Solid particles not influenced by airflow

BlauweKaas · January 16, 2014, 09:05

Hi,
I'm having trouble with particle tracking.
The solid particles are not influenced by the fluid they are in (Air at 25c). Even though they are Fully coupled with the air.
The particles only change direction when hitting a wall.
Has anyone seen this before?
Thanks!

BlauweKaas · January 16, 2014, 15:42

To clarify my problem:

The airflow which acts like it should:

And the particles, which just go straight ahead:

ghorrocks · January 16, 2014, 18:08

Could be lots of things.

Are the material properties correct?
Is the interphase drag set correctly?
Is the particle integration time step set correctly?
Is the simulation converged?

BlauweKaas · January 18, 2014, 13:11

I check if they converged, but I was stupid enough to leave the maximum amount of iterations at 100.
After increasing the number, they still don't seem to converge.
Does this per se mean that the particles won't interact with the flow?
This is from the box posted above:

And the butterfly valve tutorial:

ghorrocks · January 19, 2014, 05:54

THis question is an FAQ: http://www.cfd-online.com/Wiki/Ansys...gence_criteria

Don't pay too much attention to the convergence history of the tutorials. They show you how to set a simulation up, but they do not show you how to do an accurate simulation. THe results the tutorials give are not very accurate.

But don't worry about the convergence for now, you have a more fundamental problem if the particles travel in straight lines. The points I raise in my previous post are a starting point in what to check.

January 16, 2014, 09:05	Solid particles not influenced by airflow	#1
BlauweKaas New Member Blauwe Kaas Join Date: Oct 2013 Posts: 3 Rep Power: 13	Hi, I'm having trouble with particle tracking. The solid particles are not influenced by the fluid they are in (Air at 25c). Even though they are Fully coupled with the air. The particles only change direction when hitting a wall. Has anyone seen this before? Thanks!

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January 16, 2014, 15:42		#2
BlauweKaas New Member Blauwe Kaas Join Date: Oct 2013 Posts: 3 Rep Power: 13	To clarify my problem: The airflow which acts like it should: And the particles, which just go straight ahead:

January 16, 2014, 18:08		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Could be lots of things. Are the material properties correct? Is the interphase drag set correctly? Is the particle integration time step set correctly? Is the simulation converged?

January 18, 2014, 13:11		#4
BlauweKaas New Member Blauwe Kaas Join Date: Oct 2013 Posts: 3 Rep Power: 13	I check if they converged, but I was stupid enough to leave the maximum amount of iterations at 100. After increasing the number, they still don't seem to converge. Does this per se mean that the particles won't interact with the flow? This is from the box posted above: And the butterfly valve tutorial:

January 19, 2014, 05:54		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	THis question is an FAQ: http://www.cfd-online.com/Wiki/Ansys...gence_criteria Don't pay too much attention to the convergence history of the tutorials. They show you how to set a simulation up, but they do not show you how to do an accurate simulation. THe results the tutorials give are not very accurate. But don't worry about the convergence for now, you have a more fundamental problem if the particles travel in straight lines. The points I raise in my previous post are a starting point in what to check.