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Old   August 20, 2018, 04:53
Default streamlines
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Hello all,

I am having problems to understand physically the result of one simulation. It is a 3D multiphase-jet. I have projected the streamlines in the interface separating the fluids. I have got some streamlines which cross each other (please see attached image). I know that the streamlines cannot cross except where the velocity is zero.

The only reason that I may find to explain this behaviour is that in a 2D projection of a 3D flow, the streamlines may appear to cross.

What do you think?

Thanks in advance
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File Type: jpg Screen Shot 2018-08-17 at 18.00.23.jpg (130.3 KB, 11 views)
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Old   August 20, 2018, 05:15
Philipp Wiedemer
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But were do they cross?
They just seem to converge to a singular point / line in the middle. There the tangential velocity in plane is probably in fact zero with the fluid flowing orthogonal to your plane.

To understand the physics further you could visualize:
- 3D-streamlines
- streamlines in other planes orthogonal to your current one
- streamlines in other planes parallel to your current one
- the tangential velocity in your current plane (to verify my statement)
- a combination of some of them

If they're really just 3D-streamlines projected on your plane then they sure can cross each other, like you said. But it looks too "tidy" to me to be projected, seems more like streamlines calculated by the tangential velocity.
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Old   August 20, 2018, 06:00
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Hello Philipp Wiedemer

Thanks for your replay. I will visualise the different aspects that you have proposed. I will let you know about what I find. Thanks a lot again.
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cfd analysis, streamlines

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