Error: FF wind array was exhausted

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Christian.Tutiven
Posts: 3
Joined: Wed Jul 29, 2015 5:56 am
Organization: Universidad Politécnica de Cataluña
Location: España

Error: FF wind array was exhausted

Postby Christian.Tutiven » Wed Jan 13, 2016 11:51 am

With FAST version 8, usin the turbine model (test_22) "NREL 5.0 MW Baseline Wind Turbine with ITI Barge" when i run the simulation i have this error message:

Error using Run_Baseline (line 35)
Error reported by S-function 'FAST_SFunc' in 'Sta_saludable/FAST Nonlinear Wind Turbine/S-Function':
FAST_Solution:CalcOutputs_And_SolveForInputs:SolveOption2:AD_CalcOutput:IfW_CalcOutput:CalculateOutput:IfW_FFWind:CalcOutput [position=(0, 0, 90)]:
Error: FF wind array was exhausted at 66.062 seconds (trying to access data at 72.104 seconds).

Which can be the reason of this error? Im using the same wind that i use with the test_21 and i never had problems.

Regards,
Christian Tutivèn

Jason.Jonkman
Posts: 4890
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Error: FF wind array was exhausted

Postby Jason.Jonkman » Wed Jan 13, 2016 12:56 pm

Dear Christian,

It looks like you've extended the length of the Test 22 simulation. The FAST CertTest only provides sample input; the wind files in particularly were purposely made very short to reduce the size of the FAST archive. You should run TurbSim to generate the turbulent wind data that you need for your own use: https://nwtc.nrel.gov/TurbSim.

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

Arash.HemmatiTopkanloo
Posts: 47
Joined: Mon Apr 20, 2015 3:35 am
Organization: University of Lisbon
Location: Portugal

Re: Error: FF wind array was exhausted

Postby Arash.HemmatiTopkanloo » Wed Mar 09, 2016 10:13 am

Hi Jason,

I am trying to run FAST for 700 sec and it keeps giving me this error.

FWind_CalcOutput [position=<NaN, NaN, NaN> in wind-file coordinate]:
Error: FF wind array was exhausted at 508.85 seconds (trying to access data at NaN seconds).

I generated wind file with Turbsim for 700 sec (AnalysisTime and UsableTime both 700 sec) and used it in my FAST input but I dont know why it still gives me error?

It is interesting that for PropogationDir =120 degrees it gives error, while for other values of PropogationDir (0 , 30 , 60, 90, 150) it runs without errors.

I am trying to run FAST for different wind directions.

Thank you very much for your invaluable support.

Best Regards,

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

Re: Error: FF wind array was exhausted

Postby Jason.Jonkman » Wed Mar 09, 2016 1:54 pm

Dear Arash,

My guess is that the problem is not with the wind file, but that your model is going numerically unstable for some reason. Are you getting a warning about a "small angle approximation violation" before this error?

Without knowing more about your simulation settings, it's hard to know that what the problem is. Please use "Search..." in the upper right of the forum to search for "unstable" to see how others have solved similar problems in the past.

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

Ryan.Barnhart
Posts: 3
Joined: Tue Nov 29, 2016 11:44 am
Organization: Wetzel Engineering, Inc.
Location: United States - Texas

Re: Error: FF wind array was exhausted

Postby Ryan.Barnhart » Mon Dec 12, 2016 10:34 am

Hi, All -

I wanted to post a similar issue I am having with FF wind array exhausted at a seemingly random time in the simulation. I have triple-checked the grid, and I cannot see how the turbine could violate the grid boundaries. I have also checked several of the output parameters to identify if I'm getting resonance or if the model appears to be going unstable. Unless the instability occurs instantaneously at the time this error is generated, I am not seeing it. I am running FAST8 ElastoDyn only (no BeamDyn). Any insight as to what other things I should be checking to identify the cause of this error? It's occuring about 300s into a 620s sim.

Thanks in advance for your help.

Ryan

Edit: I should also clarify that I am running this using a very basic Simulink model for pitch control/variable speed. This is a parked load case, so pitch is fixed at 90deg and the machine is idling as expected (<1rpm). I also have the following details from the error message that were not given in the above forum post:

SolveOption2:AD14_CalcOutput/Inflow:Inflow:infdist:MATINV:gaussj: Singular matrix encountered
Best Regards,




Ryan Barnhart
Engineering Lead – Materials & Processes
Wetzel Engineering
3914 Gattis School Rd., Suite 103
Round Rock, TX 78664
Office: +1 (512) 989-9194 Ext. 111
Mobile: +1 (913) 484-9329
www.WetzelEngineering.com

Jason.Jonkman
Posts: 4890
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Error: FF wind array was exhausted

Postby Jason.Jonkman » Mon Dec 12, 2016 4:08 pm

Dear Ryan,

If you are confident that the grid is large enough to encompass the rotor under deflection, than the only problem I can think of is numerical instability leading to large deflection. Are you getting the "small angle approximation violation" warning?

You mention that you are modeling an idling rotor, but are receiving an error from AeroDyn v14 subroutine infdist(). However, this subroutine is only used by the generalized-dynamic wake (GDW) model of AeroDyn v14 (DYNIN option). For an idling rotor, it is normally recommend to disable all wake calculations, i.e. set IndModel = NONE, which will disable GDW. Perhaps GDW is driving the model unstable for your case.

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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