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Hiting the Wall by the Particles

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Old   March 4, 2010, 07:00
Default Hiting the Wall by the Particles
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Hello!
I have a problem with the particles tracking. The problem is to simulate the hit of the particle to the wall (the boundary of the mesh) correctly.
There is solidParticle library in the OpenFOAM. The function trackToFace in solidParticle.C detects the situation when the particle hits the wall and changes the direction of the velocity of the particle.
But I want to simulate the situation when the particle has the size. Thus trackToFace function should detect when the boundary of the particle hits the wall, but not the center of particle does this.

Can you tell me where should I subtract the radius of the particle?
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Old   March 8, 2010, 21:29
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The particle diameter is taken into account when it hits a patch, however, after a quick look in the code, I can't find where.

This works ok as long as your particle is much smaller than the cell size. if this is not the case, then particles can miss the wall, due to not being in the adjacent cell.

Also, the default drag model in solidParticle is not the greatest - what are you trying to simulate?

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Old   March 8, 2010, 21:31
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Actually, I've had a closer look. The wall impact distance check is in lagrangian/basic/Particle/ParticleI.H

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Old   March 9, 2010, 01:33
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Thank you for answer, Andrew!
wallImpactDistance return a half of the diameter.
But, as you said, the problem is to take into account particle size when it is more then cell size. It my case it is so!
I simulate the particles motion in turbulent flow. Of course I use not a solidParticle library, but my own one that was created on the base of solidParticle. To simulate correctly the flow near the walls I should use small cells there. Thus the problem steel exist in my case.
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Old   March 9, 2010, 01:41
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Hi Mihails,

We are facing the same problem. The way that I am proposing to do it, though haven't implemented yet, is to define a static (as in non-changing) wall-distance field.

This distance can then be checked against the particle diameter to see whether a patch (or wall) has been hit.

I'm not sure of the performance implications of this yet however. I think that the overhead shouldn't be too bad though.

Any comments or suggestions are welcome.

Andrew
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Old   March 9, 2010, 02:17
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The main problem is so. I can not understand how collision of particle and wall is indicated in this library. How is calculated the distance from particle center to the wall? And where it is compared with wallImpactDistance?
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Old   March 9, 2010, 03:14
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I should understand it to valuate your way of solving problem or give some suggestions.
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Old   March 10, 2010, 22:04
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The key parts are in lagrangian/basic/Particle/ParticleI.H and lagrangian/solidParticle/solidParticle.{C,H} you should be able to follow the code. See the Doxygen for more info. http://foam.sourceforge.net/doc/Doxygen/html/

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Old   March 15, 2010, 13:43
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Andrew,
I made the simple thing, I put if in move function in solidParticle.C. So if the distance from the particle center to the wall is less than the radius of the particle, then I shift it to the distance of the radius the wall.
Such a modification allow me to obtain the good physical results.
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Old   April 12, 2010, 04:22
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Andrew,
the problem of correct simulation of particle collision with the wall actualized now again!
Did you solve this problem already?
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