Cyclone analysis

mkal · March 2, 2018, 08:12

yes i meant to say that. But where is the 'trap, escaping, reflecting' boundary condition set. Is there any tutorial you can recommend? Thank you . My English is a little bad.

ghorrocks · March 2, 2018, 19:23

On wall boundary conditions you can set what particles do. By default the coefficient of resititution is zero so particles stop at walls, but you can give it a coefficient of restitution if you want particles to bounce. But it sounds like the default condition will act as the "trap" you describe.

mkal · March 3, 2018, 11:55

Thank you very much ghorrocks. I will set the parallel and vertical coefficients to zero to trap when the particles enter a dustbin wall boundary. I adjust the parallel and vertical coefficient to 1 on the cyclone side wall and the vortex finder wall. Did I understand you correctly? Would you please confirm?
How can I learn the number of pieces falling into an escape and a trap? Please help me.

Gert-Jan · March 5, 2018, 05:56

If you set them equal to 1, then the particles will bounce from the walls until they find an outlet. Probably, most won't find an outlet and will rotate until they hit the limit in distance, time or integration limit, depending on what you set. So separation efficiency of the cyclone will be low.

If you set them equal to 0, the particles will esacpe from the simulation immediately if they hit a wall. So you will have a very high cyclone efficiency.

The reality will be somewhere in between. The values depend on material, shape, humidity, particle size (distribution), etc. You can only find the correct settings if you can compare if with experiments. I told you, that CFD on a cyclone can be a real pain in the "...".

Good luck, Gert-Jan

mkal · March 5, 2018, 12:12

Mr. Gert-Jan and Mr. Glenn Horrocks, I would like to thank you for sharing your valuable information. thanks to you guys we learn something. I'll find the right settings by comparing it with the books. Thank you again .

March 2, 2018, 19:23		#22
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,781 Rep Power: 143	On wall boundary conditions you can set what particles do. By default the coefficient of resititution is zero so particles stop at walls, but you can give it a coefficient of restitution if you want particles to bounce. But it sounds like the default condition will act as the "trap" you describe. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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March 2, 2018, 08:12		#21
mkal Member Join Date: Oct 2016 Posts: 31 Rep Power: 9	yes i meant to say that. But where is the 'trap, escaping, reflecting' boundary condition set. Is there any tutorial you can recommend? Thank you . My English is a little bad.

March 3, 2018, 11:55		#23
mkal Member Join Date: Oct 2016 Posts: 31 Rep Power: 9	Thank you very much ghorrocks. I will set the parallel and vertical coefficients to zero to trap when the particles enter a dustbin wall boundary. I adjust the parallel and vertical coefficient to 1 on the cyclone side wall and the vortex finder wall. Did I understand you correctly? Would you please confirm? How can I learn the number of pieces falling into an escape and a trap? Please help me.

March 5, 2018, 05:56		#24
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,854 Rep Power: 27	If you set them equal to 1, then the particles will bounce from the walls until they find an outlet. Probably, most won't find an outlet and will rotate until they hit the limit in distance, time or integration limit, depending on what you set. So separation efficiency of the cyclone will be low. If you set them equal to 0, the particles will esacpe from the simulation immediately if they hit a wall. So you will have a very high cyclone efficiency. The reality will be somewhere in between. The values depend on material, shape, humidity, particle size (distribution), etc. You can only find the correct settings if you can compare if with experiments. I told you, that CFD on a cyclone can be a real pain in the "...". Good luck, Gert-Jan

March 5, 2018, 12:12		#25
mkal Member Join Date: Oct 2016 Posts: 31 Rep Power: 9	Mr. Gert-Jan and Mr. Glenn Horrocks, I would like to thank you for sharing your valuable information. thanks to you guys we learn something. I'll find the right settings by comparing it with the books. Thank you again .