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May 26, 2012, 23:19 |
DFBI for very high rotation?
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#1 |
New Member
muhsin
Join Date: Jun 2011
Posts: 9
Rep Power: 15 |
Hi All
I have some difficulties in simulating rolling motion of a small barge in wave flume... -- I am using fine mesh near free surface and body but since DFBI rotation and translation treats whole volume mesh as rigid body, after some time the free surface moves to coarse mesh region and gets distorted and looks like the free surface submerges the body. -- I am able to get comparable results for angles > 10 degrees. but for higher angles like 25 or 30 degrees I am facing the above problem. -- Can anyone suggest what other DFBI models can be used to accommodate for larger DFBI rotation angles for better results. boundary conditions are same as for Boat in head sea tutorial. thank you muhsin |
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May 27, 2012, 04:58 |
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#2 |
Senior Member
Join Date: Oct 2009
Location: Germany
Posts: 636
Rep Power: 22 |
DFBI morphing should be capable of doing it, but morphing usually needs a lot of power and resources. Of course, depending on the mesh size, but the same mesh size needs more resources than the rotation and translation model. And further, you have to make sure, cells don't get too distorted, otherwise you need to remesh, adding additional overhead.
When you're using 7.02, you can use overset meshes, that would be my first choice. But you will need a fine mesh in the whole overlapping area, due to compatibility in cell sizes when the boat rolls, so most likely your mesh will not be smaller due to use of overset meshes.
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May 28, 2012, 15:12 |
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#3 |
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Ryan Coe
Join Date: Jun 2010
Location: Albuquerque, NM
Posts: 98
Rep Power: 16 |
Not sure if it's been published in a paper, but this looks like a similar study that might be useful
http://www.outreach.psu.edu/programs...erson-eric.pdf
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Ryan |
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May 29, 2012, 06:05 |
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#4 |
New Member
muhsin
Join Date: Jun 2011
Posts: 9
Rep Power: 15 |
Thank you Abdul and Ryan. im trying to use morphing it seems to be working.
also the residuals seem to much better than DFBI rot n trans. lets see for larger roll hw it behaves. Ryan i will also have a look into the link sent. |
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March 7, 2014, 06:51 |
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#5 |
Member
Arun Krishnan.L.H
Join Date: Jan 2013
Posts: 75
Rep Power: 13 |
Dear Munshin,
Can you please re-post the link? It is not working now. I am having a problem with DFBI+morphing. Thanks Regards Arun |
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November 10, 2015, 08:00 |
DFBI Morphing with Roll motion
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#6 |
New Member
Join Date: May 2015
Posts: 13
Rep Power: 11 |
Dear Munshin and abdul099
I also use DFBI Morphing to simulate the roll motion and heave motion in the same time, however, when I chose free motion → roll motion and heave motion and monitor them, I found that there was only heave motion, but no any roll motion (no rotation angle was detected). What was wrong with my case? Thanks Su |
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November 10, 2015, 09:53 |
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#7 |
New Member
muhsin
Join Date: Jun 2011
Posts: 9
Rep Power: 15 |
Dear Su,
Please check if you are monitoring properly. If the roll angle is zero all the the time,then do this >>>>>> The roll what you have set is about what axis? X-axis probably... so in your monitors please check that axis correctly. I hope this would help. |
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November 10, 2015, 10:15 |
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#8 |
New Member
Join Date: May 2015
Posts: 13
Rep Power: 11 |
Dear Muhsin
I checked nearly everything that I know and everything I can control, and there was no error with my settings. As you can see from the images attached. The zero degree of rotation angle still confuse me. Best wishes Su |
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November 10, 2015, 10:42 |
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#9 |
New Member
muhsin
Join Date: Jun 2011
Posts: 9
Rep Power: 15 |
Dear Su,
I mean this axis in reports... hope you understand. see the image below: Last edited by muhsin; November 10, 2015 at 13:20. |
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November 10, 2015, 13:00 |
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#10 |
New Member
Join Date: May 2015
Posts: 13
Rep Power: 11 |
Dear Muhsin
Can you upload your picture again? And there is no need to define the axis in the report, cus I can use 6Dof rotation angle report directly from REPORT Tree, and generate the plot. Su |
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