Question about using TMD in nacelle

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Xing.Wei
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Question about using TMD in nacelle

Postby Xing.Wei » Mon Jan 07, 2019 9:20 am

Dear All

I am using FAST 8 and encountered a problem with TMD in the nacelle. I was trying to use the nacelle TMD but there is always an error. So, I decided to do a very simple test by using the "test01.fst" provided by FAST 8 and enabling the use of nacelle TMD. I copied the file "NRELOffshrBsline5MW_ServoDyn_TMD.dat" to the folder "AWT27" where other files of "test01.fst" are placed. I set "CompNTMD" to be True in the file "Test01_ServoDyn.dat" and set "TMD_X_DOF" to be True in "NRELOffshrBsline5MW_ServoDyn_TMD.dat". I think this is the way to enable the use of nacelle TMD in X direction. However, I got the following error when I try to run the Simulink.

question.png
question.png (21.42 KiB) Viewed 2074 times


If I disable the nacelle TMD and enable the tower TMD, it works! This is the part I am really confusing. Sincerely hope someone could tell me the reason.

Best

XING WEI

Jason.Jonkman
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Re: Question about using TMD in nacelle

Postby Jason.Jonkman » Mon Jan 07, 2019 9:45 am

Dear Xing Wei,

Did you change the mass of the TMD in NRELOffshrBsline5MW_ServoDyn_TMD.dat? The TMD mass in that file is 35000 kg, whereas the total rotor-nacelle-assembly (RNA) mass of the AWT27 turbine is only 7216 kg. Normally a TMD mass is about 10% of the RNA mass. My guess is the unphysically large TMD mass is causing your model with TMD to go numerically unstable.

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
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Xing.Wei
Posts: 68
Joined: Mon Jul 18, 2016 1:42 pm
Organization: University of Warwick
Location: University of Warwick, Coventry,UK

Re: Question about using TMD in nacelle

Postby Xing.Wei » Mon Jan 07, 2019 9:58 am

Dear Jason

You are correct! Sorry I did not realize this could be a problem.

Best

XING WEI

Akheel.Kodambiyakamkizhakkakam
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Re: Question about using TMD in nacelle

Postby Akheel.Kodambiyakamkizhakkakam » Sun Nov 15, 2020 8:48 am

Dear Sir,
I am trying to simulate spar with TMD in nacelle. The CompNTMD in 'NRELOffshrBsline5MW_OC3Hywind_ServoDyn' file is set true and the file name is given (all other parameters kept unaltered). In 'NRELOffshrBsline5MW_ServoDyn_TMD' file, the following changes were made(all other kept unaltered):
TMD_Y_DOF = false
TMD_X_DWSP = 4
TMD_X_UWSP = -4
TMD_Y_PLSP = 4
TMD_Y_NLSP = -4
TMD_X_M = 10470
TMD_X_K = 86660
TMD_X_C = 4203

With above modifications, the TTDspFA and PtfmSurge remain unchanged with and without TMD.

Hence I tried to run the 'NRELOffshrBsline5MW_ServoDyn_TMD' file with its default value. Even then the response was unaltered.
1. Can I know where am I making mistakes?
2. Which among TMD_X_DWSP, TMD_X_UWSP, TMD_Y_PLSP, TMD_Y_NLSP sets the stroke limit?

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Re: Question about using TMD in nacelle

Postby Jason.Jonkman » Mon Nov 16, 2020 6:51 am

Dear Akheel,

I don't really see any problems with you TMD settings. Do you see any effect from any output channel when you enable the TMD? One obvious effect I would expect you'd see is the tower-top force should increase due to the extra mass in the nacelle.

The stroke limit (stop position) for X-based TMD is TMD_X_DWSP (downwind) and TMD_X_UPSP (upwind).

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

Akheel.Kodambiyakamkizhakkakam
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Re: Question about using TMD in nacelle

Postby Akheel.Kodambiyakamkizhakkakam » Mon Nov 16, 2020 8:48 am

Dear Sir,
Can I know what exactly did you mean by effect from output channel?

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Re: Question about using TMD in nacelle

Postby Jason.Jonkman » Mon Nov 16, 2020 8:54 am

Dear Akheel,

I meant do any of the OpenFAST outputs change when you enable the TMD? For example, given the nacelle TMD mass of 10470 kg, I would expect the tower-top vertical force (YawBrFzn) to increase by about 103 kN relative to the simulation without the TMD enabled. Do you see that? I would expect this extra mass would also impact the tower deflection, platform heave, etc. a bit.

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

Akheel.Kodambiyakamkizhakkakam
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Re: Question about using TMD in nacelle

Postby Akheel.Kodambiyakamkizhakkakam » Mon Nov 16, 2020 9:30 am

Dear Sir,
I could not find any YawBrFzn in mu output file. Only YawBrFxt YawBrFyt YawBrFzt are there. How to get 'YawBrFzn' in output file?

I need more insight into following aspects
1. How to enable TMD in both nacelle and tower If they have different properties like stop position, stiffness, mass etc..
2. Can the matlab function 'fft' is sufficient to convert response time series to PSD
3. How to validate my results under wind and wave loads (As I am not able to match my results with the paper I have been using

Jason.Jonkman
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Re: Question about using TMD in nacelle

Postby Jason.Jonkman » Mon Nov 16, 2020 9:41 am

Dear Akheel,

"YawBrFxt, YawBrFyt, and YawBrFzt" are not valid outputs from the ElastoDyn module; check again. The complete list of available outputs from OpenFAST is documented here: https://openfast.readthedocs.io/en/mast ... eters.xlsx. Simply add the outputs you want in the OutList section of each module.

Here are my answers to your questions:

1. Setting both CompNTMD and CompTTMD to True will enable both a nacelle and tower TMD. Each TMD should have a corresponding TMD input file.
2. An FFT is not the same as a PSD, although you can derive a PSD via FFT, e.g., as I provided in the MATLAB script Jason_PSD.m in the following forum topic: viewtopic.php?f=4&t=2219&p=12891.
3. I'm not really sure I know enough about what you are asking to comment.

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

Akheel.Kodambiyakamkizhakkakam
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Re: Question about using TMD in nacelle

Postby Akheel.Kodambiyakamkizhakkakam » Mon Nov 16, 2020 10:23 am

Dear Sir,
This message is regarding Q3 of my previous message. What I meant was, I need to learn how to simulate the response of OC3 spar under wind and wave loads. With the input data in the paper (Yang e.al), I did not get the exact response as available in the paper. So Do I need to make changes to any other parameters other than the data provided in the paper (i.e. wind speed, turb intensity, wave height, wave period, reference coordinates is at COG of platform)

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Re: Question about using TMD in nacelle

Postby Jason.Jonkman » Mon Nov 16, 2020 10:35 am

Dear Akheel,

I'm not familiar with the paper you refer to, and so, cannot comment on 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

Akheel.Kodambiyakamkizhakkakam
Posts: 51
Joined: Wed Jul 15, 2020 5:28 am
Organization: NIT Calicut
Location: India

Re: Question about using TMD in nacelle

Postby Akheel.Kodambiyakamkizhakkakam » Mon Nov 16, 2020 8:40 pm

Jason.Jonkman wrote:Dear Akheel,

I meant do any of the OpenFAST outputs change when you enable the TMD? For example, given the nacelle TMD mass of 10470 kg, I would expect the tower-top vertical force (YawBrFzn) to increase by about 103 kN relative to the simulation without the TMD enabled. Do you see that? I would expect this extra mass would also impact the tower deflection, platform heave, etc. a bit.

Best regards,


Yes Sir, YawBrFzn has increased in magnitude. Without TMD this value is around -3450, with TMD it is around -3900 kN.

Jason.Jonkman
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Re: Question about using TMD in nacelle

Postby Jason.Jonkman » Mon Nov 16, 2020 9:07 pm

Dear Akheel,

OK, well at least you are seeing some effect of the TMD on your simulation results, so, you know it is being called correctly.

Best results,
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

Akheel.Kodambiyakamkizhakkakam
Posts: 51
Joined: Wed Jul 15, 2020 5:28 am
Organization: NIT Calicut
Location: India

Re: Question about using TMD in nacelle

Postby Akheel.Kodambiyakamkizhakkakam » Tue Nov 17, 2020 12:19 am

Jason.Jonkman wrote:Dear Akheel,

I'm not familiar with the paper you refer to, and so, cannot comment on that.

Best regards,

Dear Sir,
Since you are not familiar with it, can you suggest some paper so as to compare the responses.

Jason.Jonkman
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Re: Question about using TMD in nacelle

Postby Jason.Jonkman » Tue Nov 17, 2020 6:27 am

Dear Akheel,

I'm sorry, but I'm not sure I understand your question. What do you want to compare and for what purpose?

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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