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Birkov August 25, 2010 03:12

Boat problem
Hi to all,

I would like to ask you if anyone have any experience with solving boat hydrostatics and hydrodynamics in CFX (or Fluent) (any marine engineer?).
I'm curently testing Ansys CFX 12.1 with ICEM.
I have 6DOF boat (5 DOF when moving) with 2 phases (Air, Water). Evertything works relatively fine with small boat movements.
Because CFX has not inner remeshing engine I have to use ICEM for remeshing. Situation with ICEM is better but there are some difficulties.

If anyone have any advise I would be glad.
Second choice for this time is CD-Adapco with STAR-CCM+ (I've already saw some references and it should work).

Thank you very much for your time.


Kindel August 25, 2010 15:35

Hi Berkov,
I wish I could offer some suggestions. I am currently trying to do basically the same thing, using the beta Rigid Body 6dof sover in CFX 12, utilizing ICEM remeshing. I have been fighting with the remeshing for several days now, trying to get it working correctly. My model works fine with small movement of my rigid body, but if I get very much movement my mesh deforms and I get negative element errors. Have you had much success using ICEM remeshing? I am still getting negative elements, even after it remeshes.

Sorry I can't be of any help, but if I have any breakthroughs I'll be sure to let you know! By the way, thanks for posting the link to EDM's remeshing example-it was very helpful.


ghorrocks August 25, 2010 17:46

CFX V13 has full 6 DOF built-in as a release feature. If 6 DOF is of interest to you then I recommend you get the preview version of V13.

Birkov August 26, 2010 00:43

As a ghorrocks said in verison 13 will be full 6DOF. But if you want to solve bigger movements you need ICEM.
But you wrote that you have negative elements with ICEM. If you set up everything right you should not get negative elements. That's why you want to use remeshing. You should check if your rigid body "just" move or if have rotation. For remeshing all 6DOF you need write script for checking rotation of your rigid body. ICEM can remeshing only slide movement by default.
If you use only CFX you need set up mesh stiffness properly.
Another way how to solve it is use another software like STAR-CCM+.


ghorrocks August 26, 2010 06:45

CFX Support has several examples of 6 DOF with ICEM remeshing. If you ask support they should give it to you. This is by far the easiest way to get started.

Birkov August 26, 2010 06:50

If they have it will be great. I just spoke with some peole from Ansys so I will ask them again.
Thank you.


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