Dear @Jason.Jonkman,
Hope you are doing well. I have a basic question 
Up to now, i did not get the difference between steady and uniform wind speed. (What i know is that wind speed can change with height according to some laws and i know also that turbsim generates stochastic wind field that changes with time and space (z and y directions))
Best Regards,
Riad
Dear @Riad.Elhamoud,
In InflowWind, by “turbulence”, we mean that the flow varies both in space and time. By “uniform”, we mean spatially coherent (perhaps with a shear profile) and time varying. By “steady” we mean both spatially coherent (perhaps with shear profile) and time invariant.
Best regards,
Dear @Jason.Jonkman ,
I am trying to simulate an uniform wind profile.
But I am getting confused in generating it.
A) In order to generate this, I made the turbulence moel as ‘NONE’ and specified the URef in TurbSim input file. But I am getting an error:’ M:\coh_events\eventdata not found’. Is this the correct method to generate the uniform wind.bts file that has to be given as an input in the InFlowWind in OpenFAST?
B) In order to generate the steady wind profile, I have changed the windtype and HWindSpeed in InflowWind. Is this the correct method ?
Please help me to understand the methods of generating uniform and steady wind profiles in TurbSim and InflowWind better.
Thanks,
Dear @Arya.Thomas,
I think maybe i could help. Here my answers for your questions.
A) When i want to generate uniform wind profile, i set Windtype in InflowWind input file to 2. Then, i copy the path of a file (which has .wnd extension) and paste it in line 17.
B) For the steadywind, i simply set WindType in InflowWind to 1 and i change the related parameter in lines 14 and 15.
Hope that may help you.
Best Regards,
Riad
Thanks @Riad.Elhamoud ,
It is a useful information.
But from where can the .wnd file be generated? If its from TurbSim, can you share what all parameters have to be changed in TurbSim.inp to get the unifrom wind.wnd file?
Regards,
Dear @Arya.Thomas,
Not at all !
You could find an example of the .wnd file in r-test/glue-codes/openfast/SWRT/Wind at b63e9280234c2fb5695a37931d2329f3011e97ec · OpenFAST/r-test · GitHub
Best Regards,
Riad
Dear @Arya.Thomas,
I agree with @Riad.Elhamoud’s responses. Given its simple format, the uniform wind (.wnd) file can be generated by hand (you don’t need TurbSim for that). The old IECWind utility (IECWind | Wind Research | NREL) can also be used to generate uniform wind files for the simple deterministic gusts (ECD, EDC, EOG, etc.) specified within the IEC design standards.
Best regards,
Thank you @Riad.Elhamoud and @Jason.Jonkman
I have tried generating the .wnd file and ran a simulation. The case is a 11.4m/s wind velocity for a random wave condition. But I am getting an error (numerical instability):
OpenFAST
Copyright (C) 2021 National Renewable Energy Laboratory
Copyright (C) 2021 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-v3.0.0
Compile Info:
OpenFAST input file heading:
FAST Certification Test #24: NREL 5.0 MW Baseline Wind Turbine with OC3 Hywind Configuration,
for use in offshore analysis
Running ElastoDyn.
Nodal outputs section of ElastoDyn input file not found or improperly formatted.
Running AeroDyn.
AD15 Nodal Outputs: Nodal output section of AeroDyn input file not found or improperly formatted.
Skipping nodal outputs.
Running InflowWind.
Running ServoDyn.
Running ServoDyn Interface for Bladed Controllers (using Intel Visual Fortran for Windows, ).
Using legacy Bladed DLL interface.
Running HydroDyn.
Generating incident wave kinematics and current time history.
Reading in WAMIT output with root name
“E:/Software_setups/OpenFAST/openfast-3.0.0/O2_R1_11.4_Uniform/5MW_Baseline/HydroData/Spar”.
Computing radiation impulse response functions and wave diffraction forces.
Running MoorDyn (v1.01.02F, 8-Apr-2016).
MD_Init: Opening MoorDyn input file:
E:/Software_setups/OpenFAST/openfast-3.0.0/O2_R1_11.4_Uniform/5MW_Baseline/NRELOffshrBsline5MW_O
C3Hywind_MoorDyn.dat
Creating mooring system. 3 fairleads, 3 anchors, 0 connects.
Finalizing ICs using dynamic relaxation.
t=30 FairTen 1: 9.09637E+05, 9.10293E+05, 9.10416E+05
Fairlead tensions converged to 0.1% after 30 seconds.
FAST_InitializeAll: IfW_Init:IfW_UniformWind_Init: Could not read upflow column in uniform wind
files. Assuming upflow is 0.
Time: 0 of 3600 seconds.
FAST_Solution0:CalcOutputs_And_SolveForInputs:SolveOption2:SrvD_CalcOutput:DLL_controller_call:Run
ning with torque and pitch control of the NREL offshore 5MW baseline wind turbine from DISCON.dll
as written by J. Jonkman of NREL/NWTC for use in the IEA Annex XXIII OC3 studies. Includes
modifications for the Hywind spar.
FAST_Solution:CalcOutputs_And_SolveForInputs:SolveOption1:ED_HD_InputOutputSolve:HydroDyn_CalcOutp
ut: Angles in GetSmllRotAngs() are larger than 0.4 radians.
HydroDyn_CalcOutput: Angles in GetSmllRotAngs() are larger than 0.4 radians.
HydroDyn_CalcOutput:HDOut_MapOutputs: Angles in GetSmllRotAngs() are larger than 0.4 radians.
ED_HD_InputOutputSolve:HydroDyn_CalcOutput: Angles in GetSmllRotAngs() are larger than 0.4
radians.
HydroDyn_CalcOutput: Angles in GetSmllRotAngs() are larger than 0.4 radians.
HydroDyn_CalcOutput:HDOut_MapOutputs: Angles in GetSmllRotAngs() are larger than 0.4 radians.
FAST_Solution:FAST_AdvanceStates:ED_ABM4:ED_CalcContStateDeriv:LAPACK_DGETRF: U( 20,
20)=0. Factor U is exactly singular.
OpenFAST encountered an error at simulation time 0.7 of 3600 seconds.
Simulation error level: FATAL ERROR
Aborting OpenFAST.
Can @Jason.Jonkman or/and @Riad.Elhamoud help me to resolve this?
Thanks,
Dear @Arya.Thomas,
Sorry, i have no idea. I haven’t encountered this problem before. Only @Jason.Jonkman can help getting you out 
Best Regards,
Riad
Dear @Arya.Thomas,
It looks like you are simulating the NREL 5-MW baseline wind turbine atop the OC3-Hywind spar. Presumably you are using the OpenFAST model from the r-test (r-test/glue-codes/openfast/5MW_OC3Spar_DLL_WTurb_WavesIrr at main · OpenFAST/r-test · GitHub); is that correct? Can you clarify what you changed in the input file(s) of this model other than the WindType and uniform wind file?
Best regards,