Lay length of Mooring line

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Krishnaveni.Balakrishnan
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Lay length of Mooring line

Postby Krishnaveni.Balakrishnan » Wed Apr 03, 2019 1:20 pm

Hi everyone

I would like to know the lay length of the moorning line from FAST . Could anyone kindly help me in locating it.

Thanks
Krishnaveni

Jason.Jonkman
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Re: Lay length of Mooring line

Postby Jason.Jonkman » Wed Apr 03, 2019 1:36 pm

Hi Krishnaveni,

Which mooring module are you using?

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

Krishnaveni.Balakrishnan
Posts: 3
Joined: Mon Feb 11, 2019 10:31 am
Organization: University of Massachusetts
Location: United States

Re: Lay length of Mooring line

Postby Krishnaveni.Balakrishnan » Wed Apr 03, 2019 4:31 pm

Am using Moordyn , So can I take the node positions and look at the point till z starts picking up . After which resultant of x and y coordinates till that pick up (typically am assuming it as touchdown) , can this give me lay length of an individual line?

Jason.Jonkman
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Re: Lay length of Mooring line

Postby Jason.Jonkman » Wed Apr 03, 2019 5:08 pm

Dear Krishnaveni,

Yes, that makes sense to me. Perhaps Matt Hall--the developer of MoorDyn--will comment further.

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

Matt.Hall
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Re: Lay length of Mooring line

Postby Matt.Hall » Wed Apr 03, 2019 7:07 pm

Hi Krishnaveni,

I agree with Jason that your proposed approach is a good solution.

Because MoorDyn is a lumped-mass model, the calculated touchdown length will change abruptly as a node touches down or lifts off. However, if you have enough nodes (short enough segments) the jumps in touchdown length can be made relatively small.

Best,
Matt

Krishnaveni.Balakrishnan
Posts: 3
Joined: Mon Feb 11, 2019 10:31 am
Organization: University of Massachusetts
Location: United States

Re: Lay length of Mooring line

Postby Krishnaveni.Balakrishnan » Thu Apr 04, 2019 8:36 am

Thank you Jason and Matt, Your guidance helped a lot . I have a general question related to that . Say for a given Spar (say OC3) with three mooring lines. Does the initial lay length at 0 time step should be same or it does vary depending on the discretization of nodes. Kindly throw some light on this..

Jason.Jonkman
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Location: Boulder, CO
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Re: Lay length of Mooring line

Postby Jason.Jonkman » Thu Apr 04, 2019 8:45 am

Dear Krishnaveni,

I'm sorry, but I don't really understand your question. As Matt pointed out, the lay length will converge with an increasing level of discretization.

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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