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Emergency stop in floating body simulation

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Old   July 26, 2021, 12:06
Default Emergency stop in floating body simulation
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Xing Lv
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Hi Team REEF3D,

During the simulation, I found that if X 13 chooses 2, it seems that when the ratio of the floating body length to height is not less than 2, the force and velocity of the model will produce huge fluctuations. The simulation process will end with Emergency stop --velocity exceeding critical value N 61. If X 13 0 is used, the model will gradually sink until it is outside the computing area. In addition, with Emergency stop -- velocity exceeding critical value N 61, I tried to turn off wave generation and carried out simulation only in the static tank, the error still rush out. So I want to know what's wrong with the settings, and to be clear, floating body is less dense than water.

Thanks in advance,
Best regards
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File Type: txt ctrl.txt (536 Bytes, 9 views)
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Old   August 3, 2021, 04:39
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Arun Kamath
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I have recently noticed a bug in the grid stretching strategy 11.
Could you please try defining the grid with a different strategy, eg 9 and let me know?

Thanks
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Old   August 4, 2021, 06:02
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Hi Arun,
I tried to generate the grid using other methods in DIVEMesh until I gave up stretching the grid and defined uniform cells throughout the simulation domain, but the problem was not solved and the error message remained.
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Old   August 4, 2021, 09:06
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Arun Kamath
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Are you sure you are running the latest version?
I cannot reproduce the error with the input files you have uploaded, using regular mesh.
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Old   August 5, 2021, 12:52
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Hi Arun,
Thank you for your reply. I have updated the program to the latest version. This example runs successfully using the regular mesh.

I noticed that spurious oscillations may occur in the hydrodynamic force when calculating the movement of a wider floating platform. This is fatal to the simulation process. Is there a better solution?

Attachment will simulate the movement of the floating platform in the numerical wave tank. It cannot run normally unless the translation through z-direction and the rotation around y-direction are prohibited.

Thanks again for your guidance,
Best regards
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File Type: txt ctrl.txt (525 Bytes, 3 views)
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Old   August 9, 2021, 06:02
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Tobias Martin
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Hi,


You can try using sub-iterations in the floating algorithm as this stabilises the simulation. The adjusted control files are attached. Let me know if you need further help.




Kind regards,
Tobias
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File Type: txt ctrl.txt (403 Bytes, 12 views)
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Old   August 25, 2021, 12:01
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Hi Tobias,

Thanks for your guidance. This model ran successfully and got reasonable results.

The detailed explanation of the Y2 and Y3 parameters is not found in the user guide.

How can I get instructions for the latest version?
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Old   August 30, 2021, 04:59
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Y options are developer options which are currently not fully supported in the main release. They will be added to the manual once they are stable.
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Old   September 1, 2021, 12:31
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Thanks for your guidance so far. I am getting more and more proficient in the simulation of 6DOF floating body, and I am looking forward to the richer functions of REEF3D.
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