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interDymFoam: the sinking ship smiles

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Old   March 1, 2014, 06:29
Default interDymFoam: the sinking ship smiles
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Wouter van der Meer
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Hello All,
I try the floatingObject tutorial for interDyMFoam with OF2.3.x. I changed the weight so the object sinks. I also removed the initial wave from setFields.
I would expect the 10l object to sink at a weight of 10.5 kg but it does not. The weight has to be approx 12.5 kg. (meshsize?) Then it sinks but the mesh gets all contracted under the object and the simulation crashes.

Can any one help me changing the parameters I need.
Attached Images
File Type: png T0W12_5.png (13.1 KB, 36 views)
File Type: png T1_2W12_5.png (37.2 KB, 34 views)
File Type: png T2_4W12_5.png (46.0 KB, 46 views)
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File Type: gz dynamicMeshDict.tar.gz (566 Bytes, 9 views)
File Type: gz part_log.interDymFoam.tar.gz (2.7 KB, 3 views)
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Old   March 1, 2014, 06:36
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Bruno Santos
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Greetings Wouter,

Just to give you a heads-up on past experiences on this tutorial, here's a quote from an old post of mine:
Quote:
Originally Posted by wyldckat View Post
The latest talk I know of this topic is at this thread: The floating object tutorial
You can jump to the post #9 on that thread, if you want a very quick summary.
I have no idea if these issues have been somewhat fixed and/or figured out. Although you might want contact the original poster on the following thread: OpenFOAM Tutorial 3D floatingObject strange jump ? - since he's been going around this tutorial since back in November.

Best regards,
Bruno
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Old   March 1, 2014, 09:02
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Wouter van der Meer
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Hello Wyldckat,

thank you for the quick reply.

I had read the post, but I thought it was about multi processor so I ran in single processor. I could run up to a weight of 12 kg but the box just sank until the top was under water and there it stayed for 12 seconds even with waves. So I concluded that this problem was with the moving mesh not updating in the region where the mesh is contracted and I hoped this was a parameter what I had to change. I do not know what parameter but I will try to find out otherwise I have to find another way to let a object sink.

Best regards
Wouter
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Old   March 1, 2014, 10:17
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Hi Wouter,

I've taken a better look into the 3rd image and that very compressed mesh at the base of the box is very suspicious, specially for Courant related simulations.
Are you able to change the dynamic mesh settings to have a wider distance on the propagation/compression of the cells?

Best regards,
Bruno
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Old   March 1, 2014, 15:49
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Hello wyldckat,

Thanks again for checking. I have no idea (yet) to change the dynamic mesh but I will try to find out.

Best Regards
Wouter
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Old   March 2, 2014, 10:38
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Wouter van der Meer
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Hello All,
I thought to have a remedy for the symptom of contracting cells: mapFields
first change position of object in topoSetDict with the help of sixDoFRigidBodyMotionState in time/uniform but the mapping does not work correctly so I have to find something else.

If anyone knows something else please let me know.
Best regards
Wouter
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Old   March 13, 2014, 18:31
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Wouter van der Meer
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Hello All,

Just an update. I tried to run the same problem in foam-3.0. It looks like it runs all the way but I am not able to look at the results in paraview. I saw in the forum that there was a way using the case.openFoam twice but that did not work either. The object stayed in the same place only the surface moved.

any help is appreciated
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Old   March 23, 2014, 13:24
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Hi Wouter,

Indeed, the "floatingObject" tutorial seems to be broken in FOAM-Extend 3.0. Feel free to report this issue at their bug tracker: http://sourceforge.net/apps/mantisbt/openfoam-extend/

In the meantime, you might want to try out the latest OpenFOAM 2.3.x, because they've made an interesting update to at particular tutorial: https://github.com/OpenFOAM/OpenFOAM...4d6c746a5a1d02 - The tutorial in question is "multiphase/potentialFreeSurfaceFoam/oscillatingBox" and it is, as of that commit, using a new boundary condition they implemented recently in 2.3.x, namely "fixedNormalInletOutletVelocity".

Best regards,
Bruno
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Old   March 23, 2014, 13:57
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Wouter van der Meer
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thank you wyldckat.

I tried that tutorial you mentioned, but I do not think that this helps me. My ultimate goal is to model the lemon pip in a glass of tonic (with or without the gin). This pip sinks after a while and than starts to float again because of the CO2 bubbles attaching themselves to the pip. When the pip reaches the surface the bubbles detaches themselves and the pip sinks again. This is a very ambitious endeavour and will probably take forever. So my first step was to make the pip sink and/or rise. I need to figure out how to attach a bubble and make it grow by diffusion of the CO2. The pip will tumble because the bubble will not always attach in the line of cog so there will be a momentum on the pip. A lot to do and so little knowledge of OpenFoam still.

Thanks again for the support
Best regards
Wouter
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