Turning off Unsteady aerodynamics and no valid value of phi.

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Dhaneesh.Machavarapu
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Location: INDIA

Turning off Unsteady aerodynamics and no valid value of phi.

Postby Dhaneesh.Machavarapu » Wed Mar 18, 2020 3:31 am

Sir,

I was working on monopile supported offshore wind turbine using FASTv8. When I was trying to run it FAST was aborting.


Running FAST (v8.16.00a-bjj, 27-Jul-2016), compiled as a 32-bit application using single
precision
linked with NWTC Subroutine Library (v2.09.00, 23-Jul-2016)

Heading of the FAST input file:
FAST Certification Test #19: NREL 5.0 MW Baseline Wind Turbine with OC3 Monopile RF
Configuration, for use in offshore analysis

Running ElastoDyn (v1.04.00a-bjj, 26-Jul-2016).

Running BeamDyn (v1.01.04, 26-Jul-2016).

Running BeamDyn (v1.01.04, 26-Jul-2016).

Running BeamDyn (v1.01.04, 26-Jul-2016).

Running AeroDyn (v15.03.00, 27-Jul-2016).

Running AirfoilInfo (v1.01.00a-bjj, 5-Apr-2016).

Running BEM (v1.02.00, 29-Jun-2016).
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. BladeNode = 1, Blade = 1
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. BladeNode = 2, Blade = 1
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. BladeNode = 3, Blade = 1
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. BladeNode = 4, Blade = 1
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. BladeNode = 1, Blade = 2
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. BladeNode = 2, Blade = 2
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. BladeNode = 3, Blade = 2
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. BladeNode = 4, Blade = 2
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. BladeNode = 1, Blade = 3
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. BladeNode = 2, Blade = 3
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. BladeNode = 3, Blade = 3
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. BladeNode = 4, Blade = 3

Running InflowWind (v3.03.00, 26-Jul-2016).
Opening InflowWind input file:
E:/softwares/Project/FAST/folder/5MW_Baseline/NRELOffshrBsline5MW_InflowWind_12mps.dat

Reading a 31x31 grid (145 m wide, 17.5 m to 162.5 m above ground) with a characteristic wind
speed of 11.4 m/s. This full-field file was generated by TurbSim (v1.06.00, 21-Sep-2012) on
18-Mar-2020 at 11:57:37.

Processed 12855 time steps of 20-Hz full-field data (642.7 seconds).

Running ServoDyn (v1.06.00a-bjj, 26-Jul-2016).

Running ServoDyn Interface for Bladed Controllers (using Intel Visual Fortran for Windows,
14-Oct-2015).

Running HydroDyn (v2.05.01, 27-Jul-2016).
Generating incident wave kinematics and current time history.
Calculating second order difference frequency wave kinematics.
Calculating second order sum frequency wave kinematics.

Running SubDyn (v1.03.00, 11-Apr-2016).
Calculating Internal Modal Eigenvectors
Timestep: 0 of 630 seconds.

FAST_Solution0:CalcOutputs_And_SolveForInputs:SolveOption2:SrvD_CalcOutput:Running 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.

Warning: Turning off Unsteady Aerodynamics due to high angle-of-attack. BladeNode = 5, Blade = 1

FAST_Solution:FAST_AdvanceStates:AD_UpdateStates:BEMT_UpdateStates(node 5, blade
1):BEMT_UnCoupledSolve:DeterminePhiBounds:There is no valid value of phi for these operating
conditions! Vx = 6.6517, Vy = -37.919, rlocal = 11.743, theta = 0.22769

FAST encountered an error at simulation time 1.50000E-02 of 630 seconds.
Simulation error level: FATAL ERROR

Aborting FAST.


I am not able to understand what are all those warnings. I got these warnings and error even after I adjusted the blade pitch angle according to my mean wind speed ( 0 degree for 11.4 m/s). How can I rectify these warnings and error.

Thank you.

Jason.Jonkman
Posts: 4777
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Jason.Jonkman » Wed Mar 18, 2020 8:50 am

Dear Dhaneesh,

The error regarding "no valid value of phi" has been discussed several times on this forum. In summary, upgrading from AeroDyn v15.03 in FAST 8.16 to AeroDyn v15.04 or upgrading from FAST v8.16 to OpenFAST will solve the problem.

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

Dhaneesh.Machavarapu
Posts: 41
Joined: Sat Feb 29, 2020 9:56 am
Organization: NITcalicut
Location: INDIA

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Dhaneesh.Machavarapu » Thu Mar 19, 2020 12:04 pm

sir,

when I was trying to run FAST by using Aerodyn v15.04 FAST was aborting.


**************************************************************************************************
FAST (v8.16.00a-bjj, 27-Jul-2016)

Copyright (C) 2016 National Renewable Energy Laboratory

This program comes with ABSOLUTELY NO WARRANTY. See the "license.txt" file distributed with this
software for details.
**************************************************************************************************

Running FAST (v8.16.00a-bjj, 27-Jul-2016), compiled as a 32-bit application using single
precision
linked with NWTC Subroutine Library (v2.09.00, 23-Jul-2016)

Heading of the FAST input file:
FAST Certification Test #19: NREL 5.0 MW Baseline Wind Turbine with OC3 Monopile RF
Configuration, for use in offshore analysis

Running ElastoDyn (v1.04.00a-bjj, 26-Jul-2016).

Running BeamDyn (v1.01.04, 26-Jul-2016).

Running BeamDyn (v1.01.04, 26-Jul-2016).

Running BeamDyn (v1.01.04, 26-Jul-2016).

Running AeroDyn (v15.03.00, 27-Jul-2016).

FAST_InitializeAll:AD_Init:ReadInputFiles:ReadPrimaryFile:Invalid numerical input for file
"E:/softwares/Project/FAST/folder/5MW_Baseline/NRELOffshrBsline5MW_OC3Monopile_AeroDyn15.dat"
occurred while trying to read AirDens.

FAST encountered an error during module initialization.
Simulation error level: FATAL ERROR

Aborting FAST.

Can I get some help regarding where I am doing wrong?

Jason.Jonkman
Posts: 4777
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Jason.Jonkman » Thu Mar 19, 2020 12:14 pm

Dear Dhaneesh,

From your command window, it says, "Running AeroDyn (v15.03.00, 27-Jul-2016)." So, it looks like you are using AeroDyn v15.03, not AeroDyn v15.04.

Regardless, from the error message, it doesn't look like your AeroDyn input file is formatted properly. As with any input file format problem, I suggest that you use the Echo option from the input file to debug errors in the input-file processing.

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

Dhaneesh.Machavarapu
Posts: 41
Joined: Sat Feb 29, 2020 9:56 am
Organization: NITcalicut
Location: INDIA

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Dhaneesh.Machavarapu » Thu Mar 19, 2020 11:53 pm

Sir,

When you told me to upgrade my input file to aerodyn v15.04. what I did was I copied Aerodyn v15.04 input file and its Airfoils and Aerodyn blade data files from Aerodyn module to my test folder and mentioned its Path in my Test 19 fst file. And I think that was not the correct way. Because the echo file I got was incomplete. I think the reason was I haven't given source code for this version of input file. Is this the reason ?

If not, can I get some help where I was going wrong. I was attaching the echo file which I got when FAST was aborting.
Attachments
New Microsoft Excel Worksheet (3).xlsx
Aerodyn echo file
(8.74 KiB) Downloaded 10 times

Jason.Jonkman
Posts: 4777
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Jason.Jonkman » Fri Mar 20, 2020 7:36 am

Dear Dhaneesh,

Correct, you'll need to recompile FAST with the updated source code for AeroDyn v15.04 before using AeroDyn v15.04-formatted input files. Or you can upgrade from FAST v8.16 to OpenFAST.

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

Felipe.Alcantara
Posts: 6
Joined: Sun Mar 29, 2020 2:07 pm
Organization: Federal University of Rio de Janeiro
Location: Brasil

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Felipe.Alcantara » Mon Mar 30, 2020 7:45 am

Dear sir/madame,

I was having no problem running some analysis with diferent environmental conditions on the 5MW_Baseline offshore monopile wind turbine that i got when i donwloaded the FAST v8.16 files.

However, once i changed the tower and substructure properties, in the ElastoDyn, AeroDyn, SubDyn and HydroDyn files, the simulation started aborting with the following error message: "There is no valid value of phi for these operating conditions! Vx = -0.48585, Vy = 15.936, rlocal = 11.744, theta = 0.23227"

Therefore, after reading some of the questions in this forum, i decided to update from FAST v8.16 to OpenFAST, because then i would be able to use the Aerodyn 15.04, what could fix this issue. The problem is that, even after the upgrade, the simulation continued aborting, even though Vx wasn't negative. The error messages i've been receiving for diffente blades and blade nodes are the following:

"Warning: Turning off Unsteady Aerodynamics due to high angle-of-attack. BladeNode = 10, Blade = 1"

"BEMT_UpdateStates(node 7, blade 2):BEMT_UnCoupledSolve:There is no valid value of phi for these operating conditions: Vx = 0.71932, Vy = -35.142, rlocal = 19.941, theta = 0.17731, geometric phi = 3.1211
BEMT_UpdateStates(node 8, blade 2):BEMT_UnCoupledSolve:There is no valid value of phi for these operating conditions: Vx = 1.682, Vy = -27.2, rlocal = 24.039, theta = 0.15718, geometric phi = 3.0798"

I think the problem is somehow related to big deflections of the blades, but i don't understand why i started having this problem after i changed the tower and substructure properties and i don't know how to fix it.

Jason.Jonkman
Posts: 4777
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Jason.Jonkman » Mon Mar 30, 2020 7:59 am

Dear Felipe,

After upgrading to AeroDyn v15.04 or newer, you may still get a warning about "no valid value of phi", but this will not trigger an abort. The warning should say, "This warning will not be repeated though the condition may persist" and the simulation should continue. Are you sure you are using OpenFAST?

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

Felipe.Alcantara
Posts: 6
Joined: Sun Mar 29, 2020 2:07 pm
Organization: Federal University of Rio de Janeiro
Location: Brasil

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Felipe.Alcantara » Mon Mar 30, 2020 8:12 am

Dear Jason,

Thank you for answering so quickly.

Yes, i am pretty sure i am using OpenFAST. In order to upgrade from FAST v8.16 to OpenFAST, i replaced the AeroDyn 15.03 inpute file by the Aerodyn 15.04 input file and ran the .fst file with the OpenFAST_x64.exe.

Is there something else i should have done?

I attached a text file with the messages i received when trying to run this simulation.
Attachments
Error - OpenFAST.txt
(15.06 KiB) Downloaded 11 times
Last edited by Felipe.Alcantara on Mon Mar 30, 2020 10:25 am, edited 1 time in total.

Jason.Jonkman
Posts: 4777
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Jason.Jonkman » Mon Mar 30, 2020 10:23 am

Dear Felipe,

Well, it is hard for me to guess what the problem is; I see many warnings that there is "no valid value of phi" with a large range of conditions and "Turning off Unsteady Aerodynamics due to high angle-of-attack". Regardless, these warnings are not themselves triggering the fatal error in OpenFAST. Unfortunately, the true error message is hidden because the warning messages take up so much space (each write screen line length is limited and the last message ends abruptly with "...rlocal = 28.137, thet"; the actual error message would have happened after these warning messages). My guess is the actual error is that the turbine deflections are so large that an aerodynamic analysis node has left the wind field domain, but this is just a guess. I would suggest plotting other things like rotor speed, blade pitch, blade deflection, and tower deflection to get a better sense of what is happening before the simulation aborts. Simplifying the model by disabling features is likely needed to debug the problem.

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

Felipe.Alcantara
Posts: 6
Joined: Sun Mar 29, 2020 2:07 pm
Organization: Federal University of Rio de Janeiro
Location: Brasil

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Felipe.Alcantara » Mon Mar 30, 2020 11:34 am

Dear Jason,

I followed your advice and turned off the computation of aerodynamic loads.

Then i received the following message:

"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."

Do you know how i can fix this problem?

I said earlier that i started having these problems after i changed the properties of the tower and substructure. Do you think that the structure that was introduced is not stiff enought, resulting in big deflections?

What intrigues me is that i haven't changed the blades structural properties.

Jason.Jonkman
Posts: 4777
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Jason.Jonkman » Mon Mar 30, 2020 12:06 pm

Dear Felipe,

The "large blade deflection" warning has been discussed many times on this forum.

I'm not sure how you changed the tower and substructure properties, but could the structural model have gotten stiffer (higher natural frequencies) with your changes? If so, using a smaller time step would probably solve the problem. Use "Search..." in the upper-right to find similar questions and answers.

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

Felipe.Alcantara
Posts: 6
Joined: Sun Mar 29, 2020 2:07 pm
Organization: Federal University of Rio de Janeiro
Location: Brasil

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Felipe.Alcantara » Mon Mar 30, 2020 3:26 pm

Dear Jason,

I looked at some posts related to "large blade deflection" and i decided to reduce the time step, it worked. I stoped receiving the warnings and the simulation ran normally.

However, I was looking at the YawBrFxp time series and i am not sure if it is how it's supposed to be. There force oscilates a lot, assuming even some negative values sometimes.

My guess is that this is caused by ressoance on the tower structure, but i want your opinion about it.

I attached the YawBrFxp and Wind1VelX time series.

Kind regards.
Attachments
YawBrFxp_Time_Series.PNG
YawBrFxp_Time_Series.PNG (105.68 KiB) Viewed 406 times
Wind1VelX_Time_Series.PNG
Wind1VelX_Time_Series.PNG (40.87 KiB) Viewed 406 times

Jason.Jonkman
Posts: 4777
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Jason.Jonkman » Mon Mar 30, 2020 3:37 pm

Dear Felipe,

I see some strong oscillations, but it is hard for me to say whether this is expected or not. How does this compare to the same simulation ran with the original model where you didn't change the substructure? It would also be useful to plot other outputs (e.g. tower-top deflection and tower-base moment), as well as look at the statistics and power spectra density of the time series.

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

Dhaneesh.Machavarapu
Posts: 41
Joined: Sat Feb 29, 2020 9:56 am
Organization: NITcalicut
Location: INDIA

Re: Turning off Unsteady aerodynamics and no valid value of phi.

Postby Dhaneesh.Machavarapu » Sat Apr 04, 2020 2:32 am

Sir,

Sorry for my late reply. Thank you for your earlier suggestion. As per your earlier suggestion I have upgraded from FASTv8.16 to OPENFAST. But when I was trying to run my 5MW_OC3Mnpl_DLL_WTurb_WavesIrr fst File I was getting these errors.

Microsoft Windows [Version 10.0.18362.720]
(c) 2019 Microsoft Corporation. All rights reserved.

C:\Users\Bhargav>E:\softwares\Project\openfast\offshore\5MW_OC3Mnpl_DLL_WTurb_WavesIrr\OpenFAST_x64.exe E:\softwares\Project\openfast\offshore\5MW_OC3Mnpl_DLL_WTurb_WavesIrr\5MW_OC3Mnpl_DLL_WTurb_WavesIrr.fst

**************************************************************************************************
OpenFAST

Copyright (C) National Renewable Energy Laboratory

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-v1.0.0
Compile Info:
- Architecture: 64 bit
- Precision: single
Execution Info:
- Date: 04/04/2020
- Time: 13:48:16+0530

OpenFAST input file heading:
FAST Certification Test #19: NREL 5.0 MW Baseline Wind Turbine with OC3 Monopile RF
Configuration, for use in offshore analysis

Running ElastoDyn.
Running AeroDyn.

FAST_InitializeAll:AD_Init:ReadInputFiles:ReadPrimaryFile:Invalid logical input for file
"E:/softwares/Project/openfast/offshore/5MW_OC3Mnpl_DLL_WTurb_WavesIrr/NRELOffshrBsline5MW_OC3Mono
pile_AeroDyn15.dat" occurred while trying to read TipLoss.
ReadPrimaryFile:Invalid numerical input for file
"E:/softwares/Project/openfast/offshore/5MW_OC3Mnpl_DLL_WTurb_WavesIrr/NRELOffshrBsline5MW_OC3Mono
pile_AeroDyn15.dat" occurred while trying to read IndToler.
ReadPrimaryFile:Invalid numerical input for file
"E:/softwares/Project/openfast/offshore/5MW_OC3Mnpl_DLL_WTurb_WavesIrr/NRELOffshrBsline5MW_OC3Mono
pile_AeroDyn15.dat" occurred while trying to read MaxIter.

FAST encountered an error during module initialization.
Simulation error level: FATAL ERROR

Aborting OpenFAST.

But I haven't done any changes to Tiploss, IndToler, MaxIter parameters in aerodyn input file. Can I get some help regarding this?


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