Loads extrapolation

[Jacob.Killerup]

Hi Everybody.

I am analyzing the NREL 5MW onshore wind turbine and want to find the loads for 1-year and 50-year recurrence in the DLC 1.1 as stated in IEC61400-1 (p. 35). I have read that one approach is to make a number of bins between the cut-in and cut-out wind speeds of the wind turbine (e.g. 2-m/s). Then it is necessary to run TurbSIM at least 15 times with different rand seeds for each bin and generate 15 separate 10 minute time series. After that the peaks of each 10 minute time series should be determined and an extrapolation can be done by applying a "3 parameter Weibull distribution function".

Does anyone have hands-on experience with this with the output files generated by FAST or can you guide me towards relevant literature or software, which can be used?

Thanks in advance

Best regards
Jacob K. Pedersen
University of Southern Denmark

[Neelabh.Gupta]

Hello Everyone,

I see this post has not been answered. I am curious if there are any NREL post-processing routines (or any other option) that can be used for FAST (ultimate) loads output and comply with IEC61400-1 ed.3. This would include:
- Extrapolation of DLC 1.1 as Jacob mentioned
- Determining characteristic value of ultimate loads (pg. 42)

When turbulent inflow is used, the mean value among the worst case computed loads for different 10-min stochastic realisations shall be taken, except for DLC 2.1, 2.2 and 5.1, where the characteristic value of the load shall be the mean value of the largest half of the maximum loads.

Any insights on these post-processing direction would be greatly helpful.

Best Regards,
Neelabh

[Jason.Jonkman]

Dear Neelabh,

MExtremes can be used to post-process ultimate loads for extreme events: https://nwtc.nrel.gov/MExtremes. MExtremes includes logic to select the mean value of the largest half of the maximum loads. However, while NREL has done a lot of research in loads extrapolation of DLC 1.1, NREL has not included this capability directly within MExtremes (or MCrunch) or otherwise released a public post-processor with this capability.

Best regards,

[Satish.Jawalageri]

Dear Jason,

I am getting following error when I run the MExtremes in matlab. I have attached the input file.

Code: Select all

Error using repmat
Replication factors must be a row vector of integers or integer scalars.

Error in ParseEESettingsFile (line 619)
      Fmt = [ '%*q %*f', repmat( ' %f', 1, NumChans ), ' %f' ];   % No commas allowed in channel list!

Error in MExtremes (line 38)
   [Settings, FileInfo, EEvTable, EEvChart, errStat, errMsg] = ParseEESettingsFile(SettingsFile);

Error in mextremes_certification_tests (line 33)
MExtremes( 'Test_01.mext' );

Thanks,
Satish J

[Jason.Jonkman]

Dear Satish,

I believe the error is that you've set NumEETables = 3 in your input file, but only included 1 row in the table.

Best regards,

[Satish.Jawalageri]

Dear Jason,

Thanks for your reply.

It is working, thanks! I am getting following error when run the tests in the cert folder.

Code: Select all

=======
Test_03
=======

  Running MExtremes (v1.01.00a-gjh, 20-Oct-2015)

  Reading ".\Data\DLC2.3_1.out" (1.409390 MB).
    Rows=1201, Cols=133
  Done
  Reading ".\Data\DLC2.3_2.out" (1.676676 MB).
    Rows=1201, Cols=133
  Done
  Reading ".\Data\DLC2.3_3.out" (1.676676 MB).
    Rows=1201, Cols=133
  Done
Error using figure
Argument must be a Figure object or a positive integer.

Error in plot_load_cases_maximums (line 14)
hfig  = figure(44000 + iPlot);

Error in GenerateCharts (line 39)
            plot_load_cases_maximums(outputFileRoot, iChart, Settings.PlotFormat, EEvChart(iChart).absMax(goodDLCs,:), {FileInfo.DLCs(goodDLCs).DLC_Name},
            FileInfo.ChanNames(EEvChart(iChart).Chans)', EEvChart(iChart).Name, EEvChart(iChart).YLabel);

Error in MExtremes (line 114)
         GenerateCharts(outputFileRoot, Settings, FileInfo, EEvChart, ChanMinAssocValues, ChanMaxAssocValues);

Error in mextremes_certification_tests (line 42)
MExtremes( 'Test_03.mext' );

Thanks,
Satish J

[Jason.Jonkman]

Dear Satish,

I'm not sure, perhaps MATLAB has changed since MExtremes was first written. Can you debug and solve the problem?

Best regards,

[Satish.Jawalageri]

Dear Jason,

Thanks for your reply.

I will try it and let you know if anything comes up.

Thanks,
Satish J

[Vishal.Sairam]

Hi everybody,

I was looking into load extrapolation of DLC1.1 to Vref and I found this thread. I would greatly appreciate it if someone has literature/documentation on how to proceed down this path that you can share with me.

Many thanks in advance!

Best regards,
Vishal

[Jason.Jonkman]

Hi Vishal,

I asked Pat Moriarty of NREL and this was his response:

Start here
https://www.nrel.gov/docs/fy05osti/34421.pdf

and some other good refs are...
https://gcc02.safelinks.protection.outl ... reserved=0
https://gcc02.safelinks.protection.outl ... reserved=0
https://gcc02.safelinks.protection.outl ... reserved=0
https://gcc02.safelinks.protection.outl ... reserved=0
https://gcc02.safelinks.protection.outl ... reserved=0

cheers,
Pat

Best regards,

[Vishal.Sairam]

Hi Jason,

Thank you for your and Pat's replies!

Best regards,
Vishal

[Satish.Jawalageri]

Dear Jason,

Could I please know are there any maximum ULS loads (Force/Bending moment) at mudline (as per IEC load cases) for Task OC3 monopile project in order to design the pile below the mudline.

Thanks,
Satish J

[Jason.Jonkman]

Dear Satish,

Sorry, but I'm not aware that an IEC-based loads analysis has been performed on the NREL 5-MW baseline turbine atop the OC3-monopoile.

Best regards,