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interTrackFoam and axisymmetric computations

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Old   January 10, 2013, 10:59
Default interTrackFoam and axisymmetric computations
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Diego Angeli
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Dear all,

I am experiencing problems in setting up an axisymmetric case with interTrackFoam. It is not very clear how the "centerline" patch he is searching for should be defined, since the makeFaMesh ignores the axis when it is composed by 0 faces.

I know that the solver is used/developed by few and maybe I am the first trying to do an axisymmetric calculation with interTrackFoam, but if anyone has a clue about it, that could be very welcome.

thanks

diego
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Old   January 10, 2013, 11:40
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Sandeep Menon
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This is a little tricky - the center line can't be completely degenerate (i.e. just an edge using makeAxialMesh and 0 faces). This is mainly a limitation of the mesh motion solver.

The workaround is to have the center line that is offset from the axis, with very small faces. This works quite well. The trouble is that you'll have to manually make this mesh in a generator, so makeAxialMesh can't help you there.
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Old   January 14, 2013, 08:00
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Diego Angeli
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Dear Sandeep,

thank you for your reply! hope all is fine at UMass!

I tried as you suggested and actually it worked. Unfortunately, though, it appears that the free surface displacement along surface normals does not work well with wedge conditions, and my case is a sort of free-falling jet with a very steep slope, so I would rather need such a feature.
The analogous 3D 180 case is currently working better (albeit enormously slower...)

cheers

diego
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Old   January 30, 2013, 14:04
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Diego Angeli
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Some more updates, just in case anyone is interested or has any clue about possible pitfalls:

Quote:
Originally Posted by diego_angeli View Post
The analogous 3D 180 case is currently working better (albeit enormously slower...)
..and still very slow it is, so in the meantime I dug out to look for alternative solutions

Quote:
Originally Posted by diego_angeli View Post
it appears that the free surface displacement along surface normals does not work well with 2D wedge conditions
I was not very specific about this and I apologize for this, but what I meant is that, if I activate the normalMotionDir switch, the faMesh solver seems not to recognize the wedge condition itself, but instead moves the free surface points out of the plane of the wedge boundaries. I also forced Uz (my neutral direction in the x-y plane) to zero everywhere, but this does not change much.


I also tried to create a (less cumbersome) 3D 90 sector with symmetryPlane conditions. To do this, I used extrudeMesh from the original x-y face. Hence, there are triangular faces on the free surface, connected to the "axis" line, i.e. intersection of the two symmetry planes.
The calculation starts fine and meaningfully, but then it crashes, due to the fact that the the height of the triangular cells adjacent to the free surface collapses to zero at some point. This could be due either to an uneven point redistribution along the "axis", or to a wrong displacement of the common vertex of the triangular cells.

I am aware that this is very specific stuff, but it's always better to ask than to remain silent...
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