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Particle tracing in COMSOL 4.2

Hi all!

Does anybody have negative experiences with particle tracing in COMSOL 4.2 (and NOT 4.2a)? Because I do.

COMSOL simply fails to trace small particles in even very simple situations. I placed a particle with a radius of 10 microns with zero initial velocity in a reservoir filled with still water. Gravity and buoyancy forces were present, of course. The density of the particle was higher than that of water so the particle was supposed to settle down on the bottom of the reservoir. Instead, it went straight up as if it was in an anti-gravitational field. And just by increasing its radius above 40 microns (and not changing anything else) I could make the particle sink.

Isn't that crazy? The particle size should only affect the sedimentation speed but not whether the particle sedimentation actually occurs or not.

Is this "bug" still present in version 4.2a? If yes, how could I use COMSOL for reliable particle tracing in microfluidic systems and laminar flows?

Thanks,
Daniel

5 Replies Last Post Nov 11, 2012, 9:34 PM EST
Posted: 6 years ago Dec 5, 2011, 1:02 PM EST

Hi all!

Does anybody have negative experiences with particle tracing in COMSOL 4.2 (and NOT 4.2a)? Because I do.

COMSOL simply fails to trace small particles in even very simple situations. I placed a particle with a radius of 10 microns with zero initial velocity in a reservoir filled with still water. Gravity and buoyancy forces were present, of course. The density of the particle was higher than that of water so the particle was supposed to settle down on the bottom of the reservoir. Instead, it went straight up as if it was in an anti-gravitational field. And just by increasing its radius above 40 microns (and not changing anything else) I could make the particle sink.

Isn't that crazy? The particle size should only affect the sedimentation speed but not whether the particle sedimentation actually occurs or not.

Is this "bug" still present in version 4.2a? If yes, how could I use COMSOL for reliable particle tracing in microfluidic systems and laminar flows?

Thanks,
Daniel



I have the similar problems. Let us know how you solve the problem. Do you know how particle tracing study is different than Post Process Plots?

[QUOTE] Hi all! Does anybody have negative experiences with particle tracing in COMSOL 4.2 (and NOT 4.2a)? Because I do. COMSOL simply fails to trace small particles in even very simple situations. I placed a particle with a radius of 10 microns with zero initial velocity in a reservoir filled with still water. Gravity and buoyancy forces were present, of course. The density of the particle was higher than that of water so the particle was supposed to settle down on the bottom of the reservoir. Instead, it went straight up as if it was in an anti-gravitational field. And just by increasing its radius above 40 microns (and not changing anything else) I could make the particle sink. Isn't that crazy? The particle size should only affect the sedimentation speed but not whether the particle sedimentation actually occurs or not. Is this "bug" still present in version 4.2a? If yes, how could I use COMSOL for reliable particle tracing in microfluidic systems and laminar flows? Thanks, Daniel [/QUOTE] I have the similar problems. Let us know how you solve the problem. Do you know how particle tracing study is different than Post Process Plots?

Danielle Lower
Posted: 6 years ago Dec 5, 2011, 6:50 PM EST
It is my understanding that the particle tracing in 4.2 is just a representation of the flow. Those particles can not have a mass/density or be affected by a force. The particle tracing module (in 4.2a) is an actual physics interface which allows you to model particles with or without mass. If you model the particles with mass you are then able to subject the particles to forces, such as drag and gravity. The only downfall of the particle tracing module in 4.2a is that the module does not support particle-to-particle interaction.

Basically, to model the particles in the way you mention in your post, you will need to upgrade to 4.2a.

Hope that helps.
It is my understanding that the particle tracing in 4.2 is just a representation of the flow. Those particles can not have a mass/density or be affected by a force. The particle tracing module (in 4.2a) is an actual physics interface which allows you to model particles with or without mass. If you model the particles with mass you are then able to subject the particles to forces, such as drag and gravity. The only downfall of the particle tracing module in 4.2a is that the module does not support particle-to-particle interaction. Basically, to model the particles in the way you mention in your post, you will need to upgrade to 4.2a. Hope that helps.

Posted: 6 years ago Dec 7, 2011, 3:11 PM EST
Thanks Danielle..


There is an option for particle tracing with mass that considers the mass and the diameter of the particle within drag force.
But if you decrease the particle mass , particles tend to go straight which should not be right.This was reported by some other users on the forum.

I upgraded to 4.2a. I am using particle trajectory study..But trajectory lines still goes thru post walls in the the channel. But at lease they are not straight right now.
Thanks Danielle.. There is an option for particle tracing with mass that considers the mass and the diameter of the particle within drag force. But if you decrease the particle mass , particles tend to go straight which should not be right.This was reported by some other users on the forum. I upgraded to 4.2a. I am using particle trajectory study..But trajectory lines still goes thru post walls in the the channel. But at lease they are not straight right now.

Posted: 6 years ago Jan 31, 2012, 5:50 PM EST
I noticed that with particle tracing I am able to visualize particles moving along the stream lines. However, using the module in 4.2a - I can only plot a velocity field in a single direction.

I have not been able to create a nice visualization of the velocity with particle trajectories. Have you had any luck?
I noticed that with particle tracing I am able to visualize particles moving along the stream lines. However, using the module in 4.2a - I can only plot a velocity field in a single direction. I have not been able to create a nice visualization of the velocity with particle trajectories. Have you had any luck?

Posted: 5 years ago Nov 11, 2012, 9:34 PM EST
Dear All
I am new on comsol, i want to see the effect of electric field on small particle. I mean particle tracing in AC field, but i have no idea how to do that? can anybody help me that how will i apply the field and also please let me know that whether i should do fluidic study or AC/DC study?
Regards
Abid
Dear All I am new on comsol, i want to see the effect of electric field on small particle. I mean particle tracing in AC field, but i have no idea how to do that? can anybody help me that how will i apply the field and also please let me know that whether i should do fluidic study or AC/DC study? Regards Abid

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