Yade

Particles fall through facets in periodic simulation

Asked by Bettina Suhr

Dear all,

I would like to generate a packing of clumps inside a box, where at front and back of the box periodic boundary conditions are applied. At first, I defined the periodic cell and then added a facet box (without the front and back side) inside the cell. The problem is that when the clumps fall down due to gravity, some clumps go through the bottom of my facet box. I think that this problem is not related to the young modulus of the material or the time step size: When I define my box with facets at front and back, the problem does not occur. Can anybody explain me, what is the problem? Below you find my minimal working example.

Thanks a lot,
Bettina

from yade import pack

O.materials.append(FrictMat(young=1e10, poisson=0.28, frictionAngle=0.2, density=2600.))
O.engines=[
 ForceResetter(),
 InsertionSortCollider([Bo1_Sphere_Aabb(), Bo1_Wall_Aabb(), Bo1_Facet_Aabb()],allowBiggerThanPeriod=True),
 InteractionLoop(
   [Ig2_Sphere_Sphere_ScGeom(), Ig2_Facet_Sphere_ScGeom(), Ig2_Wall_Sphere_ScGeom()],
   [Ip2_FrictMat_FrictMat_FrictPhys()],
   [Law2_ScGeom_FrictPhys_CundallStrack()]
 ),
 NewtonIntegrator( gravity=(0,0,-9.81),label='newtonEng')# NO DAMPING
]

Len=700e-3
Wid=120e-3
H=450e-3+100e-3
O.periodic=True
O.cell.setBox(Wid,Len+1e+0,H+1e+0)

#add box
#wall mask: -x (1), +x (2), -y (4), +y (8), -z (16), +z (32).
O.bodies.append(geom.facetBox(center=(Wid/2.,Len/2.+0.5e+0,H/2.+0.5e+0),extents = ( Wid/2.,Len/2.,H/2.), wallMask=3+4+8+16+32, color=(1,0,0)))

#create pack of clumps in box
sp=pack.SpherePack()
Num=100
c1=pack.SpherePack([ ((0.,0.,0.),37.6e-3/2.), ((37.6e-3/2.,0.,0.),25e-3/2.) ])# overlap (!) between both spheres
sp.makeClumpCloud( (0,0+0.5e+0,0+0.5e+0), ( Wid,Len+0.5,H+0.5), [c1],num=Num,seed=1)
ballastID=sp.toSimulation()
O.bodies.updateClumpProperties(discretization=10)# correct mass, volume, inertia!!

O.dt=0.5*PWaveTimeStep()

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Jérôme Duriez (jduriez) said : 		#1

Hello,

I have no answer but, as a comment, you're not the first one to face difficulties in non-completely periodic simulations, see
https://answers.launchpad.net/yade/+question/275284 and links therein.

Maybe this issue will one day be seriously considered and solved ? (assuming it is related to your problem)

Jerome

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Anton Gladky (gladky-anton) said : 		#2

I do not see anything weird there (standard yade_1.20.0). Particles are falling down and settle there.
Blinking wired particles are just particles, which are crossing the periodic boundary, but later they return
back to the normal position and its wired structures disappears.

Please test it and let us know, whether it works.

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Bettina Suhr (bettina-suhr) said : 		#3

Hi Jerome and Anton,

thank you very much for your answers.

@Anton: I’m sorry, there’s a typo in the wallMask in the definition of the facet box (at the moment there are facets at the front and back. In this case everything is fine.) If you replace the definition of the box with:
O.bodies.append(geom.facetBox(center=(Wid/2.,Len/2.+0.5e+0,H/2.+0.5e+0),extents = ( Wid/2.,Len/2.,H/2.), wallMask=4+8+16+32, color=(1,0,0)))
you should see the problem. I also use yade_1.20.0

@Jerome: Thank you for posting the link to the other question, I didn’t see it before. There might be a problem with InsertionSortCollider then for periodic cases. It would be nice, if it could be solved at some moment. Probably not an easy task, though …

Regards,
Bettina

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VG (varun-gupta) said : 		#4

Hello Bettina,

Were you able to resolve this issue or find a work around ? I continue to face this problem and have posted a minimal working example at : https://answers.launchpad.net/yade/+question/290950

The top and bottom plates are far apart (more than 3 times the diameter of particles) to start with, but the top plate still goes through the particles and even bottom plate eventually.

Thanks
Varun

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Bettina Suhr (bettina-suhr) said : 		#5

Hi Varun,

thanks for the notice. No, I didn‘t find a solution or a work around.
Using your minimal working example resulted in the same problem as you reported (I use yade-1.20.0). Also, the work around Bruno suggested doesn’t work for me. It seems that at the current state periodic boundary conditions can not be used with walls/boxes or facets.

Best regards,
Bettina

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VG (varun-gupta) said : 		#6

Thanks for your response, Bettina!
Yes the work around which Bruno suggested doesn't work for me either.

May be I will have to change the problem set up, but at this point I don't know how I could achieve that and still keep it physically realistic. I need to compress the granular material with a constant force or leading to a constant compressive stress and then induce shear stress (currently doing it through the velocity of plate) to study the breakage of granular material. Please let me know if you have any suggestions.

Thanks
Varun

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