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Streamlines on Walls

Posted Jan 23, 2011, 8:17 p.m. EST 5 Replies

Daniel Hankins
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I am using streamlines to show the flow and displacement of particles in a serpentine microchannel and it works fine when the particles are repelled from the edges and focused into the middle of the channel. But when the particles are attracted to the sides of the channel the stream lines get closer until they touch the boundary and disappear.

The image attached is of what is currently happening, the red streamline represent the flow of microparticles experiencing a positive DEP force and therefore are attracted to the corners of the channel. I want to the streamlines to continue along the channel wall all the way to the end instead of disappearing. Is there any way I can make the streamlines follow the boundary to the end of the channel when they make contact, instead of just disappearing?

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5 Replies Last Post Mar 1, 2011, 3:06 p.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 24, 2011, 1:24 a.m. EST
Hi

these are typically issues I send to "support", I believe its some special limitation (probably unwanted) in the code, but there might be others out there with some better ideas.

Have you tried to play with all the initial conditions for the streamlines ?

--
Good luck
Ivar
Hi these are typically issues I send to "support", I believe its some special limitation (probably unwanted) in the code, but there might be others out there with some better ideas. Have you tried to play with all the initial conditions for the streamlines ? -- Good luck Ivar
Daniel Hankins
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Posted: 1 decade ago Jan 24, 2011, 5:32 p.m. EST
well if it is just an issue, or limitation or whatever, I would certainly like to help and send it to support. But then has anyone got any creative ideas on how to fix it or do it differently?

I have played with the starting coordinates, that is all I know of for initial conditions. but that doesn't change much because as long as the channel is long enough all of the streamlines should eventually reach the wall no matter where they started from.
well if it is just an issue, or limitation or whatever, I would certainly like to help and send it to support. But then has anyone got any creative ideas on how to fix it or do it differently? I have played with the starting coordinates, that is all I know of for initial conditions. but that doesn't change much because as long as the channel is long enough all of the streamlines should eventually reach the wall no matter where they started from.
Kristian Jensen
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Posted: 1 decade ago Jan 25, 2011, 8:14 a.m. EST
If you remove the attraction at some (very small) distance to the wall, the streamlines should never touch the wall. If they still touch and disappear you could make the wall repellant at some (very small) distance.

If believe Comsol's "boundary distance variables" might be of help to you.
If you remove the attraction at some (very small) distance to the wall, the streamlines should never touch the wall. If they still touch and disappear you could make the wall repellant at some (very small) distance. If believe Comsol's "boundary distance variables" might be of help to you.
Daniel Hankins
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Posted: 1 decade ago Feb 3, 2011, 7:17 p.m. EST
I am new to COMSOL and just using it for simulating experiments for a summer research scolarship for uni, so I dont know what boundary distance variables are. other than that, ive tried everything I can think off and it either doesnt work or I dont know enough to get it to.

if you can easily explain or something about the variables, ill give them a go when ive got time. otherwise thanks for your input, but I havent found a solution and I need to start finishing up, so ill go with what ive got.
I am new to COMSOL and just using it for simulating experiments for a summer research scolarship for uni, so I dont know what boundary distance variables are. other than that, ive tried everything I can think off and it either doesnt work or I dont know enough to get it to. if you can easily explain or something about the variables, ill give them a go when ive got time. otherwise thanks for your input, but I havent found a solution and I need to start finishing up, so ill go with what ive got.
Saurin Patel
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Posted: 1 decade ago Mar 1, 2011, 3:06 p.m. EST
I have similar problem of streamlines going on the wall and disappearing for the attraction force of positive DEP force.
I also tried to use Boundary distance variable but was not able to get results. Or any help regarding the specific use of boundary distance variable would be handy.

As far as repulsive force is concerned i think the geometry is to complex to assign a uniform repulsive force. Any idea removing the attraction force very near to the boundary will be of help.
I have similar problem of streamlines going on the wall and disappearing for the attraction force of positive DEP force. I also tried to use Boundary distance variable but was not able to get results. Or any help regarding the specific use of boundary distance variable would be handy. As far as repulsive force is concerned i think the geometry is to complex to assign a uniform repulsive force. Any idea removing the attraction force very near to the boundary will be of help.

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