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Preprocessing: Gaps and intersections in Geometry

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Old   October 20, 2017, 11:45
Default Preprocessing: Gaps and intersections in Geometry
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Xinxin Zhu
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Hi everybody, I'm quite new to STAR-CCM+. I now have a problem by working with geometry in ANSA which describes an assembly but there exist many intersections and gaps.

It is a CHT problem. I know it's okay by surface wrapper because only the largest internal Volume for the fluid domain is calculated. But the problem lies in the meshing in solid domain.

The intersections and gaps are mostly at the position where two pipes are connected. In reality one of the pipe is pressed into another. The distance between the gap, for example, is 0.45mm and the intersection is about the same depth. Now I'm wondering whether it is OK if I don't fix them in ANSA and directly import into STAR-CCM+.

If I don't fix them, would it cause problems because of the intersection? Would the gap be transformed into an interface where radiation occurs?

If I have to fix them,what is the correct way to do so? Considering that the pipes are steel, should I combine the 2 parts into 1 in ANSA? Or should I duplicate the area where these two are in contact and define one to one part and another to another, so that the 2 pipes remain segregated? If so, how do I guarantee that the mesh of the 2 contacted area are conform?

Thanks a lot

Last edited by Zhudasch; October 22, 2017 at 15:51.
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Old   November 10, 2017, 00:38
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This problem has a lot of answers, all depending deeply on what you have to play with and how badly you want a good answer.

If your parts do not physically touch from a mesh perspective, it is possible to still transfer heat via conduction by using a mapped interface, but your accuracy will suffer. As the distance grows larger (0.45mm is quite large) the mapping gets worse. Radiation might occur if you configure the radiation models correctly.

The best way to fix this is to imprint your solids on to your fluid domain (or vice versa). This will physically distort either domain, but that may be acceptable depending on your needs.

Of course the absolute best way is to fix the CAD, which was obviously drawn incorrectly.
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