 0.0 0.0 0.0 0.0 0.0
4.0 1.0e5 0.0 0.0 0.0 0.0 0.0 # Start ramp -- this is a comment
40.0 1.0e5 0.0 0.0 0.0 0.0 0.0
# 40.0001 0.0 0.0 0.0 0.0 0.0 0.0 # This is a commented line
90. 0.0 0.0 0.0 0.0 0.0 0.0