Re: [Yade-users] [Question #452513]: overlapping particle/particle and particle/wall
Question #452513 on Yade changed: https://answers.launchpad.net/yade/+question/452513 Status: Answered => Solved Michael Kolbeck confirmed that the question is solved: thank all of you! @Jerome: I'll try playing around with the particle stiffness @Bruno: You are right. Defined contact points between particle/particle and particle/wall result in highly skewed cells or a highly increased number of cells (but the overlap makes the problem just a little bit less worse). I just wanted to have an initial state from which I can start (since I don't know how much the particles overlap). -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #452513]: overlapping particle/particle and particle/wall
Question #452513 on Yade changed: https://answers.launchpad.net/yade/+question/452513 Bruno Chareyre proposed the following answer: >"is there a way to minimize the overlap?" You can decrease confining pressure or increase material stiffness. The result will be the same both ways: less overlap, more cpu time. I am actually wondering if it is not helping to have overlaps for the fluent part of the problem. When the spheres are exactly tangent to the walls it is horribly demanding in terms of mesh refinement if you want to capture what happens near the tangent point (in fact a lubrication problem). Just curious. Bruno -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #452513]: overlapping particle/particle and particle/wall
Question #452513 on Yade changed: https://answers.launchpad.net/yade/+question/452513 Bruno Chareyre proposed the following answer: "decrease confining pressure" should be "decrease gravitational acceleration" in this particular case. I just realized. B -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #452513]: overlapping particle/particle and particle/wall
Question #452513 on Yade changed: https://answers.launchpad.net/yade/+question/452513 Status: Open => Answered Jérôme Duriez proposed the following answer: In fact, there actually is some kind of DEM (Non Smooth Contact Dynamics) which sticks to the rigid bodies point of view, and do not use any overlap. YADE does not belong to this category, though.. In order to minimize interparticles overlap for a given stress state (which is indeed given in a gravity deposition simulation), just use higher particle stiffnesses i.e. FrictMat.young parameter (here it seems you're using the default 1e7 value since you do not explicitly define material parameters). Nothing to do with engines list in such case. -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #452513]: overlapping particle/particle and particle/wall
Question #452513 on Yade changed: https://answers.launchpad.net/yade/+question/452513 Status: Answered => Open Michael Kolbeck is still having a problem: Hi Jan, thank you for your answer. I see that using DEM, there is no way to avoid overlap. But is there a way to minimize the overlap? for example by modifying the material properties or the engine modification. Cheers, Michael -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #452513]: overlapping particle/particle and particle/wall
Question #452513 on Yade changed: https://answers.launchpad.net/yade/+question/452513 Status: Open => Answered Jan Stránský proposed the following answer: Hi Michael, I'm new with Yade Welcome :-) the basic idea of DEM is that inter-particle forces depends on mutual overlap (linearly in the most basic case). So if you apply gravity and the sample is supposed to be in static equilibrium, overlaps are intrinsic part of the situation. One solution is to enlarge particles slightly before simulation and shrink them back to original size afterwards. In this case there will be no overlaps, but the particles would not be touching at the same time (both mutually and also between particle-wall). To make particles just touching the walls, you can shrink the particles individually to fulfill exactly the condition of touching. cheers Jan -- You received this question notification because your team yade-users is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
[Yade-users] [Question #452513]: overlapping particle/particle and particle/wall
New question #452513 on Yade:
https://answers.launchpad.net/yade/+question/452513
Hello everyone,
I'm new with Yade and I would appreciate some help.
I need to create a random dense packing in a cylinder. The radii of the spheres
should have a normal distribution around a given value. Furthermore the spheres
should not overlap, and the particles close to the cylinder surface should
touch the surface (but not intersect the cylinder wall). Then I export the
coordinates for further analysis in Ansys Fluent.
I first create a particle cloud in my predicate and then apply gravity
deposition while my predicate is shaking (to distribute the particles evenly
over the whole cross section of the cylinder). After 8000 iterations I stop
the simulation and export the coordinates:
from yade import pack, qt, export
cylinder=O.bodies.append(geom.facetCylinder(center=(0,0,125),radius=15,height=250,segmentsNumber=100,wallMask=7,closeGap=True))
sp=pack.SpherePack()
diameter=[3.600,3.640,3.680,3.720,3.760,3.800,3.840,3.880,3.920,3.960,4.000,4.040,4.080,4.120,4.160,4.200,4.240,4.280,4.320,
4.360,4.400,4.440,4.480,4.520,4.560,4.600,4.640,4.680,4.720,4.760,4.800,4.840,4.880,4.920,4.960,5.000,5.040,5.080,
5.120,5.160,5.200,5.240,5.280,5.320,5.360,5.400]
cum=[0.001,0.002,0.003,0.005,0.007,0.010,0.014,0.019,0.027,0.036,0.048,0.063,0.081,0.103,0.129,0.159,0.193,0.232,0.274,
0.320,0.369,0.421,0.473,0.527,0.579,0.631,0.680,0.726,0.768,0.807,0.841,0.871,0.897,0.919,0.937,0.952,0.964,0.973,
0.981,0.986,0.990,0.993,0.995,0.997,0.998,1.000]
sp.makeCloud((-10,-10,200),(10,10,245),psdSizes=diameter,psdCumm=cum,distributeMass=False)
sp.toSimulation()
yade.qt.Controller()
yade.qt.View()
O.engines=[
ForceResetter(),
InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb()]),
InteractionLoop(
[Ig2_Sphere_Sphere_ScGeom(),Ig2_Facet_Sphere_ScGeom()],
[Ip2_FrictMat_FrictMat_FrictPhys()],
[Law2_ScGeom_FrictPhys_CundallStrack()]
),
HarmonicMotionEngine(A=[0,1.5,0],f=[0,0.3,0],ids=cylinder),
NewtonIntegrator(gravity=(0,0,-9.81),damping=0.5),
PyRunner(command='iterations()',realPeriod=2)
]
O.dt=.5*PWaveTimeStep()
def iterations():
O.stopAtIter=8000
export.text('pack.txt')
Then I start another simulation, create the same predicate, import the packing
and then apply a simple gravity deposition and let it "rest" until the
unbalanced force is below 0.001:
from yade import pack, qt, ymport, export
cylinder=O.bodies.append(geom.facetCylinder(center=(0,0,125),radius=15,height=250,segmentsNumber=100,wallMask=7,closeGap=True))
packing=ymport.text('pack.txt',scale=1.0)
O.bodies.append(packing)
yade.qt.Controller()
yade.qt.View()
O.engines=[
ForceResetter(),
InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb()]),
InteractionLoop(
# handle sphere+sphere and facet+sphere collisions
[Ig2_Sphere_Sphere_ScGeom(),Ig2_Facet_Sphere_ScGeom()],
[Ip2_FrictMat_FrictMat_FrictPhys()],
[Law2_ScGeom_FrictPhys_CundallStrack()]
),
NewtonIntegrator(gravity=(0,0,-9.81),damping=0.5),
PyRunner(command='checkUnbalanced()',realPeriod=2)
]
O.dt=.5*PWaveTimeStep()
def checkUnbalanced():
if unbalancedForce()<.001:
O.pause()
export.text('pack1.txt')
But when I import my pack into Ansys Fuent (generating the spheres in CATIA V5
first), the particles overlap sligthly among each other and intersect with the
drawn cylinder wall.
And now my question: Why is that so and is there a way to avoid this problem?
Many thanks,
Michael
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