Hydro forces convergence error on OpenFAST 4.1.2

Hi.

I’m trying to run a simulation of the NREL 5MW Wind Turbine with a monopile foundation using OpenFAST 4.1.2 for my undergraduate thesis. My simulation is based on the glue-code examples available in the OpenFAST GitHub repository.

I understand that, for fixed-bottom simulations, only PtfmYIner is typically provided, whereas for floating platforms, mass, roll inertia (PtfmRIner) and pitch inertia (PtfmPIner), while the platform products of inertia (PtfmXYIner, PtfmYZIner, and PtfmXZIner) remain zero.

The problem is that when I run the simulation with PtfmRIner and PtfmPIner set to zero, the forces and moments reported in the HydroDyn outputs increase to extraordinarily large values, and the simulation eventually crashes after a few minutes.

The modules I’m using are: AeroDyn, ElastoDyn, HydroDyn, SeaState, ServoDyn and SubDyn.

Am I required to provide nonzero values for PtfmRIner and PtfmPIner? Why didn’t you give non nonzero values for this two Iners in glue codes?

Thank you for your time and assistance.

Best regards,

Matheus

Dear @Matheus.Abreu,

When you enable both PtfmYDOF and YawDOF in ElastoDyn, it is necessary to set PtfrmYIner nonzero as discussed in the following forum topic: Wind Veer Parameter - #52 by Andre.White. It is not necessary to set PtfmRIner and PtfmPIner nonzero because roll and pitch motion of the platform will not have zero inertia.

I’m not sure why your model is diverging. What did you change relative to the OpenFAST model available in the r-test?

Best regards,

Thank you for your response, Jonkman.

I compared my input files with those from the r-test 5MW_OC3Mnpl_DLL_WTurb_WavesIrr. I obtained the glue codes at the beginning of this year, but I know that OpenFAST is updated regularly. In fact, I used this software once before, a few years ago.

I made some modifications because the r-test I mentioned was not running properly in OpenFAST 4.1.2. However, I did not identify any significant differences that could be causing this error. Compared to the 5MW_OC3Mnpl_DLL_WTurb_WavesIrr r-test, almost 100% of the files remain unchanged.

If I am required to provide the platform R and P inertias, that will not be a major problem. However, as a student with limited experience, I would prefer to run my simulation in the same way as your validation tests in order to avoid potential issues with the results.

I attached one figure showing the error message . The error does not occur when HydroDyn is disabled.

Since the r-tests are not running properly in OpenFAST 4.1.2 on my end, are there any available and up-to-date monopile simulations that include ElastoDyn, AeroDyn, TurbSim, ServoDyn, HydroDyn, SeaState, and SubDyn (or SoilDyn) that I could use as a reference for my future brazilian analyses? I only need a single working example to achieve my project goals.

Thank you for your time and assistance.

Dear @Matheus.Abreu,

Again, you should not need to set nonzero values for PtfmRIner and PtfmPIner.

The messages you shared from OpenFAST imply that your OpenFAST model is numerically unstable, but it is hard to understand what would cause this without knowing what you changed relative to the model available in the r-test? Can you describe the changes you’ve made or share your updated input files?

Best regards,

Here they go:

1ST - MAIN INPUT FILE

------- OpenFAST v4.1.2 INPUT FILE -----------------------------------------------
NREL 5.0 MW Baseline Wind Turbine with OC3 Monopile RF Configuration, for use in offshore analysis
---------------------- SIMULATION CONTROL --------------------------------------
False Echo - Echo input data to .ech (flag)
“FATAL” AbortLevel - Error level when simulation should abort (string) {“WARNING”, “SEVERE”, “FATAL”}
300 TMax - Total run time (s)
0.005 DT - Recommended module time step (s)
2 InterpOrder - Interpolation order for input/output time history (-) {1=linear, 2=quadratic}
0 NumCrctn - Number of correction iterations (-) {0=explicit calculation, i.e., no corrections}
99999 DT_UJac - Time between calls to get Jacobians (s)
1E+06 UJacSclFact - Scaling factor used in Jacobians (-)
---------------------- FEATURE SWITCHES AND FLAGS ------------------------------
1 CompElast - Compute structural dynamics (switch) {1=ElastoDyn; 2=ElastoDyn + BeamDyn for blades}
1 CompInflow - Compute inflow wind velocities (switch) {0=still air; 1=InflowWind; 2=external from OpenFOAM}
2 CompAero - Compute aerodynamic loads (switch) {0=None; 1=AeroDyn v14; 2=AeroDyn v15}
1 CompServo - Compute control and electrical-drive dynamics (switch) {0=None; 1=ServoDyn}
1 CompSeaSt - Compute sea state information (switch) {0=None; 1=SeaState}
1 CompHydro - Compute hydrodynamic loads (switch) {0=None; 1=HydroDyn}
1 CompSub - Compute sub-structural dynamics (switch) {0=None; 1=SubDyn; 2=External Platform MCKF}
0 CompMooring - Compute mooring system (switch) {0=None; 1=MAP++; 2=FEAMooring; 3=MoorDyn; 4=OrcaFlex}
0 CompIce - Compute ice loads (switch) {0=None; 1=IceFloe; 2=IceDyn}
0 MHK - MHK turbine type (switch) {0=Not an MHK turbine; 1=Fixed MHK turbine; 2=Floating MHK turbine}
---------------------- ENVIRONMENTAL CONDITIONS --------------------------------
9.80665 Gravity - Gravitational acceleration (m/s^2)
1.225 AirDens - Air density (kg/m^3)
1027 WtrDens - Water density (kg/m^3)
1.464e-05 KinVisc - Kinematic viscosity of working fluid (m^2/s)
335 SpdSound - Speed of sound in working fluid (m/s)
103500 Patm - Atmospheric pressure ¶ [used only for an MHK turbine cavitation check]
1700 Pvap - Vapour pressure of working fluid ¶ [used only for an MHK turbine cavitation check]
20 WtrDpth - Water depth (m)
0 MSL2SWL - Offset between still-water level and mean sea level (m) [positive upward]
---------------------- INPUT FILES ---------------------------------------------
“ElastoDyn.dat” EDFile - Name of file containing ElastoDyn input parameters (quoted string)
“unused” BDBldFile(1) - Name of file containing BeamDyn input parameters for blade 1 (quoted string)
“unused” BDBldFile(2) - Name of file containing BeamDyn input parameters for blade 2 (quoted string)
“unused” BDBldFile(3) - Name of file containing BeamDyn input parameters for blade 3 (quoted string)
“../5MW_Baseline/NRELOffshrBsline5MW_InflowWind_Steady13mps.dat” InflowFile - Name of file containing inflow wind input parameters (quoted string)
“AeroDyn.dat” AeroFile - Name of file containing aerodynamic input parameters (quoted string)
“ServoDyn.dat” ServoFile - Name of file containing control and electrical-drive input parameters (quoted string)
“SeaSt.dat” SeaStFIle - Name of file containing sea-state input parameters (quoted string)
“HydroDyn.dat” HydroFile - Name of file containing hydrodynamic input parameters (quoted string)
“SubDyn.dat” SubFile - Name of file containing sub-structural input parameters (quoted string)
“unused” MooringFile - Name of file containing mooring system input parameters (quoted string)
“unused” IceFile - Name of file containing ice input parameters (quoted string)
---------------------- OUTPUT --------------------------------------------------
False SumPrint - Print summary data to “.sum” (flag)
1 SttsTime - Amount of time between screen status messages (s)
99999 ChkptTime - Amount of time between creating checkpoint files for potential restart (s)
0.05 DT_Out - Time step for tabular output (s) (or “default”)
0 TStart - Time to begin tabular output (s)
1 OutFileFmt - Format for tabular (time-marching) output file (switch) {1: text file [.out], 2: binary file [.outb], 3: both 1 and 2, 4: uncompressed binary [.outb, 5: both 1 and 4}
True TabDelim - Use tab delimiters in text tabular output file? (flag) {uses spaces if false}
“ES10.3E2” OutFmt - Format used for text tabular output, excluding the time channel. Resulting field should be 10 characters. (quoted string)
---------------------- LINEARIZATION -------------------------------------------
False Linearize - Linearization analysis (flag)
False CalcSteady - Calculate a steady-state periodic operating point before linearization? [unused if Linearize=False] (flag)
3 TrimCase - Controller parameter to be trimmed {1:yaw; 2:torque; 3:pitch} [used only if CalcSteady=True] (-)
0.001 TrimTol - Tolerance for the rotational speed convergence [used only if CalcSteady=True] (-)
0.01 TrimGain - Proportional gain for the rotational speed error (>0) [used only if CalcSteady=True] (rad/(rad/s) for yaw or pitch; Nm/(rad/s) for torque)
0 Twr_Kdmp - Damping factor for the tower [used only if CalcSteady=True] (N/(m/s))
0 Bld_Kdmp - Damping factor for the blades [used only if CalcSteady=True] (N/(m/s))
2 NLinTimes - Number of times to linearize (-) [>=1] [unused if Linearize=False]
1 LinInputs - Inputs included in linearization (switch) {0=none; 1=standard; 2=all module inputs (debug)} [unused if Linearize=False]
30, 60 LinTimes - List of times at which to linearize (s) [1 to NLinTimes] [unused if Linearize=False]
1 LinOutputs - Outputs included in linearization (switch) {0=none; 1=from OutList(s); 2=all module outputs (debug)} [unused if Linearize=False]
False LinOutJac - Include full Jacobians in linearization output (for debug) (flag) [unused if Linearize=False; used only if LinInputs=LinOutputs=2]
False LinOutMod - Write module-level linearization output files in addition to output for full system? (flag) [unused if Linearize=False]
---------------------- VISUALIZATION ------------------------------------------
0 WrVTK - VTK visualization data output: (switch) {0=none; 1=initialization data only; 2=animation}
3 VTK_type - Type of VTK visualization data: (switch) {1=surfaces; 2=basic meshes (lines/points); 3=all meshes (debug)} [unused if WrVTK=0]
false VTK_fields - Write mesh fields to VTK data files? (flag) {true/false} [unused if WrVTK=0]
15 VTK_fps - Frame rate for VTK output (frames per second){will use closest integer multiple of DT} [used only if WrVTK=2]

2ND - ELASTODYN

------- ELASTODYN for OpenFAST v4.1.2 INPUT FILE ----------------------------------------------
NREL 5.0 MW Baseline Wind Turbine for Use in Offshore Analysis. Properties from Dutch Offshore Wind Energy Converter (DOWEC) 6MW Pre-Design (10046_009.pdf) and REpower 5M 5MW (5m_uk.pdf);
---------------------- SIMULATION CONTROL --------------------------------------
False Echo - Echo input data to “.ech” (flag)
3 Method - Integration method: {1: RK4, 2: AB4, or 3: ABM4} (-)
“default” DT - Integration time step (s)
---------------------- DEGREES OF FREEDOM --------------------------------------
True FlapDOF1 - First flapwise blade mode DOF (flag)
True FlapDOF2 - Second flapwise blade mode DOF (flag)
True EdgeDOF - First edgewise blade mode DOF (flag)
False TeetDOF - Rotor-teeter DOF (flag) [unused for 3 blades]
True DrTrDOF - Drivetrain rotational-flexibility DOF (flag)
True GenDOF - Generator DOF (flag)
True YawDOF - Yaw DOF (flag)
True TwFADOF1 - First fore-aft tower bending-mode DOF (flag)
True TwFADOF2 - Second fore-aft tower bending-mode DOF (flag)
True TwSSDOF1 - First side-to-side tower bending-mode DOF (flag)
True TwSSDOF2 - Second side-to-side tower bending-mode DOF (flag)
True PtfmSgDOF - Platform horizontal surge translation DOF (flag)
True PtfmSwDOF - Platform horizontal sway translation DOF (flag)
True PtfmHvDOF - Platform vertical heave translation DOF (flag)
True PtfmRDOF - Platform roll tilt rotation DOF (flag)
True PtfmPDOF - Platform pitch tilt rotation DOF (flag)
True PtfmYDOF - Platform yaw rotation DOF (flag)
---------------------- INITIAL CONDITIONS --------------------------------------
0 OoPDefl - Initial out-of-plane blade-tip displacement (meters)
0 IPDefl - Initial in-plane blade-tip deflection (meters)
0 BlPitch(1) - Blade 1 initial pitch (degrees)
0 BlPitch(2) - Blade 2 initial pitch (degrees)
0 BlPitch(3) - Blade 3 initial pitch (degrees) [unused for 2 blades]
0 TeetDefl - Initial or fixed teeter angle (degrees) [unused for 3 blades]
0 Azimuth - Initial azimuth angle for blade 1 (degrees)
12.1 RotSpeed - Initial or fixed rotor speed (rpm)
0 NacYaw - Initial or fixed nacelle-yaw angle (degrees)
0 TTDspFA - Initial fore-aft tower-top displacement (meters)
0 TTDspSS - Initial side-to-side tower-top displacement (meters)
0 PtfmSurge - Initial or fixed horizontal surge translational displacement of platform (meters)
0 PtfmSway - Initial or fixed horizontal sway translational displacement of platform (meters)
-0.0009 PtfmHeave - Initial or fixed vertical heave translational displacement of platform (meters)
0 PtfmRoll - Initial or fixed roll tilt rotational displacement of platform (degrees)
0 PtfmPitch - Initial or fixed pitch tilt rotational displacement of platform (degrees)
0 PtfmYaw - Initial or fixed yaw rotational displacement of platform (degrees)
---------------------- TURBINE CONFIGURATION -----------------------------------
3 NumBl - Number of blades (-)
63 TipRad - The distance from the rotor apex to the blade tip (meters)
1.5 HubRad - The distance from the rotor apex to the blade root (meters)
-2.5 PreCone(1) - Blade 1 cone angle (degrees)
-2.5 PreCone(2) - Blade 2 cone angle (degrees)
-2.5 PreCone(3) - Blade 3 cone angle (degrees) [unused for 2 blades]
0 HubCM - Distance from rotor apex to hub mass [positive downwind] (meters)
0 UndSling - Undersling length [distance from teeter pin to the rotor apex] (meters) [unused for 3 blades]
0 Delta3 - Delta-3 angle for teetering rotors (degrees) [unused for 3 blades]
0 AzimB1Up - Azimuth value to use for I/O when blade 1 points up (degrees)
-5.0191 OverHang - Distance from yaw axis to rotor apex [3 blades] or teeter pin [2 blades] (meters)
1.912 ShftGagL - Distance from rotor apex [3 blades] or teeter pin [2 blades] to shaft strain gages [positive for upwind rotors] (meters)
-5 ShftTilt - Rotor shaft tilt angle (degrees)
1.9 NacCMxn - Downwind distance from the tower-top to the nacelle CM (meters)
0 NacCMyn - Lateral distance from the tower-top to the nacelle CM (meters)
1.75 NacCMzn - Vertical distance from the tower-top to the nacelle CM (meters)
-3.09528 NcIMUxn - Downwind distance from the tower-top to the nacelle IMU (meters)
0 NcIMUyn - Lateral distance from the tower-top to the nacelle IMU (meters)
2.23336 NcIMUzn - Vertical distance from the tower-top to the nacelle IMU (meters)
1.96256 Twr2Shft - Vertical distance from the tower-top to the rotor shaft (meters)
87.6 TowerHt - Height of tower above ground level [onshore] or MSL [offshore] (meters)
10 TowerBsHt - Height of tower base above ground level [onshore] or MSL [offshore] (meters)
0 PtfmCMxt - Downwind distance from the ground level [onshore] or MSL [offshore] to the platform CM (meters)
0 PtfmCMyt - Lateral distance from the ground level [onshore] or MSL [offshore] to the platform CM (meters)
10 PtfmCMzt - Vertical distance from the ground level [onshore] or MSL [offshore] to the platform CM (meters)
10 PtfmRefzt - Vertical distance from the ground level [onshore] or MSL [offshore] to the platform reference point (meters)
---------------------- MASS AND INERTIA ----------------------------------------
0 TipMass(1) - Tip-brake mass, blade 1 (kg)
0 TipMass(2) - Tip-brake mass, blade 2 (kg)
0 TipMass(3) - Tip-brake mass, blade 3 (kg) [unused for 2 blades]
56780 HubMass - Hub mass (kg)
115926 HubIner - Hub inertia about rotor axis [3 blades] or teeter axis [2 blades] (kg m^2)
534.116 GenIner - Generator inertia about HSS (kg m^2)
240000 NacMass - Nacelle mass (kg)
2.60789E+06 NacYIner - Nacelle inertia about yaw axis (kg m^2)
0 YawBrMass - Yaw bearing mass (kg)
0 PtfmMass - Platform mass (kg)
2.56193E+09 PtfmRIner - Platform inertia for roll tilt rotation about the platform CM (kg m^2)
2.56193E+09 PtfmPIner - Platform inertia for pitch tilt rotation about the platform CM (kg m^2)
4.24265E+09 PtfmYIner - Platform inertia for yaw rotation about the platform CM (kg m^2)
0 PtfmXYIner - Platform xy moment of inertia about the platform CM (=-int(xydm)) (kg m^2)
0 PtfmYZIner - Platform yz moment of inertia about the platform CM (=-int(yzdm)) (kg m^2)
0 PtfmXZIner - Platform xz moment of inertia about the platform CM (=-int(xzdm)) (kg m^2)
---------------------- BLADE ---------------------------------------------------
5 BldNodes - Number of blade nodes (per blade) used for analysis (-)
“../5MW_Baseline/ElastoDyn_Blade.dat” BldFile(1) - Name of file containing properties for blade 1 (quoted string)
“../5MW_Baseline/ElastoDyn_Blade.dat” BldFile(2) - Name of file containing properties for blade 2 (quoted string)
“../5MW_Baseline/ElastoDyn_Blade.dat” BldFile(3) - Name of file containing properties for blade 3 (quoted string) [unused for 2 blades]
---------------------- ROTOR-TEETER --------------------------------------------
0 TeetMod - Rotor-teeter spring/damper model {0: none, 1: standard, 2: user-defined from routine UserTeet} (switch) [unused for 3 blades]
0 TeetDmpP - Rotor-teeter damper position (degrees) [used only for 2 blades and when TeetMod=1]
0 TeetDmp - Rotor-teeter damping constant (N-m/(rad/s)) [used only for 2 blades and when TeetMod=1]
0 TeetSStP - Rotor-teeter soft-stop position (degrees) [used only for 2 blades and when TeetMod=1]
0 TeetHStP - Rotor-teeter hard-stop position (degrees) [used only for 2 blades and when TeetMod=1]
0 TeetSSSp - Rotor-teeter soft-stop linear-spring constant (N-m/rad) [used only for 2 blades and when TeetMod=1]
0 Teetnone - Rotor-teeter hard-stop linear-spring constant (N-m/rad) [used only for 2 blades and when TeetMod=1]
0 TeetHSSp -
---------------------- YAW-FRICTION ----------------------------------------------
0 YawFrctMod - Yaw-friction model {0: none, 1: friction independent of yaw-bearing force and bending moment, 2: friction with Coulomb terms depending on yaw-bearing force and bending moment, 3: user defined model} (switch)
300 M_CSmax - Maximum static Coulomb friction torque (N-m) [M_CSmax when YawFrctMod=1; |Fz|*M_CSmax when YawFrctMod=2 and Fz<0]
0 M_FCSmax - Maximum static Coulomb friction torque proportional to yaw bearing shear force (N-m) [sqrt(Fx^2+Fy^2)*M_FCSmax; only used when YawFrctMod=2]
0 M_MCSmax - Maximum static Coulomb friction torque proportional to yaw bearing bending moment (N-m) [sqrt(Mx^2+My^2)*M_MCSmax; only used when YawFrctMod=2]
40 M_CD - Dynamic Coulomb friction moment (N-m) [M_CD when YawFrctMod=1; |Fz|*M_CD when YawFrctMod=2 and Fz<0]
0 M_FCD - Dynamic Coulomb friction moment proportional to yaw bearing shear force (N-m) [sqrt(Fx^2+Fy^2)*M_FCD; only used when YawFrctMod=2]
0 M_MCD - Dynamic Coulomb friction moment proportional to yaw bearing bending moment (N-m) [sqrt(Mx^2+My^2)*M_MCD; only used when YawFrctMod=2]
0 sig_v - Linear viscous friction coefficient (N-m/(rad/s))
0 sig_v2 - Quadratic viscous friction coefficient (N-m/(rad/s)^2)
0 OmgCut - Yaw angular velocity cutoff below which viscous friction is linearized (rad/s) -
---------------------- DRIVETRAIN ----------------------------------------------
100 GBoxEff - Gearbox efficiency (%)
97 GBRatio - Gearbox ratio (-)
8.67637E+08 DTTorSpr - Drivetrain torsional spring (N-m/rad)
6.215E+06 DTTorDmp - Drivetrain torsional damper (N-m/(rad/s))
---------------------- FURLING -------------------------------------------------
False Furling - Read in additional model properties for furling turbine (flag) [must currently be FALSE)
“unused” FurlFile - Name of file containing furling properties (quoted string) [unused when Furling=False]
---------------------- TOWER ---------------------------------------------------
20 TwrNodes - Number of tower nodes used for analysis (-)
“../5MW_Baseline/ElastoDyn_Tower.dat” TwrFile - Name of file containing tower properties (quoted string)
---------------------- OUTPUT --------------------------------------------------
False SumPrint - Print summary data to “.sum” (flag)
1 OutFile - Switch to determine where output will be placed: {1: in module output file only; 2: in glue code output file only; 3: both} (currently unused)
True TabDelim - Use tab delimiters in text tabular output file? (flag) (currently unused)
“ES10.3E2” OutFmt - Format used for text tabular output (except time). Resulting field should be 10 characters. (quoted string) [not checked for validity!] (currently unused)
0 TStart - Time to begin tabular output (s) (currently unused)
1 DecFact - Decimation factor for tabular output {1: output every time step} (-) (currently unused)
0 NTwGages - Number of tower nodes that have strain gages for output [0 to 9] (-)
0 TwrGagNd - List of tower nodes that have strain gages [1 to TwrNodes] (-) [unused if NTwGages=0]
0 NBlGages - Number of blade nodes that have strain gages for output [0 to 9] (-)
5, BldGagNd - List of blade nodes that have strain gages [1 to BldNodes] (-) [unused if NBlGages=0]
OutList - The next line(s) contains a list of output parameters. See OutListParameters.xlsx for a listing of available output channels, (-)
“OoPDefl1” - Blade 1 out-of-plane and in-plane deflections and tip twist
“IPDefl1” - Blade 1 out-of-plane and in-plane deflections and tip twist
“BldPitch1” - Blade 1 pitch angle
“Azimuth” - Blade 1 azimuth angle
“RotSpeed” - Low-speed shaft and high-speed shaft speeds
“GenSpeed” - Low-speed shaft and high-speed shaft speeds
“TTDspFA” - Tower fore-aft and side-to-side displacements and top twist
“TTDspSS” - Tower fore-aft and side-to-side displacements and top twist
“RootMyc1” - In-plane bending, out-of-plane bending, and pitching moments at the root of blade 1
“RotThrust” - Rotor thrust at the main bearing
“RotTorq” - Rotor torque at the main bearing
“RotPwr” - Rotor power (this is equivalent to the low-speed shaft power)
“TwrBsFxt” - Fore-aft shear, side-to-side shear, and vertical forces at the base of the tower (mudline)
“TwrBsFyt” - Fore-aft shear, side-to-side shear, and vertical forces at the base of the tower (mudline)
“TwrBsFzt” - Fore-aft shear, side-to-side shear, and vertical forces at the base of the tower (mudline)
“TwrBsMxt” - Side-to-side bending, fore-aft bending, and yaw moments at the base of the tower (mudline)
“TwrBsMyt” - Side-to-side bending, fore-aft bending, and yaw moments at the base of the tower (mudline)
“TwrBsMzt” - Side-to-side bending, fore-aft bending, and yaw moments at the base of the tower (mudline)
END of input file (the word “END” must appear in the first 3 columns of this last OutList line)
---------------------- NODE OUTPUTS --------------------------------------------
0 BldNd_BladesOut - Blades to output
99 BldNd_BlOutNd - Blade nodes on each blade (currently unused)
OutListED - The next line(s) contains a list of output parameters. See OutListParameters.xlsx, ElastoDyn_Nodes tab for a listing of available output channels, (-)
END of input file (the word “END” must appear in the first 3 columns of this last OutList line)

3RD - HYDRODYN

------- HydroDyn Input File ---------------------------------------------
NREL 5.0 MW offshore baseline floating platform input properties for the OC3 Monopile.
False Echo - Echo the input file data (flag)
---------------------- FLOATING PLATFORM --------------------------------------- [unused with WaveMod=6]
0 PotMod - Potential-flow model {0: none=no potential flow, 1: frequency-to-time-domain transforms based on WAMIT output, 2: fluid-impulse theory (FIT)} (switch)
1 ExctnMod - Wave-excitation model {0: no wave-excitation calculation, 1: DFT, 2: state-space} (switch) [only used when PotMod=1; STATE-SPACE REQUIRES .ssexctn INPUT FILE]
0 ExctnDisp - Method of computing Wave Excitation {0: use undisplaced position, 1: use displaced position, 2: use low-pass filtered displaced position) [only used when PotMod=1 and ExctnMod>0 and SeaState’s WaveMod>0]} (switch)
10 ExctnCutOff - Cutoff (corner) frequency of the low-pass time-filtered displaced position (Hz) [>0.0] [used only when PotMod=1, ExctnMod>0, and ExctnDisp=2]) [only used when PotMod=1 and ExctnMod>0 and SeaState’s WaveMod>0]} (switch)
0 PtfmYMod - Model for large platform yaw offset {0: Static reference yaw offset based on PtfmRefY, 1: dynamic reference yaw offset based on low-pass filtering the PRP yaw motion with cutoff frequency PtfmYCutOff} (switch)
0 PtfmRefY - Constant (if PtfmYMod=0) or initial (if PtfmYMod=1) platform reference yaw offset (deg)
0.01 PtfmYCutOff - Cutoff frequency for the low-pass filtering of PRP yaw motion when PtfmYMod=1 [>0.0; unused when PtfmYMod=0] (Hz)
36 NExctnHdg - Number of evenly distributed platform yaw/heading angles over the range of [-180, 180) deg for which the wave excitation shall be computed [>=2; unused when PtfmYMod=0] (-)
0 RdtnMod - Radiation memory-effect model {0: no memory-effect calculation, 1: convolution, 2: state-space} (switch) [only used when PotMod=1; STATE-SPACE REQUIRES .ss INPUT FILE]
60 RdtnTMax - Analysis time for wave radiation kernel calculations (sec) [only used when PotMod=1 and RdtnMod>0; determines RdtnDOmega=Pi/RdtnTMax in the cosine transform; MAKE SURE THIS IS LONG ENOUGH FOR THE RADIATION IMPULSE RESPONSE FUNCTIONS TO DECAY TO NEAR-ZERO FOR THE GIVEN PLATFORM!]
0.0125 RdtnDT - Time step for wave radiation kernel calculations (sec) [only used when PotMod=1 and ExctnMod>0 or RdtnMod>0; DT<=RdtnDT<=0.1 recommended; determines RdtnOmegaMax=Pi/RdtnDT in the cosine transform]
1 NBody - Number of WAMIT bodies to be used (-) [>=1; only used when PotMod=1. If NBodyMod=1, the WAMIT data contains a vector of size 6
NBody x 1 and matrices of size 6NBody x 6NBody; if NBodyMod>1, there are NBody sets of WAMIT data each with a vector of size 6 x 1 and matrices of size 6 x 6]
1 NBodyMod - Body coupling model {1: include coupling terms between each body and NBody in HydroDyn equals NBODY in WAMIT, 2: neglect coupling terms between each body and NBODY=1 with XBODY=0 in WAMIT, 3: Neglect coupling terms between each body and NBODY=1 with XBODY=/0 in WAMIT} (switch) [only used when PotMod=1]
“unused” PotFile - Root name of potential-flow model data; WAMIT output files containing the linear, nondimensionalized, hydrostatic restoring matrix (.hst), frequency-dependent hydrodynamic added mass matrix and damping matrix (.1), and frequency- and direction-dependent wave excitation force vector per unit wave amplitude (.3) (quoted string) [1 to NBody if NBodyMod>1] [MAKE SURE THE FREQUENCIES INHERENT IN THESE WAMIT FILES SPAN THE PHYSICALLY-SIGNIFICANT RANGE OF FREQUENCIES FOR THE GIVEN PLATFORM; THEY MUST CONTAIN THE ZERO- AND INFINITE-FREQUENCY LIMITS!]
1 WAMITULEN - Characteristic body length scale used to redimensionalize WAMIT output (meters) [1 to NBody if NBodyMod>1] [only used when PotMod=1]
0 PtfmRefxt - The xt offset of the body reference point(s) from (0,0,0) (meters) [1 to NBody] [only used when PotMod=1]
0 PtfmRefyt - The yt offset of the body reference point(s) from (0,0,0) (meters) [1 to NBody] [only used when PotMod=1]
0 PtfmRefzt - The zt offset of the body reference point(s) from (0,0,0) (meters) [1 to NBody] [only used when PotMod=1. If NBodyMod=2,PtfmRefzt=0.0]
0 PtfmRefztRot - The rotation about zt of the body reference frame(s) from xt/yt (degrees) [1 to NBody] [only used when PotMod=1]
0 PtfmVol0 - Displaced volume of water when the body is in its undisplaced position (m^3) [1 to NBody] [only used when PotMod=1; USE THE SAME VALUE COMPUTED BY WAMIT AS OUTPUT IN THE .OUT FILE!]
0 PtfmCOBxt - The xt offset of the center of buoyancy (COB) from (0,0) (meters) [1 to NBody] [only used when PotMod=1]
0 PtfmCOByt - The yt offset of the center of buoyancy (COB) from (0,0) (meters) [1 to NBody] [only used when PotMod=1]
---------------------- 2ND-ORDER FLOATING PLATFORM FORCES ---------------------- [unused with WaveMod=0 or 6, or PotMod=0 or 2]
0 MnDrift - Mean-drift 2nd-order forces computed {0: None; [7, 8, 9, 10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be non-zero. If NBody>1, MnDrift /=8]
0 NewmanApp - Mean- and slow-drift 2nd-order forces computed with Newman’s approximation {0: None; [7, 8, 9, 10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be non-zero. If NBody>1, NewmanApp/=8. Used only when WaveDirMod=0]
0 DiffQTF - Full difference-frequency 2nd-order forces computed with full QTF {0: None; [10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be non-zero]
0 SumQTF - Full summation -frequency 2nd-order forces computed with full QTF {0: None; [10, 11, or 12]: WAMIT file to use}
---------------------- PLATFORM ADDITIONAL STIFFNESS AND DAMPING -------------- [unused with PotMod=0 or 2]
0 AddF0 - Additional preload (N, N-m) [If NBodyMod=1, one size 6
NBody x 1 vector; if NBodyMod>1, NBody size 6 x 1 vectors]
0
0
0
0
0
0 0 0 0 0 0 AddCLin - Additional linear stiffness (N/m, N/rad, N-m/m, N-m/rad) [If NBodyMod=1, one size 6NBody x 6NBody matrix; if NBodyMod>1, NBody size 6 x 6 matrices]
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 AddBLin - Additional linear damping(N/(m/s), N/(rad/s), N-m/(m/s), N-m/(rad/s)) [If NBodyMod=1, one size 6NBody x 6NBody matrix; if NBodyMod>1, NBody size 6 x 6 matrices]
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 AddBQuad - Additional quadratic drag(N/(m/s)^2, N/(rad/s)^2, N-m(m/s)^2, N-m/(rad/s)^2) [If NBodyMod=1, one size 6NBody x 6NBody matrix; if NBodyMod>1, NBody size 6 x 6 matrices]
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
---------------------- STRIP THEORY OPTIONS --------------------------------------
0 WaveDisp - Method of computing Wave Kinematics {0: use undisplaced position, 1: use displaced position) } (switch) [If PtfmYMod=1, need WaveDisp=1]
0 AMMod - Method of computing distributed added-mass force. (0: Only and always on nodes below SWL at the undisplaced position. 2: Up to the instantaneous free surface) [overwrite to 0 when WaveMod = 0 or 6 or when WaveStMod = 0 in SeaState]
---------------------- AXIAL COEFFICIENTS --------------------------------------
1 NAxCoef - Number of axial coefficients (-)
AxCoefID AxCd AxCa AxCp AxFDMod AxVnCOff AxFDLoFSc
(-) (-) (-) (-) (-) (-) (-)
1 0.00 0.00 1.00 0 0.00 1.00
---------------------- MEMBER JOINTS -------------------------------------------
2 NJoints - Number of joints (-) [must be exactly 0 or at least 2]
JointID Jointxi Jointyi Jointzi JointAxID JointOvrlp [JointOvrlp= 0: do nothing at joint, 1: eliminate overlaps by calculating super member]
(-) (m) (m) (m) (-) (switch)
1 0.00000 0.00000 -20.00010 1 0
2 0.00000 0.00000 10.00000 1 0
---------------- CYLINDRICAL MEMBER CROSS-SECTION PROPERTIES -------------------
1 NPropSetsCyl - Number of cylindrical member property sets (-)
PropSetID PropD PropThck
(-) (m) (m)
1 6.000 0.060
---------------- RECTANGULAR MEMBER CROSS-SECTION PROPERTIES -------------------
0 NPropSetsRec - Number of rectangular member property sets (-)
MPropSetID PropA PropB PropThck
(-) (m) (m) (m)
-------- SIMPLE CYLINDRICAL-MEMBER HYDRODYNAMIC COEFFICIENTS (model 1) ---------
SimplCd SimplCdMG SimplCa SimplCaMG SimplCp SimplCpMG SimplAxCd SimplAxCdMG SimplAxCa SimplAxCaMG SimplAxCp SimplAxCpMG SimplCb SimplCbMG
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
1.00 1.00 1.00 1.00 1.00 1.00 1.00 0.00 0.00 1.00 1.00 1.00 1.00 1.00
-------- SIMPLE RECTANGULAR-MEMBER HYDRODYNAMIC COEFFICIENTS (model 1) ---------
SimplCdA SimplCdAMG SimplCdB SimplCdBMG SimplCaA SimplCaAMG SimplCaB SimplCaBMG SimplCp SimplCpMG SimplAxCd SimplAxCdMG SimplAxCa SimplAxCaMG SimplAxCp SimplAxCpMG SimplCb SimplCbMG
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 1.0
------ DEPTH-BASED CYLINDRICAL-MEMBER HYDRODYNAMIC COEFFICIENTS (model 2) -------
0 NCoefDpthCyl - Number of depth-dependent cylindrical member coefficients (-)
Dpth DpthCd DpthCdMG DpthCa DpthCaMG DpthCp DpthCpMG DpthAxCd DpthAxCdMG DpthAxCa DpthAxCaMG DpthAxCp DpthAxCpMG DpthCb DpthCbMG
(m) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
------ DEPTH-BASED RECTANGULAR-MEMBER HYDRODYNAMIC COEFFICIENTS (model 2) -------
0 NCoefDpthRec - Number of depth-dependent rectangular member coefficients (-)
Dpth DpthCdA DpthCdAMG DpthCdB DpthCdBMG DpthCaA DpthCaAMG DpthCaB DpthCaBMG DpthCp DpthCpMG DpthAxCd DpthAxCdMG DpthAxCa DpthAxCaMG DpthAxCp DpthAxCpMG DpthCb DpthCbMG
(m) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
------ MEMBER-BASED CYLINDRICAL-MEMBER HYDRODYNAMIC COEFFICIENTS (model 3) ------
0 NCoefMembersCyl - Number of member-based cylindrical member coefficients (-)
MemberID MemberCd1 MemberCd2 MemberCdMG1 MemberCdMG2 MemberCa1 MemberCa2 MemberCaMG1 MemberCaMG2 MemberCp1 MemberCp2 MemberCpMG1 MemberCpMG2 MemberAxCd1 MemberAxCd2 MemberAxCdMG1 MemberAxCdMG2 MemberAxCa1 MemberAxCa2 MemberAxCaMG1 MemberAxCaMG2 MemberAxCp1 MemberAxCp2 MemberAxCpMG1 MemberAxCpMG2 MemberCb1 MemberCb2 MemberCbMG1 MemberCbMG2
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
------ MEMBER-BASED RECTANGULAR-MEMBER HYDRODYNAMIC COEFFICIENTS (model 3) ------
0 NCoefMembersRec - Number of member-based rectangular member coefficients (-)
MemberID MemberCdA1 MemberCdA2 MemberCdAMG1 MemberCdAMG2 MemberCdB1 MemberCdB2 MemberCdBMG1 MemberCdBMG2 MemberCaA1 MemberCaA2 MemberCaAMG1 MemberCaAMG2 MemberCaB1 MemberCaB2 MemberCaBMG1 MemberCaBMG2 MemberCp1 MemberCp2 MemberCpMG1 MemberCpMG2 MemberAxCd1 MemberAxCd2 MemberAxCdMG1 MemberAxCdMG2 MemberAxCa1 MemberAxCa2 MemberAxCaMG1 MemberAxCaMG2 MemberAxCp1 MemberAxCp2 MemberAxCpMG1 MemberAxCpMG2 MemberCb1 MemberCb2 MemberCbMG1 MemberCbMG2
(-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-) (-)
-------------------- MEMBERS -------------------------------------------------
1 NMembers - Number of members (-)
MemberID MJointID1 MJointID2 MPropSetID1 MPropSetID2 MSecGeom MSpinOrient MDivSize MCoefMod MHstLMod PropPot [MCoefMod=1: use simple coeff table, 2: use depth-based coeff table, 3: use member-based coeff table] [ PropPot/=0 if member is modeled with potential-flow theory]
(-) (-) (-) (-) (-) (switch) (deg) (m) (switch) (switch) (flag)
1 1 2 1 1 1 0 0.5000 1 1 FALSE
---------------------- FILLED MEMBERS ------------------------------------------
0 NFillGroups - Number of filled member groups (-) [If FillDens = DEFAULT, then FillDens = WtrDens; FillFSLoc is related to MSL2SWL]
FillNumM FillMList FillFSLoc FillDens
(-) (-) (m) (kg/m^3)
---------------------- MARINE GROWTH -------------------------------------------
0 NMGDepths - Number of marine-growth depths specified (-)
MGDpth MGThck MGDens
(m) (m) (kg/m^3)
---------------------- MEMBER OUTPUT LIST --------------------------------------
0 NMOutputs - Number of member outputs (-) [must be < 10]
MemberID NOutLoc NodeLocs [NOutLoc < 10; node locations are normalized distance from the start of the member, and must be >=0 and <= 1] [unused if NMOutputs=0]
(-) (-) (-)
---------------------- JOINT OUTPUT LIST ---------------------------------------
0 NJOutputs - Number of joint outputs [Must be < 10]
3, 20 JOutLst - List of JointIDs which are to be output (-)[unused if NJOutputs=0]
---------------------- OUTPUT --------------------------------------------------
False HDSum - Output a summary file [flag]
False OutAll - Output all user-specified member and joint loads (only at each member end, not interior locations) [flag]
2 OutSwtch - Output requested channels to: [1=Hydrodyn.out, 2=GlueCode.out, 3=both files]
“ES11.4e2” OutFmt - Output format for numerical results (quoted string) [not checked for validity!]
“A11” OutSFmt - Output format for header strings (quoted string) [not checked for validity!]
---------------------- OUTPUT CHANNELS -----------------------------------------
HydroFxi
HydroFyi
HydroMxi
HydroMyi
HydroMzi
END of output channels and end of file. (the word “END” must appear in the first 3 columns of this line)

4TH - SEASTATE

------- SeaState Input File ----------------------------------------------------
NREL 5.0 MW offshore baseline floating platform input properties for the OC3 Monopile.
False Echo - Echo the input file data (flag)
---------------------- ENVIRONMENTAL CONDITIONS --------------------------------
“default” WtrDens - Water density (kg/m^3)
“default” WtrDpth - Water depth (meters) relative to MSL
“default” MSL2SWL - Offset between still-water level and mean sea level (meters) [positive upward; unused when WaveMod = 6; must be zero if PotMod=1 or 2]
---------------------- SPATIAL DISCRETIZATION ---------------------------------------------------
5 X_HalfWidth – Half-width of the domain in the X direction (m) [>0, NOTE: X[nX] = nXdX, where nX = {-NX+1,-NX+2,…,NX-1} and dX = X_HalfWidth/(NX-1)]
5 Y_HalfWidth – Half-width of the domain in the Y direction (m) [>0, NOTE: Y[nY] = nY
dY, where nY = {-NY+1,-NY+2,…,NY-1} and dY = Y_HalfWidth/(NY-1)]
“default” Z_Depth – Depth of the domain the Z direction (m) relative to SWL [0 < Z_Depth <= WtrDpth+MSL2SWL; “default”: Z_Depth = WtrDpth+MSL2SWL; Z[nZ] = ( COS( nZdthetaZ ) – 1 )Z_Depth, where nZ = {0,1,…NZ-1} and dthetaZ = pi/( 2(NZ-1) )]
2 NX – Number of nodes in half of the X-direction domain (-) [>=2]
2 NY – Number of nodes in half of the Y-direction domain (-) [>=2]
15 NZ – Number of nodes in the Z direction (-) [>=2]
---------------------- WAVES ---------------------------------------------------
2 WaveMod - Incident wave kinematics model {0: none=still water, 1: regular (periodic), 1P#: regular with user-specified phase, 2: JONSWAP/Pierson-Moskowitz spectrum (irregular), 3: White noise spectrum (irregular), 4: user-defined spectrum from routine UserWaveSpctrm (irregular), 5: Externally generated wave-elevation time series, 6: Externally generated full wave-kinematics time series, 7: wave frequency components [option 6 is invalid for PotMod/=0]} (switch)
0 WaveStMod - Model for stretching incident wave kinematics to instantaneous free surface {0: none=no stretching, 1: vertical stretching, 2: extrapolation stretching, 3: Wheeler stretching} (switch) [unused when WaveMod=0 or when PotMod/=0]
600 WaveTMax - Analysis time for incident wave calculations (sec) [unused when WaveMod=0; determines WaveDOmega=2Pi/WaveTMax in the IFFT]
0.25 WaveDT - Time step for incident wave calculations (sec) [unused when WaveMod=0 or 7; 0.1<=WaveDT<=1.0 recommended; determines WaveOmegaMax=Pi/WaveDT in the IFFT]
3 WaveHs - Significant wave height of incident waves (meters) [used only when WaveMod=1, 2, or 3]
10 WaveTp - Peak-spectral period of incident waves (sec) [used only when WaveMod=1 or 2]
“DEFAULT” WavePkShp - Peak-shape parameter of incident wave spectrum (-) or DEFAULT (string) [used only when WaveMod=2; use 1.0 for Pierson-Moskowitz]
0.15708 WvLowCOff - Low cut-off frequency or lower frequency limit of the wave spectrum beyond which the wave spectrum is zeroed (rad/s) [unused when WaveMod=0, 1, 6, or 7]
3.2 WvHiCOff - High cut-off frequency or upper frequency limit of the wave spectrum beyond which the wave spectrum is zeroed (rad/s) [unused when WaveMod=0, 1, 6, or 7]
0 WaveDir - Incident wave propagation heading direction (degrees) [unused when WaveMod=0, 6 or 7]
0 WaveDirMod - Directional spreading function {0: none, 1: COS2S} (-) [only used when WaveMod=2,3, or 4]
1 WaveDirSpread - Wave direction spreading coefficient ( > 0 ) (-) [only used when WaveMod=2,3, or 4 and WaveDirMod=1]
1 WaveNDir - Number of wave directions (-) [only used when WaveMod=2,3, or 4 and WaveDirMod=1; odd number only]
90 WaveDirRange - Range of wave directions (full range: WaveDir +/- 1/2WaveDirRange) (degrees) [only used when WaveMod=2,3,or 4 and WaveDirMod=1]
123456789 WaveSeed(1) - First random seed of incident waves [-2147483648 to 2147483647] (-) [unused when WaveMod=0, 5, or 6]
“RANLUX” WaveSeed(2) - Second random seed of incident waves [-2147483648 to 2147483647] for intrinsic pRNG, or an alternative pRNG: “RanLux” (-) [unused when WaveMod=0, 5, or 6]
TRUE WaveNDAmp - Flag for normally distributed amplitudes (flag) [only used when WaveMod=2, 3, or 4]
“” WvKinFile - Root name of externally generated wave data file(s) (quoted string) [used only when WaveMod=5, 6 or 7]
---------------------- 2ND-ORDER WAVES ----------------------------------------- [unused with WaveMod=0 or 6]
True WvDiffQTF - Full difference-frequency 2nd-order wave kinematics (flag)
True WvSumQTF - Full summation-frequency 2nd-order wave kinematics (flag)
0 WvLowCOffD - Low frequency cutoff used in the difference-frequencies (rad/s) [Only used with a difference-frequency method]
3.04292 WvHiCOffD - High frequency cutoff used in the difference-frequencies (rad/s) [Only used with a difference-frequency method]
0.314159 WvLowCOffS - Low frequency cutoff used in the summation-frequencies (rad/s) [Only used with a summation-frequency method]
3.2 WvHiCOffS - High frequency cutoff used in the summation-frequencies (rad/s) [Only used with a summation-frequency method]
---------------------- CONSTRAINED WAVES ---------------------------------------
0 ConstWaveMod - Constrained wave model: 0=none; 1=Constrained wave with specified crest elevation, alpha; 2=Constrained wave with guaranteed peak-to-trough crest height, HCrest (flag)
1 CrestHmax - Crest height (2*alpha for ConstWaveMod=1 or HCrest for ConstWaveMod=2), must be larger than WaveHs (m) [unused when ConstWaveMod=0]
60 CrestTime - Time at which the crest appears (s) [unused when ConstWaveMod=0]
0 CrestXi - X-position of the crest (m) [unused when ConstWaveMod=0]
0 CrestYi - Y-position of the crest (m) [unused when ConstWaveMod=0]
---------------------- CURRENT ------------------------------------------------- [unused with WaveMod=6]
0 CurrMod - Current profile model {0: none=no current, 1: standard, 2: user-defined from routine UserCurrent} (switch)
0 CurrSSV0 - Sub-surface current velocity at still water level (m/s) [used only when CurrMod=1]
“DEFAULT” CurrSSDir - Sub-surface current heading direction (degrees) or DEFAULT (string) [used only when CurrMod=1]
20 CurrNSRef - Near-surface current reference depth (meters) [used only when CurrMod=1]
0 CurrNSV0 - Near-surface current velocity at still water level (m/s) [used only when CurrMod=1]
0 CurrNSDir - Near-surface current heading direction (degrees) [used only when CurrMod=1]
0 CurrDIV - Depth-independent current velocity (m/s) [used only when CurrMod=1]
0 CurrDIDir - Depth-independent current heading direction (degrees) [used only when CurrMod=1]
---------------------- MacCamy-Fuchs diffraction model -------------------------
0 MCFD - MacCamy-Fuchs member radius (ignored if radius <= 0) [must be 0 when WaveMod 0 or 6]
---------------------- OUTPUT --------------------------------------------------
False SeaStSum - Output a summary file [flag]
2 OutSwtch - Output requested channels to: [1=SeaState.out, 2=GlueCode.out, 3=both files]
“ES11.4e2” OutFmt - Output format for numerical results (quoted string) [not checked for validity!]
“A11” OutSFmt - Output format for header strings (quoted string) [not checked for validity!]
1 NWaveElev - Number of points where the incident wave elevations can be computed (-) [maximum of 9 output locations]
0 WaveElevxi - List of xi-coordinates for points where the incident wave elevations can be output (meters) [NWaveElev points, separated by commas or white space; usused if NWaveElev = 0]
0 WaveElevyi - List of yi-coordinates for points where the incident wave elevations can be output (meters) [NWaveElev points, separated by commas or white space; usused if NWaveElev = 0]
2 NWaveKin - Number of points where the wave kinematics can be output (-) [maximum of 9 output locations]
5, -5 WaveKinxi - List of xi-coordinates for points where the wave kinematics can be output (meters) [NWaveKin points, separated by commas or white space; usused if NWaveKin = 0]
5, -5 WaveKinyi - List of yi-coordinates for points where the wave kinematics can be output (meters) [NWaveKin points, separated by commas or white space; usused if NWaveKin = 0]
-10, -15 WaveKinzi - List of zi-coordinates for points where the wave kinematics can be output (meters) [NWaveKin points, separated by commas or white space; usused if NWaveKin = 0]
---------------------- OUTPUT CHANNELS -----------------------------------------
“Wave1Elev” - Wave elevation at the WAMIT reference point (0,0)
END of output channels and end of file. (the word “END” must appear in the first 3 columns of this line)

I won’t copy the AeroDyn, ServoDyn and SubDyn because the text is already too long.

I couldn’t attach the archives, but if you want I can put then online and share the link. Thanks for your support.

Dear @Matheus.Abreu,

From my quick skim of your input files, the only things I see that are different relative to the MW_OC3Mnpl_DLL_WTurb_WavesIrr files available in the OpenFAST v4.1.2 r-test are the settings of PtfmRIner, PtfmPIner, PtfmYIner, and BldNodes in ElastoDyn. Can you clarify how you calculated your values of PtfmRIner, PtfmPIner, and PtfmYIner and why you reduced BldNodes? I would not expect the original values should need to be changed.

Also, I expect that you should be able to run the original r-test files with OpenFAST v4.1.2 without any issues. If that is not happening, can you clarify how you’ve obtained the executable of OpenFAST v4.1.2?

Best regards,

Thanks for your help @Jason.Jonkman.

The Ptfm R, P, and Y inertias I mentioned above were set to very high values (~E+9) only to verify whether OpenFAST would run correctly, because I realized that the original yaw inertia of the NREL 5 MW turbine (1.534E+6) was the input that triggered the problem with the hydrodynamic forces.

Based on your explanation, I think I now understand the issue. You mentioned that the model should simply become unstable, and I believe this is what caused the errors. With the ~E+9 values for the roll, pitch, and yaw inertias, I post-processed an estimated fatigue life of about 15 years, which is quite low, I think. Afterwards, I ran another simulation using only a yaw inertia of 1E+11, and the simulation completed without errors, although the estimated fatigue life tended to zero. Therefore, I suspect that the platform does not support the environmental conditions as well as I initially expected.

I will proceed with the brazilian simulations that I intend to use in my thesis and evaluate whether the same issues occur under those conditions. I really appreciate your help.

Regarding your last question, I obtained the OpenFAST executable from the OpenFAST GitHub releases page ( Releases · OpenFAST/openfast · GitHub ). As shown below, none of the test cases I downloaded (including 5MW_OC3Mnpl_DLL_WTurb_WavesIrr, as well as other r-tests downloaded earlier this year, and the IEA-15-240-RWT-Monopile case downloaded this week) ran successfully with either OpenFAST 4.1.2 or OpenFAST 4.0.0.

The first error I encountered was:

“Invalid numerical input file while trying to read BldNodes”

After that, I copied the 5MW_OC3Mnpl_DLL_WTurb_WavesIrr test case and modified the input files to resolve the issue. Several additional errors appeared, and I addressed them one by one until the simulation ran successfully.

It seems that these test cases may not have been prepared for the OpenFAST versions I am using, although I understand that they are intended to be compatible. However, I might also be making a mistake when setting up the simulations. To run them, I only downloaded the test cases, OpenFAST_x64.exe, and DISCON.dll.

Please let me know if I can provide any additional information. I apologize if I have not described the errors clearly enough.

Dear @Matheus.Abreu,

I agree that it sounds like using unrealistic values for the platform inertias and number of blade structural analysis nodes is driving the model instability.

It sounds like the original issue is that the input files from the r-test and the precompiled executables you are using are not downloaded for consistent versions. For a given release of OpenFAST and the r-test, the r-test models should be able to run with the precompiled executables without any changes (other than the file paths. depending on where you stored the input files and executables).

Best regards,

Thank you Jonkman, I will try the other releases of OpenFAST.

Best Regards