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A strange phenomenon--the ship passing by the side-by-side piers

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Old   August 17, 2022, 23:34
Question A strange phenomenon--the ship passing by the side-by-side piers
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zhangzhang
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Hi Reef3d Team,

Thank you for reading my post.

A strange phenomenon occurred in the process of simulating the ship passing by the side-by-side piers.

In the ship motion file, it is set that the ship starts to move at 80s, but the result shows that the ship starts to spin at 35s, and the high-speed flow around the hull causes the flow field to become unstable.

The attachment contains control file, ctrl file, stl file and motion file. I really hope to get your help.

Thanks in advance.

Kind regards
Linxi
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Last edited by XXXIMMY; August 17, 2022 at 23:44. Reason: the attachment has been forgotten
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Old   August 18, 2022, 03:29
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Arun Kamath
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Could be an issue with forced motion input.
Will have a look and get back to you
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Old   August 28, 2022, 10:31
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Thank you so much for your response!

I am looking forward to hearing from you very much. Did you have the same problem during the simulation? Your further reply will push my research further and I would appreciate it.

Best Wishes

linxi
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Old   August 30, 2022, 08:03
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Ahmet Soydan
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Hi Linxi,

Could you share the input files you used for your simulation? I guess the input files you shared are not the correct ones since there is something wrong with the files and they can not be run.
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Old   August 30, 2022, 08:47
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Hi soydana,

Thanks a lot for your advice, I reattached my control file, ctrl file, stl file and motion file(The two attachments represent two different conditions, but have the same problem).Thanks for your help.

Also I guess it may be because of version problems that you can't run(I am using version 18.12 and the simulation can be run and finished).

Thanks again, please keep in touch with me if you have any questions.

Best Wishes!

linxi
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Old   August 30, 2022, 11:24
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Ahmet Soydan
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Can you change your motionfile_vec.dat file as below and run the simulation again?

0 0
80 0
150 140
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Old   August 31, 2022, 10:47
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Hi,

I took your suggestion and ran the simulation again, and found that the same problem (the ship circled in place) appeared in the 35s, and the result shown in the attachment appeared in the 70s.

Do you have any better suggestions? I will be very grateful!

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Old   September 1, 2022, 04:38
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1- First and foremost I would suggest using the newest code since the version you use is too old and not supported.

2-You chose prescribed degrees of freedom for surge, sway, roll and pitch motion but they are not prescribed in the ctrl.txt file. On the other hand, you are solving the heave and yaw motions (that is why the ship spins I guess) but I assume that you actually want to solve the heave and pitch motions and to keep the other motions fixed. If I'm right, you can adjust the degrees of freedom as below:

X 11 0 0 1 0 1 0

3-And keep in mind that you may need to change something in your control files for the newest code.

I attached the control files adjusted for the newest code and they can be useful for you.

controlFiles.zip
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Old   September 1, 2022, 09:05
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I am greatly inspired by your suggestion.

I originally wanted to study the transverse drift distance and the yaw moment of the ship separately, so should I set the degree of freedom for the drift study to X 11 0 1 0 0 0 1 , and the degree of freedom for the yaw moment study to X 11 0 0 0 0 0 1 ?

In addition, I will download the latest version as soon as possible to simulate, thank you again for your help !
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