particle solver control problems

antonio · July 14, 2011, 06:31

Hi all.
I am trying to simulate the deposition of particles in a trapezoidal channel thas has initially "clean water". Besides the deposition of these particles i am interesting to see particles concentration profiles along the water column. In this context, i am using the lagrangian particle tracking approach implemented in cfx. I am adopting the following conditions (the most relevant)

ne-way coupling, normal speed at inlet of 0.01 for the water and particles, i have specified 20000 particles at inlet and a mass flow rate of 0.0109445kg/s-1 and at the bottom i have defined the values of 0.3 and 0.6 for the perpendicular and paralell restitution coefficients respectively (i do not have experimental data for this coefficients). In what concerns the particle solver control settings i have defined the following conditions:max.tracking time=2000 and max.tracking distance=25(the channel has 8 meters of extension). However, at the end of the simulation i am receiving the following message

article fate diagnostics
entered domain=20000;
Exceeded time limit=19995;
Exceeded integration limit=5;

As you can see i do not have a detailed information of how many particles have left the domain, how many are collected at the walls, etc..Can anyone with more experience give me a hint on how to solve these messages of particle diagnostics and to have this detailed information?Regards

ghorrocks · July 14, 2011, 09:13

Looks like the particles are just hanging around and not going anywhere. Are you sure buoyancy is correctly set up? Have you set the gravity vector?

antonio · July 14, 2011, 09:40

Thanks Glenn for your comment.
Regarding your question:yes i have defined it. I am using the following "specifications":
water-continuos fluid;
particles-material particles with density of 2650 kg/m3;
morphology-particles transport solid;
buoyancy model-option buoyant with (0,-9.81,0)m^2/s and
buoyancy density reference = 997 kg/m3.

Any more suggestion?

ghorrocks · July 14, 2011, 20:33

The message is clear - almost all the particles are still hanging around at your 2000s cut off time. I would look at them in the post processor and try to find why they have not done anything. Are they moving but very slowly? Are they moving at all? Do you need to increase the cut off time?

July 14, 2011, 06:31	particle solver control problems	#1
antonio Senior Member Join Date: Jan 2010 Posts: 110 Rep Power: 16	Hi all. I am trying to simulate the deposition of particles in a trapezoidal channel thas has initially "clean water". Besides the deposition of these particles i am interesting to see particles concentration profiles along the water column. In this context, i am using the lagrangian particle tracking approach implemented in cfx. I am adopting the following conditions (the most relevant)ne-way coupling, normal speed at inlet of 0.01 for the water and particles, i have specified 20000 particles at inlet and a mass flow rate of 0.0109445kg/s-1 and at the bottom i have defined the values of 0.3 and 0.6 for the perpendicular and paralell restitution coefficients respectively (i do not have experimental data for this coefficients). In what concerns the particle solver control settings i have defined the following conditions:max.tracking time=2000 and max.tracking distance=25(the channel has 8 meters of extension). However, at the end of the simulation i am receiving the following messagearticle fate diagnostics entered domain=20000; Exceeded time limit=19995; Exceeded integration limit=5; As you can see i do not have a detailed information of how many particles have left the domain, how many are collected at the walls, etc..Can anyone with more experience give me a hint on how to solve these messages of particle diagnostics and to have this detailed information?Regards

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July 14, 2011, 09:13		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Looks like the particles are just hanging around and not going anywhere. Are you sure buoyancy is correctly set up? Have you set the gravity vector?

July 14, 2011, 09:40		#3
antonio Senior Member Join Date: Jan 2010 Posts: 110 Rep Power: 16	Thanks Glenn for your comment. Regarding your question:yes i have defined it. I am using the following "specifications": water-continuos fluid; particles-material particles with density of 2650 kg/m3; morphology-particles transport solid; buoyancy model-option buoyant with (0,-9.81,0)m^2/s and buoyancy density reference = 997 kg/m3. Any more suggestion?

July 14, 2011, 20:33		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	The message is clear - almost all the particles are still hanging around at your 2000s cut off time. I would look at them in the post processor and try to find why they have not done anything. Are they moving but very slowly? Are they moving at all? Do you need to increase the cut off time?