Thanks @Garrett.Barter. I will try and see. On another note, it is possible to get the input files for version compatible with OpenFAST v2.6.0? I have been trying to locate them without success.
Thank you.
Regards,
AOAW
Hi @Garrett.Barter I just checked and I am using the latest version of the files that I found on GitHub. However, the tower strike problem still persisted.
Regards,
AOAW
@Garrett.Barter this is the error that I am now getting:
FAST_Solution:CalcOutputs_And_SolveForInputs:SolveOption2:RotCalcOutput:BEMT_CalcOutput(node 50,
blade 2):UA_CalcOutput:Mach number exceeds 1.0. Equations cannot be evaluated.
** OpenFAST encountered an error at simulation time 160.58 of 1800 seconds.**
** Simulation error level: FATAL ERROR**
Regards,
AOAW
Hello Andre,
For older versions of the OpenFAST input file, you can either take the current release and edit the inputs following the API changes documented here. If you want to access prior versions of the IEA Wind 15-MW, you can find the older v1.0 files here. However, all of the inconsistencies that were addressed in the recent update will return if you use the older files.
For the tower strike, it sounds like you aren’t properly loading the ROSCO controller. Are you on Windows / Mac / Linux? Make sure you edit the ServoDyn.dat file to point to the libdiscon dll-file for Windows, dylib-file for Mac, or so-file for Linux. Are you running the fixed-bottom or floating case? If ROSCO is getting loaded properly, you might need to post some of the relevant files from your setup.
Cheers,
Garrett
Thanks @Garrett.Barter. I am using the older version and so far it is running at the higher wind speeds. I have tested up to 35 m/s turbulent wind. I am however getting a warning about the
"The BEM solution is being turned off due to low TSR. (TSR = 1.9721). This warning will not be
repeated though the condition may persist. (See GeomPhi output channel.)"
So I query as follows:
- How critical is this error, can I overlook it?
- Has a solution to it been found?
Thank you.
Regards,
AOAW
Dear @Andre.White,
Are you running simulations with the turbine operating at 35 m/s or is the turbine parked/idling? 35 m/s is beyond the typical operational range of the IEA Wind 15-MW reference wind turbine.
If you are modeling this condition with the turbine operating, I would expect the TSR to be quite low, where the BEM solution may not be valid. I wouldn’t be too concerned about the warning, but I would question whether it is wise to run an operational condition at 35 m/s.
If you are modeling a parked/idling turbine, you should disable BEM anyway.
Best regards,
Hi @Jason.Jonkman thank you. It is actually for the parked/idling condition but to be honest I have not disabled the BEM.
1) Is the TSR low at this higher wind speed because rotor turns faster?
2) Can you please say what else should I consider/disable when modelling the parked/idling condition? It is extreme environemntal conditions due to hurricanes, so wind speed is quite high. It goes up to about 42 m/s.
Regards,
AOAW
Hi @Jason.Jonkman one more query.
-
How do you disable the BEM?
I checked AeroDyn but can’t see which option disbales it.
Thank you.
Regards,
AOAW
Dear @Andre.White,
See the AeroDyn documentation here for information on how to set up AeroDyn to model a parked/idling rotor: 4.2.1.4. Modeling Considerations — OpenFAST v3.3.0 documentation.
I would not expect much rotor rotation in the idling condition. Have you also disabled the generator and controller (in ServoDyn, PCMode = VSContrl = 0, GenTiStr = True with TimGenOn > TMax) and feathered the blades (BlPitch(1-3) in ElastoDyn = 90deg)?
Best regards,
Hi @Jason.Jonkman I have two queries:
- Is it only in the HyroDyn that you can alter the random seeds? I want to run a simulation for different wind directions, so I am thinking that I will alter the seeds from HydroDyn so that for each wind direction there are x, number of seeds, say.
- Can you use any number for the seeds once it falls within the allowable limits, so can I use 1 to 6 for six seeds?
Thank you.
Regards,
AOAW
Dear @Andre.White,
I’m not sure I understand your first question. The seed set in HydroDyn is for the generating of the sea state. Turbulent wind data is likely defined as a preprocessing step before running OpenFAST, e.g., using TurbSim. You also enter seeds in TurbSim.
Yes, the values of WaveSeed(1-2) in HydroDyn can be any integer between -2147483648 to 2147483647.
Best regards,
Hi @Jason.Jonkman I am trying to model the parked/idle turbine condition. When the wind direction is 0 the model runs in OpenFAST successfully. However, when I change it to, say 30, 60, 90… etc I receive the following error:
FAST_Solution:FAST_AdvanceStates:ED_ABM4:ED_CalcContStateDeriv:SetCoordSy:Small angle assumption violated in SUBROUTINE SmllRotTrans() due to a large blade deflection (ElastoDyn SetCoordSy). The solution may be inaccurate. Simulation continuing, but future warnings from SmllRotTrans() will be suppressed.
Additional debugging message from SUBROUTINE SmllRotTrans(): 0.35 sTime: 530 of 3600 seconds. Estimated final completion at 12:50:14.
FAST_Solution:FAST_AdvanceStates:AD_UpdateStates:SetDisturbedInflow:TwrInfl:getLocalTowerProps:Tower strike.
I am using a turbulent wind speed of 45 m/s. I have attached AeroDyn, ElastoDyn and ServoDyn files so you can see the settings that I used.
Do you have any ideas how I can fix this tower strike error? It seems as if the blade deflections are too great and are therefore conflicting with the tower when the wind direction goes above 0.
Regards,
AOAW
Dear @Andre.White,
At certain yaw errors in the idling condition, a known blade-edgewise instability exists, e.g., as discussed in the following forum topic: Designing for yaw errors using FAST - #7 by Jason.Jonkman.
Note that in the parked/idling condition, I would expect that you’d set the initial rotor speed in ElastoDyn to zero (RotSpeed = 0).
Best regards,
Hi @ Jason I am still trying to troubleshoot this tower strike issue for a turbulent wind speed of 45 m/s. When I use a wind direction of 0 degrees the model runs satisfactory. However, when I increase wind direction to 5 degrees I get the following error:
FAST_Solution:FAST_AdvanceStates:SolveOption2c_Inp2AD_SrvD:InflowWind_CalcOutput:CalcOutput:IfW_FFWind_CalcOutput [position=(15.261, -157.47, 155.48) in wind-file coordinates]: FF wind array boundaries violated: Grid too small in Y direction. Y=-157.47; Y boundaries = [-147.5, 147.5]
This seems like the deflection on the blade is large and so the blade shifts out of the parameters of the grid.
When wind direction increases to 30 degrees I get the tower strike error. See below for reminder:
FAST_Solution:FAST_AdvanceStates:AD_UpdateStates:SetDisturbedInflow:TwrInfl:getLocalTowerProps:Tower strike. OpenFAST encountered an error at simulation time 62.3 of 3600 seconds.Simulation error level: FATAL ERROR
The increased angle seemed to have made the blade deflection even worse producing a tower strike.
My specific question is:
1) Is there anything that I can do to reduce the blade deflection to prevent errors above?
Regards,
AOAW
Dear @Andre.White,
Have you verified that it is the blade-edgewise instability I referred to in my prior post? E.g., is the rotor speed remaining near zero while the blade deflection (and perhaps the tower deflection) grow exponentially? Does increasing the blade edgewise structural damping eliminate the instability?
Best regards,
Hi @Jason.Jonkman increasing the blade-edgewise structural damping seems to have eliminated the instability. I had to use a value as high as 4.5 % for the instability to be removed. I will test a few more cases to be sure.
Thank you.
Regards,
AOAW
1 Like
Hi @Jason.Jonkman so I tested another case and received this error close to the end of the simulation (see below). I have changed the blade-edge structural damping to as high as 60 % but that still did not solve the problem. I also tried to change the blade edge DOF but that did not solve the problem either.
FAST_Solution:FAST_AdvanceStates:SolveOption2c_Inp2AD_SrvD:InflowWind_CalcOutput:CalcOutput:IfW_FF
Wind_CalcOutput [position=(64.311, -157.4, 189.55) in wind-file coordinates]: FF wind array
boundaries violated: Grid too small in Y direction. Y=-157.4; Y boundaries = [-147.5, 147.5] OpenFAST encountered an error at simulation time 2830.8 of 3600 seconds. Simulation error level: FATAL ERROR
Thank you.
Regards,
AOAW