FAST - Warning: tower model/possible tower strike

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Rui.Hao
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Re: FAST - Warning: tower model/possible tower strike

Postby Rui.Hao » Tue Jan 19, 2021 3:19 am

Dear Jason

I set PCmode to 5 , it works well.
:cry: :cry: :cry:

Best regards!

Jason.Jonkman
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Re: FAST - Warning: tower model/possible tower strike

Postby Jason.Jonkman » Tue Jan 19, 2021 6:29 am

Dear Rui.Hao,

You shouldn't need to change the time step to be smaller than 0.0125 s for the OC3-Hywind model , unless you change the structural properties (mass, stiffness, or geometry).

If PCMode = VSContrl = 5 works well while PCMode = VSContrl = 4 does not, this sounds like a problem in how you've defined the controller in Simulink, or the lack of any control in Simulink if you've not set that.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Satish.Jawalageri
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Re: FAST - Warning: tower model/possible tower strike

Postby Satish.Jawalageri » Mon Feb 01, 2021 3:55 am

Dear Jason,

I am running analysis for 15MW turbine for IEC load case DLC 6.3 (EWM01) in IECWind, I have considered NacYaw = 8deg, and I am getting the following error (attached the input files).

Code: Select all

FAST_Solution:FAST_AdvanceStates:AD_UpdateStates:BEMT_UpdateStates(node 49, blade
1):UA_UpdateStates:UA_UpdateDiscOtherState:ComputeKelvinChain:Mach number exceeds 0.3. Theory is
invalid. This warning will not be repeated though the condition may persist.


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(): 0.485 s
 Time: 1 of 90 seconds. Estimated final completion at 11:03:58.

FAST_Solution:FAST_AdvanceStates:AD_UpdateStates:SetInputs:TwrInfl:getLocalTowerProps:Tower
strike.

 FAST encountered an error at simulation time 1.1 of 90 seconds.
 Simulation error level: FATAL ERROR

 Aborting OpenFAST.


Thanks,
Satish J
Attachments
IEA-15-240-RWT-Monopile_Ip_FIles.zip
(9.64 KiB) Downloaded 30 times

Jason.Jonkman
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Re: FAST - Warning: tower model/possible tower strike

Postby Jason.Jonkman » Mon Feb 01, 2021 10:23 am

Dear Satish,

IEC load case DLC 6.3 involves the modeling of a parked/idling turbine, not an operational wind turbine. It looks like you are applying a very high wind speed, but are keeping the rotor speed, blade-pitch, and controller operational. I would think you'd want to set up your model in a parked/idling condition without active control.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Satish.Jawalageri
Posts: 117
Joined: Sun May 31, 2020 4:57 am
Organization: University College Dublin
Location: Ireland

Re: FAST - Warning: tower model/possible tower strike

Postby Satish.Jawalageri » Mon Feb 01, 2021 10:58 am

Dear Jason,

Thanks for your reply.

I have run the analysis by considering parked condition. I am getting following error and I have attached the input files.

Code: Select all

FAST_InitializeAll:FAST_Init:FAST_ReadPrimaryFile:1/VTK_fps is not an integer multiple of DT.
FAST will output VTK information at 15.385 fps, the closest rate possible.
FAST_InitializeAll: IfW_Init:IfW_UniformWind_Init: Only 1 line in uniform wind file. Steady,
horizontal wind speed at the hub height is 56 m/s.

 Time: 0 of 90 seconds.

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(): 6.00000E-02 s


FAST_Solution:FAST_AdvanceStates:SolveOption2c_Inp2AD_SrvD:InflowWind_CalcOutput:CalcOutput:IfW_Un
iformWind_CalcOutput:GetWindSpeed:Height must not be negative. Error calculating the wind speed
at position (-55.591, 143.95, -127.67) in the wind-file coordinates

 FAST encountered an error at simulation time 6.00000E-02 of 90 seconds.
 Simulation error level: FATAL ERROR

 Aborting OpenFAST.


Thanks,
Satish J
Attachments
IEA-15-240-RWT-Monopile_Parked.zip
(9.65 KiB) Downloaded 26 times

Jason.Jonkman
Posts: 5762
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
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Re: FAST - Warning: tower model/possible tower strike

Postby Jason.Jonkman » Mon Feb 01, 2021 11:18 am

Dear Satish,

I generally agree with how you've set your idling wind turbine, except that you've engaged the Thevenin-equivalent induction generator at time zero in ServoDyn. You should disable the generator / torque controller altogether by setting GenTIStr = TRUE with TimGenOn > TMax.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Satish.Jawalageri
Posts: 117
Joined: Sun May 31, 2020 4:57 am
Organization: University College Dublin
Location: Ireland

Re: FAST - Warning: tower model/possible tower strike

Postby Satish.Jawalageri » Tue Feb 02, 2021 2:31 am

Dear Jason,

Thanks for your reply.

I am getting the same error even if I change the above suggested (attached the servodyn input file).

Code: Select all

FAST_InitializeAll:FAST_Init:FAST_ReadPrimaryFile:1/VTK_fps is not an integer multiple of DT.
FAST will output VTK information at 15.385 fps, the closest rate possible.
FAST_InitializeAll: IfW_Init:IfW_UniformWind_Init: Only 1 line in uniform wind file. Steady,
horizontal wind speed at the hub height is 56 m/s.

 Time: 0 of 90 seconds.

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(): 6.00000E-02 s


FAST_Solution:FAST_AdvanceStates:SolveOption2c_Inp2AD_SrvD:InflowWind_CalcOutput:CalcOutput:IfW_Un
iformWind_CalcOutput:GetWindSpeed:Height must not be negative. Error calculating the wind speed
at position (-55.591, 143.81, -127.53) in the wind-file coordinates

 FAST encountered an error at simulation time 6.00000E-02 of 90 seconds.
 Simulation error level: FATAL ERROR

 Aborting OpenFAST.


Thanks,
Satish J
Attachments
IEA-15-240-RWT-Monopile_ServoDyn.rtf
(11.93 KiB) Downloaded 23 times

Jason.Jonkman
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Re: FAST - Warning: tower model/possible tower strike

Postby Jason.Jonkman » Tue Feb 02, 2021 6:58 am

Dear Satish,

I also noticed that you've set the initial nacelle-yaw angle to NacYaw = 8deg in ElastoDyn, but you've set the neutral yaw position in ServoDyn to be YawNeut = 0deg. This will cause the nacelle-yaw angle to quickly snap back to 0deg and result in unrealistic loads and deflections. If you want to keep the nacelle at 8deg and keep the nacelle-yaw DOF enabled (YawDOF = TRUE), then set YawNeut = 8deg as well.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Satish.Jawalageri
Posts: 117
Joined: Sun May 31, 2020 4:57 am
Organization: University College Dublin
Location: Ireland

Re: FAST - Warning: tower model/possible tower strike

Postby Satish.Jawalageri » Tue Feb 02, 2021 8:19 am

Dear Jason,

Thanks for your reply.

1. Still I am getting error after changing.

Code: Select all

FAST_InitializeAll:FAST_Init:FAST_ReadPrimaryFile:1/VTK_fps is not an integer multiple of DT.
FAST will output VTK information at 15.385 fps, the closest rate possible.
FAST_InitializeAll: IfW_Init:IfW_UniformWind_Init: Only 1 line in uniform wind file. Steady,
horizontal wind speed at the hub height is 56 m/s.

 Time: 0 of 90 seconds.

FAST_Solution:FAST_AdvanceStates:SolveOption2c_Inp2AD_SrvD:InflowWind_CalcOutput:CalcOutput:IfW_Un
iformWind_CalcOutput:GetWindSpeed:Height must not be negative. Error calculating the wind speed
at position (51.995, -161.71, -2.6111) in the wind-file coordinates

 FAST encountered an error at simulation time 7.00000E-02 of 90 seconds.
 Simulation error level: FATAL ERROR

 Aborting OpenFAST.


2. As I am running DLC 6.3, instead of using the IECWind, I used Turbisim, but I am still getting following error and I have attached the turbsim and inflow file.

Code: Select all

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(): 6.50000E-02 s


FAST_Solution:FAST_AdvanceStates:SolveOption2c_Inp2AD_SrvD:InflowWind_CalcOutput:CalcOutput:IfW_TS
FFWind_CalcOutput [position=(-1040.4, 3272.6, -874.5) in wind-file coordinates]: FF wind array
boundaries violated. Grid too small in Z direction (height (Z=-874.5 m) is below the grid and no
tower points are defined).

 FAST encountered an error at simulation time 6.50000E-02 of 90 seconds.
 Simulation error level: FATAL ERROR

 Aborting OpenFAST.


Thanks and regards,
Satish J
Attachments
IEA-15-240-RWT_InflowFile_Turbsim.zip
(4.13 KiB) Downloaded 23 times

Jason.Jonkman
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Location: Boulder, CO
Contact:

Re: FAST - Warning: tower model/possible tower strike

Postby Jason.Jonkman » Tue Feb 02, 2021 9:28 am

Dear Satish,

Well, clearly your model is going numerically unstable very quickly. You've changed the input file a couple times no, so, it may be useful to share what you are running now. Regardless, something is clearly not set up correctly and I would suggest simplifying the model to debug. Does the model run if you disable aerodynamics altogether? How about if you disable structural degrees of freedom? Or reduce the time step?

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Satish.Jawalageri
Posts: 117
Joined: Sun May 31, 2020 4:57 am
Organization: University College Dublin
Location: Ireland

Re: FAST - Warning: tower model/possible tower strike

Postby Satish.Jawalageri » Thu Feb 04, 2021 10:33 am

Dear Jason,

Thanks for the reply.

It is working well when I reduce the time step, thanks a lot! Could I know what might be the reason for running normally when I reduce the time step.

Thanks,
Satish J

Jason.Jonkman
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Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
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Re: FAST - Warning: tower model/possible tower strike

Postby Jason.Jonkman » Thu Feb 04, 2021 10:42 am

Dear Satish,

Typically the time step requirements are dictated by the structural properties (mass, stiffness, or geometry) (see related forum topics on this subject). Again, I'm not sure I understand everything you've changed in the model.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Satish.Jawalageri
Posts: 117
Joined: Sun May 31, 2020 4:57 am
Organization: University College Dublin
Location: Ireland

Re: FAST - Warning: tower model/possible tower strike

Postby Satish.Jawalageri » Thu Feb 04, 2021 12:03 pm

Dear Jason,

Thanks for your reply.

I have attached the input files for IEC DLC case 6.3 with -20deg yaw misalignment. Could you please advice on whether I have changed everything correct or not.


Thanks,
Satish J
Attachments
IEA-15-240-RWT-Monopile_Ip.zip
(13.26 KiB) Downloaded 28 times

Jason.Jonkman
Posts: 5762
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: FAST - Warning: tower model/possible tower strike

Postby Jason.Jonkman » Thu Feb 04, 2021 3:51 pm

Dear Satish,

Yes, your simulation set-up looks good to me.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov


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