Error in Co-Simulation: Invalid Numerical Input While Reading Gravity

[Cadulo]

Hello everyone,

When I was running the co-simulation, I encountered the following error:

Run_OpenLoop

---

OpenFAST

Copyright (C) 2023 National Renewable Energy Laboratory
Copyright (C) 2023 Envision Energy USA LTD

This program is licensed under Apache License Version 2.0 and comes with ABSOLUTELY NO WARRANTY.
See the "LICENSE" file distributed with this software for details.

---

OpenFAST-v3.4.1-dirty
Compile Info:

• Compiler: Intel(R) Fortran Compiler 2021
• Architecture: 64 bit
• Precision: single
• OpenMP: No
• Date: Apr 12 2023
• Time: 13:57:40
  Execution Info:
• Date: 05/24/2025
• Time: 18:42:58-0500

OpenFAST input file heading:
Generated with AeroElasticSE FAST driver

OpenFAST completed.

Error using Run_OpenLoop (line 19)
Error reported by S-function 'FAST_SFunc' in 'OpenLoop/FAST Nonlinear Wind Turbine/S-Function':
FAST_InitializeAll:FAST_Init:FAST_ReadPrimaryFile:Invalid numerical input for file "C:/Users/celop/OneDrive - Universidad
internacional de valencia/15 Master Inteligencia Artificial/TRABAJO DE FIN DE MASTER/Open Fast
4.0.2/IEA-3.4-130-RWT-master/openfast/IEA-3.4-130-RWT.fst" occurred while trying to read Gravity.

Does anyone have an idea what could be causing this issue?

Thanks in advance for your help!

This is my fst file:

------- OpenFAST INPUT FILE -------------------------------------------
Generated with AeroElasticSE FAST driver
---------------------- SIMULATION CONTROL --------------------------------------
False Echo - Echo input data to .ech (flag)
"FATAL" AbortLevel - Error level when simulation should abort (string) {"WARNING", "SEVERE", "FATAL"}
600.0 TMax - Total run time (s)
0.025 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}
99999.0 DT_UJac - Time between calls to get Jacobians (s)
1000000.0 UJacSclFact - Scaling factor used in Jacobians (-)
---------------------- FEATURE SWITCHES AND FLAGS ------------------------------
1 CompElast - Compute structural dynamics (switch) {1=ElastoDyn; 2=ElastoDyn + BeamDyn for blades; 3=Simplified ElastoDyn}
1 CompInflow - Compute inflow wind velocities (switch) {0=still air; 1=InflowWind; 2=external from ExtInflow}
2 CompAero - Compute aerodynamic loads (switch) {0=None; 1=AeroDisk; 2=AeroDyn; 3=ExtLoads}
1 CompServo - Compute control and electrical-drive dynamics (switch) {0=None; 1=ServoDyn}
0 CompSeaSt - Compute sea state information (switch) {0=None; 1=SeaState}
0 CompHydro - Compute hydrodynamic loads (switch) {0=None; 1=HydroDyn}
0 CompSub - Compute sub-structural dynamics (switch) {0=None; 1=SubDyn; 2=External Platform MCKF}
0 CompMooring - Compute mooring system (switch) {0=None; 1=MAP++; 2=FEAMooring; 3=MoorDyn; 4=OrcaFlex}
0 CompIce - Compute ice loads (switch) {0=None; 1=IceFloe; 2=IceDyn}
0 MHK - MHK turbine type (switch) {0=Not an MHK turbine; 1=Fixed MHK turbine; 2=Floating MHK turbine}
---------------------- ENVIRONMENTAL CONDITIONS --------------------------------
9.81 Gravity - Gravitational acceleration (m/s^2)
1.225 AirDens - Air density (kg/m^3)
1025 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 (Pa) [used only for an MHK turbine cavitation check]
1700 Pvap - Vapour pressure of working fluid (Pa) [used only for an MHK turbine cavitation check]
300 WtrDpth - Water depth (m)
0 MSL2SWL - Offset between still-water level and mean sea level (m) [positive upward]
---------------------- INPUT FILES ---------------------------------------------
"IEA-3.4-130-RWT_ElastoDyn.dat" EDFile - Name of file containing ElastoDyn input parameters (quoted string)
"IEA-3.4-130-RWT_BeamDyn.dat" BDBldFile(1) - Name of file containing BeamDyn input parameters for blade 1 (quoted string)
"IEA-3.4-130-RWT_BeamDyn.dat" BDBldFile(2) - Name of file containing BeamDyn input parameters for blade 2 (quoted string)
"IEA-3.4-130-RWT_BeamDyn.dat" BDBldFile(3) - Name of file containing BeamDyn input parameters for blade 3 (quoted string)
"IEA-3.4-130-RWT_InflowFile.dat" InflowFile - Name of file containing inflow wind input parameters (quoted string)
"IEA-3.4-130-RWT_AeroDyn15.dat" AeroFile - Name of file containing aerodynamic input parameters (quoted string)
"IEA-3.4-130-RWT_ServoDyn.dat" ServoFile - Name of file containing control and electrical-drive input parameters (quoted string)
"none" SeaStFile - Name of file containing sea state input parameters (quoted string)
"none" HydroFile - Name of file containing hydrodynamic input parameters (quoted string)
"none" SubFile - Name of file containing sub-structural input parameters (quoted string)
"none" MooringFile - Name of file containing mooring system input parameters (quoted string)
"none" IceFile - Name of file containing ice input parameters (quoted string)
---------------------- OUTPUT --------------------------------------------------
False SumPrint - Print summary data to ".sum" (flag)
10.0 SttsTime - Amount of time between screen status messages (s)
99999.0 ChkptTime - Amount of time between creating checkpoint files for potential restart (s)
default DT_Out - Time step for tabular output (s) (or "default")
0.0 TStart - Time to begin tabular output (s)
3 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)
0.0 Twr_Kdmp - Damping factor for the tower [used only if CalcSteady=True] (N/(m/s))
0.0 Bld_Kdmp - Damping factor for the blades [used only if CalcSteady=True] (N/(m/s))
2 NLinTimes - Number of times to linearize (-) [>=1] [unused if Linearize=False]
30.000000, 60.000000 LinTimes - List of times at which to linearize (s) [1 to NLinTimes] [used only when Linearize=True and CalcSteady=False]
1 LinInputs - Inputs included in linearization (switch) {0=none; 1=standard; 2=all module inputs (debug)} [unused if Linearize=False]
1 LinOutputs - Outputs included in linearization (switch) {0=none; 1=from OutList(s); 2=all module outputs (debug)} [unused if Linearize=False]
False LinOutJac - Include full Jacobians in linearization output (for debug) (flag) [unused if Linearize=False; used only if LinInputs=LinOutputs=2]
False LinOutMod - Write module-level linearization output files in addition to output for full system? (flag) [unused if Linearize=False]
---------------------- VISUALIZATION ------------------------------------------
0 WrVTK - VTK visualization data output: (switch) {0=none; 1=initialization data only; 2=animation}
2 VTK_type - Type of VTK visualization data: (switch) {1=surfaces; 2=basic meshes (lines/points); 3=all meshes (debug)} [unused if WrVTK=0]
False VTK_fields - Write mesh fields to VTK data files? (flag) {true/false} [unused if WrVTK=0]
10.0 VTK_fps - Frame rate for VTK output (frames per second){will use closest integer multiple of DT} [used only if WrVTK=2]

[jjonkman]

Dear @Cadulo,

As with any input file processing error, I would enable the Echo option to debug errors in input file formatting.

Best regards,

[cktmdgus63]

Hello,

I also tried the Echo option but I still have some error message

[jjonkman]

Dear @cktmdgus63,

Can you share the Echo file corresponding to your OpenFAST primary (.fst) input file?

Best regards,

[JianingFu-EXE]

Dear Jonkman,

I have the same problem and the Echo file stops before the ENVIRONMENTAL CONDITIONS. The echo file is as

---

This file of echoed input was generated by OpenFAST on 10-Sep-2025 at 15:52:53.

Data from OpenFAST primary input file "5MW_ITIBarge_DLL_WTurb_WavesIrr.fst":

           FTitle         - File Header: File Description (line 2)

"FAST Certification Test #22: NREL 5.0 MW Baseline Wind Turbine with ITI Barge Configuration, for use in offshore analysis"

        T  Echo           - Echo input data to <RootName>.ech (flag)
           AbortLevel     - Error level when simulation should abort (string)

"FATAL"
6.0000E+01 TMax - Total run time (s)
1.2500E-02 DT - Recommended module time step (s)
2 InterpOrder - Interpolation order for inputs and outputs {0=nearest neighbor ,1=linear, 2=quadratic} (-)
0 NumCrctn - Number of corrections{0=explicit calculation, i.e., no corrections} (-)
9.9999E+04 DT_UJac - Time between calls to get Jacobians (s)
1.0000E+06 UJacSclFact - Scaling factor used in Jacobians (-)

        1  CompElast      - Compute structural dynamics (switch) {1=ElastoDyn; 2=ElastoDyn + BeamDyn for blades}
        1  CompInflow     - inflow wind velocities (switch) {0=still air; 1=InflowWind}
        2  CompAero       - Compute aerodynamic loads (switch) {0=None; 1=AeroDyn}
        1  CompServo      - Compute control and electrical-drive dynamics (switch) {0=None; 1=ServoDyn}
        1  CompHydro      - Compute hydrodynamic loads (switch) {0=None; 1=HydroDyn}
        1  CompSub        - Compute sub-structural dynamics (switch) {0=None; 1=SubDyn}
        0  CompMooring    - Compute mooring system (switch) {0=None; 1=MAP; 2=FEAMooring; 3=MoorDyn; 4=OrcaFlex}
        1  CompIce        - Compute ice loads (switch) {0=None; 1=IceFloe}
        0  MHK            - MHK turbine type (switch) {0=Not an MHK turbine; 1=Fixed MHK turbine; 2=Floating MHK turbine}

[jjonkman]

Dear @JianingFu-EXE,

You haven't shared your corresponding OpenFAST primary (.fst) input file, but I'm guessing your input file is formatted for a newer version of OpenFAST than you are running. My guess is your input file has the CompSeaSt switch, but the version you are using is before OpenFAST v4.0 when input CompSeaSt was added.

Best regards,