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-   -   Cyclone separator- Full run (http://www.cfd-online.com/Forums/cfx/114548-cyclone-separator-full-run.html)

Magma March 13, 2013 05:48

Cyclone separator- Full run
 
1 Attachment(s)
Hello!!
First thanks to forum members for helping me out with jet ejector!! with your help I could finally simulate multiphase jet ejector problem.


I am working out the cyclone separator with particle tracking. I believe the geometry is OK and the boundary conditions must be ok...
I am facing the problem that the streamlines do not go till the end of geometry. I have tried it with higher relevance(geometry) and higher number of iterations.
I have attached a plot of streamline with the post. Can anyone suggest me what is wrong or what needs to be done?
And I have tried higher velocity at the inlet too.

oj.bulmer March 13, 2013 07:03

Streamlines terminate the moment they hit solid walls. If you observe the definition of streamlines, it is a curve such that tangent at any direction will represent direction of velocity at that point. It may be wrong to interpret them essentially as a path of molecules of the fluid etc, since the fluid will bounce back from the walls, streamlines won't. This is the reason you don't see the streamlines till the bottom hole there.

How about using particle tracks?

Regards
OJ

ghorrocks March 13, 2013 07:06

Have a look at the particle termination parameters. One of them is being triggered causing the particle track to end.

Sorry, just reread your post and it is a streamline you are showing. Then this is just an integration error in the streamline. Try genrating new streamlines from slightly different seed points. Also finer mesh would help.

Magma March 13, 2013 23:21

Cyclone separator-Tracks-streamlines
 
Oj & Ghorrocks!
There are essentially two materials defined: one fluid being air and the next is particle solid(ash, which is for particle track).
I have increased the smoothness of the geometry but the problem is same.
I believe particle tracks depend upon the moment of fluid as it is fully coupled with the fluid.(Fluid behavior effecting the path lines of particle and vice-versa).
So I am ok with the particle track.
As ghorrocks said, there may be problem with integration, which i will see.

Thanks again, I will seek consultation as per need!! :)

Sanyo March 14, 2013 09:28

Dear Magma,

Your solution is perfectly all right. In cyclone separators, there are two vortices. Outer & inner. Flow enters into cylinder from inlet & outer vortex is formed along the walls. Dust separation is minimal in this region. When Flow reaches to cone area, gas changes its direction & start to travel upwards forming second vortex i.e. inner vortex. Dust separation is maximum in cone area due to change in gas flow direction & drop in gas velocity.

If you need to see the streamlines in the cone region, take a plane at middle of cylinder (or maybe start of the cone) & start your streamlines from this plane. Or start the streamlines from particle outlet & define the streamline direction as backward.

Also, you might want to increase the streamline termination length in streamline settings.

Regards,

-Sanyo


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