AeroDyn Error Code: FF wind array exhausted

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John.Chang
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AeroDyn Error Code: FF wind array exhausted

Postby John.Chang » Thu Aug 29, 2019 8:39 am

Dear ladies and gentlemen,
I am having trouble finding the problem with my simulation. I think, according to the error massage, the problem lies in AeroDyn. However, I can’t figure out what exactly the problem is.
I am trying to simulate DLC on a floating offshore wind turbine (5 MW NREL reference wind turbine for offshore system & semi-submersible floating system for phase II of OC4).
Wind speed: 12 m/s, hub height 100 m

The error code are as followed:
-----------------------------------------------------------------------------------------------------------
INFO: Aerodynamic loads calculated using AeroDyn (v13.00.00a-bjj, 31-Mar-2010).
Heading of the AeroDyn input file: NREL 5.0 MW offshore baseline aerodynamic input properties; Compatible with AeroDyn v13
Assuming E:/LCT – Offshore / 03_example_load_calculation / DLC11 / DLC11_WS0012_WD0000_UF0008_HE0200_TS0007 / mbs_db_aerodyn / AeroDyn_PP / IEC2A_NTM_WS0012_WD0000_UF0008_HE0200_TS0007.wnd is a binary FF wind file.
Reading a 26x26 grid (140 m wide, 30 m to 170 m above ground) with a characteristic wind speed of 12 m/s.
Processed 12634 time steps of 20-Hz full-field data (631.65 seconds).
Error: FF wind array was exhausted at 0 seconds (trying to access data at -3.0427 seconds).
Error getting velocity in AeroDyn/AD_WindVelocityWithDisturbance().
FATAL ERROR in AeroDyn library!

-----------------------------------------------------------------------------------------------------------
For the DLC 1.1 analysis with the wind speed of 3, 6, 9 m/s, the simulation ran without any trouble. However, I am experiencing the same fatal error as above in the simulation with the wind speed 12, 15, 18, 21, 24 m/s.

After going through the forum I assumed, the grid of the find field was the problem. But it did not correct my problem.

Your advice will be highly valued.
Thank you.

Sincerely,

John Chang

Jason.Jonkman
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Re: AeroDyn Error Code: FF wind array exhausted

Postby Jason.Jonkman » Thu Aug 29, 2019 4:43 pm

Dear John,

Do you receive this error right away at time zero? Is your initial surge displacement far downwind, where perhaps there is no wind defined in the simulation?

I'm not sure if you are using TurbSim to generate the turbulent wind data file or not, but you may be interested in the UsableTime = "ALL" option of TurbSim, which ensures that the turbulent wind data generated is periodic, and so, FAST assumes that the wind data extends effectively forever in the along-wind direction. I would not expect you to receive the error you are receiving when using this option.

I also noticed that you are using AeroDyn v13, which presumably means that you are using FAST v7. The floating wind modeling capability has been drastically improved in newer versions of FAST e.g. FAST v8 or OpenFAST. I would suggest upgrading.

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

John.Chang
Posts: 5
Joined: Fri Jul 19, 2019 12:34 am
Organization: self
Location: Germany

Re: AeroDyn Error Code: FF wind array exhausted

Postby John.Chang » Fri Sep 27, 2019 3:09 am

Dear Dr. Jonkman,

thank you for your informative reply.

As you have suggested, i have implemented UsableTime = "ALL" in TurbSim. However, the problem that i had, kept on appearing.
I am running on various wind speed and turbulence seeds.
The error codes that i get are as following:

AERODYN: INFO: Error FF wind array boundaries violated: Grid too small in Y direction. Y=-81.049; Y boundaries = [-75, 75]

AERODYN: INFO: Error: FF wind array was exhausted at 0 seconds (trying to access data at -14.964 seconds).


The codes appear in separate experiments.

For the error code....
AERODYN: INFO: Error FF wind array boundaries violated: Grid too small in Y direction. Y=-81.049; Y boundaries = [-75, 75]
Could increasing the GridHeight and GridWidth in TurbSim be an option to solve the issue?


As for the error code....
AERODYN: INFO: Error: FF wind array was exhausted at 0 seconds (trying to access data at -14.964 seconds).
According to Mr.Marshall.Buhl "the code error means the combination of surge and pitch has pushed one of the blades past the beginning or end of the wind volume."
What if, for example using the above error, I create an "AeroDyn - wind file" that starts from minus valued time to cover the access time.

! Wind file test
! Time Wind Wind Vert. Horiz. Vert. LinV Gust
! Speed Dir Speed Shear Shear Shear Speed
-20 8.13 0.000 0.00 0.000 0.0 0 0
0 8.13 0.000 0.00 0.000 0.0 0 0
100 8.13 30.000 0.00 0.000 0.0 0 0

Thank you.

Sincerely,

John Chang

Jason.Jonkman
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Location: Boulder, CO
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Re: AeroDyn Error Code: FF wind array exhausted

Postby Jason.Jonkman » Fri Sep 27, 2019 9:53 am

Dear John Chang,

Regarding the error, "FF wind array boundaries violated: Grid too small in Y direction...", yes, increasing the GridWidth in TurbSim should solve that problem.

Looking briefly at the source code, I don't see that it is possible to receive the error, "FF wind array was exhausted at..." if you are generating periodic wind data in TurbSim. This error can only be triggered if the FF wind data is not periodic. Neither will this error be triggered when using AeroDyn "hub-height" wind file formats, so, there is no reason to set the first time in those files less than zero.

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

John.Chang
Posts: 5
Joined: Fri Jul 19, 2019 12:34 am
Organization: self
Location: Germany

Re: AeroDyn Error Code: FF wind array exhausted

Postby John.Chang » Mon Sep 30, 2019 10:14 am

Dear Doctor Jonkman,

Thank you once more for the reply.

The error code, "FF wind array boundaries violated: Grid too small in Y direction..." was solved by changing the GridWidth / Height in TurbSim.

However, i am still getting error code "FF wind array was exhausted at...", even though i have implemented UsableTime = "ALL" option of TurbSim.
I have tried both with and without quotation marks.

--------Turbine/Model Specifications-----------------------
26 NumGrid_Z - Vertical grid-point matrix dimension
26 NumGrid_Y - Horizontal grid-point matrix dimension
0.05 TimeStep - Time step [seconds]
600 AnalysisTime - Length of analysis time series [seconds] (
"ALL" UsableTime - Usable length of output time series [seconds]
90.00 HubHt - Hub height [m] (should be > 0.5*GridHeight)
170.00 GridHeight - Grid height [m]
170.00 GridWidth - Grid width [m] (should be >= 2*(RotorRadius+ShaftLength))
0 VFlowAng - Vertical mean flow (uptilt) angle [degrees]
0 HFlowAng - Horizontal mean flow (skew) angle [degrees]

I am analyzing NREL 5 MW reference wind turbine for the offshore system on a floating semisubmersible floating system of OC4.

Sincerely,

John Chang

Jason.Jonkman
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Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
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Re: AeroDyn Error Code: FF wind array exhausted

Postby Jason.Jonkman » Mon Sep 30, 2019 11:22 am

Dear John,

Which version of FAST are you using? From an earlier post, I thought that you were using FAST v7, but FAST v7 could not model a semisubmersible well, so, now I'm not sure.

I'm not sure I understand why you are receiving this the error regarding "FF wind array was exhausted at..." when using UsableTime="ALL". I would suggest running the simulation through the debugger to identify 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

John.Chang
Posts: 5
Joined: Fri Jul 19, 2019 12:34 am
Organization: self
Location: Germany

Re: AeroDyn Error Code: FF wind array exhausted

Postby John.Chang » Fri Oct 04, 2019 6:49 am

Dear Dr. Jonkman,

is there any other way to increase the wind volume for the simulation, other than changing the UsableTime = "ALL" in TurbSim ?

Sincerely,

John Chang

Jason.Jonkman
Posts: 4484
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
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Re: AeroDyn Error Code: FF wind array exhausted

Postby Jason.Jonkman » Fri Oct 04, 2019 7:15 am

Dear John,

I'm still not sure which version of FAST you are using. Older versions of FAST/AeroDyn did not interpret periodic wind data (generated with the UsableTime="ALL" option of TurbSim); this feature was added a few years ago. I would suggest upgrading to FAST v8 or OpenFAST, in which case I would not expect you to receive an error regarding "FF wind array was exhausted at...".

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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