model Validation

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Satish.Jawalageri
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Re: model Validation

Postby Satish.Jawalageri » Tue Nov 03, 2020 6:55 am

Dear Jason,

Thanks for your reply.

Could you please share the Test_004 in the standalone HydroDyn CertTest from FAST v8 as I couldn't find the file in which you provided the link below.


Dear Satish,

Not including Wheeler stretching will result in a lower amplitude of wave loading. But Wheeler stretching is known to overpredict the wave loading amplitude anyway. I already suggested the use of WaveMod = 6 in OpenFAST as a way to apply stretching, if needed.

I don't see any reason for you to run FAST v8 since you are already running a newer version--OpenFAST. And downgrading to FAST v8 would require some small input file changes. FAST v8 does not support Wheeler stretching either (but FAST v7 did). Regardless, FAST v8 is available here: https://drive.google.com/drive/folders/ ... sp=sharing.

Best regards,


Thanks,
Satish J

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Re: model Validation

Postby Jason.Jonkman » Tue Nov 03, 2020 6:58 am

Dear Satish,

HD_v2.05.00 in the link below is a self-extracting ZIP archive. Once you extract the files, the Test_004 files should be found in the CertTest directory.

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

Satish.Jawalageri
Posts: 117
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Re: model Validation

Postby Satish.Jawalageri » Tue Nov 03, 2020 9:10 am

Dear Jason,

Thanks for your reply.

Could I know what does ########## indicate in the input files?


Thanks,
Satish J

Jason.Jonkman
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Re: model Validation

Postby Jason.Jonkman » Tue Nov 03, 2020 9:14 am

Dear Satish,

As explained in the HydroDyn documentation, a nonnumeric string in the WaveMod = 6 wave-kinematics files designates that the node is outside of the water at that time step (above the instantaneous water elevation or below the seabed).

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

Satish.Jawalageri
Posts: 117
Joined: Sun May 31, 2020 4:57 am
Organization: University College Dublin
Location: Ireland

Re: model Validation

Postby Satish.Jawalageri » Thu Nov 05, 2020 5:35 am

Dear Jason,

Thanks for your reply.
Could you please suggest me on which software to use to generate all wave kinematics.

Thanks,
Satish J

Jason.Jonkman
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Re: model Validation

Postby Jason.Jonkman » Thu Nov 05, 2020 6:01 am

Dear Satish,

As I mentioned before, NREL has not provided such a software. And we are not in a position to recommend one from elsewhere.

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

Satish.Jawalageri
Posts: 117
Joined: Sun May 31, 2020 4:57 am
Organization: University College Dublin
Location: Ireland

Re: model Validation

Postby Satish.Jawalageri » Thu Nov 05, 2020 10:40 am

Dear Jason,

Thanks for your reply.

1. I have generated wave kinematics externally. I have velocities (x,y,z) and acceleration (x,y,z) at each node at each time step. So my doubt is how do I need to consider these values in .Vxi, .Vyi, .Vzi, .Axi, .Ayi, .Azi as each row represents each time step.

2. Can I consider dynamic pressure file (.DynP) as single column of zero as there is no tapered monopile section (no change in diameter of MP)?

Thanks,
Satish J

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Re: model Validation

Postby Jason.Jonkman » Thu Nov 05, 2020 12:57 pm

Dear Satish,

It sounds like you have all of the data you need (except dynamic pressure). So, all you should need to do is structure the data into the file format readable by HydroDyn. A monopile with no taper would not need the dynamic pressure, so I agree, you can set those to 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

Satish.Jawalageri
Posts: 117
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Organization: University College Dublin
Location: Ireland

Re: model Validation

Postby Satish.Jawalageri » Fri Nov 06, 2020 6:19 am

Dear Jason,

Thanks for your reply.

Regarding the structuring these files, I have considered columns as nodes and rows as time step. Here, in my case I have 41 nodes and total time 60 sec time step of 0.005sec, so 41 columns and 12001 rows. Is that correct way of structuring?

Thanks,
Satish J

Jason.Jonkman
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Re: model Validation

Postby Jason.Jonkman » Fri Nov 06, 2020 8:44 am

Dear Satish,

Yes, that is correct except that there need only be WaveTMax/WaveDT = 12000 rows in your case because no wave kinematics definition is only needed from time = 0 to time = WaveTMax - WaveDT.

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

Satish.Jawalageri
Posts: 117
Joined: Sun May 31, 2020 4:57 am
Organization: University College Dublin
Location: Ireland

Re: model Validation

Postby Satish.Jawalageri » Mon Nov 09, 2020 10:07 am

Dear Jason,

I have included the wheeler stretching (as you mentioned in the previous post), still I am getting the difference in mudline bending moment (attached plot). Could you please advice me on this.

Jason.Jonkman wrote:Dear Satish,

OK, thanks for clarifying.

One big difference I see is that the original OC3 Phase I results for load case 5.1 assumed wave linearity (Airy waves). However, I see that you have enabled second-order wave-kinematics (WvDiffQTF = WvSumQTF = TRUE) in your analysis (hence why your wave elevation is not sinusoidal). The second differences is in regards to wave stretching. The original OC3 Phase I results included Wheeler stretching for the wave kinematics, however, this functionality is not available in the version of OpenFAST that you are running. The lack of Wheeler stretching will impact the wave loads and resulting bending moment at the mudline.

Best regards,



Thanks,
Satish J
Attachments
LC5.1_Task23_Comparison - Copy.jpg
LC5.1_Task23_Comparison - Copy.jpg (48.44 KiB) Viewed 943 times

Jason.Jonkman
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Re: model Validation

Postby Jason.Jonkman » Mon Nov 09, 2020 11:00 am

Dear Satish,

I'm not really sure. How do your wave kinematics compare to those shared with the OC3 Phase 1 data, which are provided on the Google drive linked above?

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

Satish.Jawalageri
Posts: 117
Joined: Sun May 31, 2020 4:57 am
Organization: University College Dublin
Location: Ireland

Re: model Validation

Postby Satish.Jawalageri » Tue Nov 10, 2020 5:37 am

Dear Jason,

Thanks for your reply.

I have attached two plots, 1 - Considered +3m to -20m in hydrodyn and 2 - considered +11m to -20m in hydrodyn.
Wave kinematics are matching with the file in google drive (matches with each time step and node).

1. I am not able to validate, could you please suggest on this.

2. When I change the number of nodes in hydrodyn eventually in wave kinematics (attached figure 1 & 2), the BM values changes but wave height and wave period remains same, could I know where I might be doing wrong in this case?

Dear Satish,

OK, thanks for clarifying.

One big difference I see is that the original OC3 Phase I results for load case 5.1 assumed wave linearity (Airy waves). However, I see that you have enabled second-order wave-kinematics (WvDiffQTF = WvSumQTF = TRUE) in your analysis (hence why your wave elevation is not sinusoidal). The second differences is in regards to wave stretching. The original OC3 Phase I results included Wheeler stretching for the wave kinematics, however, this functionality is not available in the version of OpenFAST that you are running. The lack of Wheeler stretching will impact the wave loads and resulting bending moment at the mudline.

Best regards,


Thanks,
Satish J
Attachments
LC5.1_Task23_Comparison 11 - -20m.jpg
LC5.1_Task23_Comparison 11 - -20m.jpg (46.56 KiB) Viewed 932 times
LC5.1_Task23_Comparison 3 - -20m.jpg
LC5.1_Task23_Comparison 3 - -20m.jpg (47.94 KiB) Viewed 932 times

Jason.Jonkman
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Location: Boulder, CO
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Re: model Validation

Postby Jason.Jonkman » Tue Nov 10, 2020 6:25 am

Dear Satish,

Have you run the model long enough to ensure all start-up transients have died out? The OC3 Phase 1 results on Google drive are provided after all start-up transients die out.

And I don't really understand your question about the wave height and period. You are using WaveMod = 6, correct? The wave height and period should be as you specified.

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

Satish.Jawalageri
Posts: 117
Joined: Sun May 31, 2020 4:57 am
Organization: University College Dublin
Location: Ireland

Re: model Validation

Postby Satish.Jawalageri » Tue Nov 10, 2020 7:26 am

Dear Jason,

Thanks for your reply.

- Yes I did consider TStart as 30 sec.

- What I mean is when I change the number of nodes, I am getting different values of BM.

- I can see values in dynamic pressure column in wave data of google drive file, but you suggested to set it to zeroes unless it is tapered section.

Thanks,
Satish J


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