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[jduriez <question246392@xxxxxxxxxxxxxxxxxxxxx>]

New question #246392 on Yade:
https://answers.launchpad.net/yade/+question/246392

Hi,

I'm lost about the contact between box or wall with spheres with periodic boundaries (this is not related to the allowBiggerThanPeriod flag, that I'm using).

Consider 9 spheres lying on a box, in a periodic cell. The cell includes exactly the 9 spheres, and the box may change in size. Its surface may approach the one of the cell, or may be bigger (see script below)

   - if the surface of the box is 90% the one of the cell (set howBig = 0.45 in the script below), I get my 9 sphere-box interactions, fine !
   - if the box fills exactly (in surface) the cell (howBig = 0.5) => only 6 spheres are detected as in contact with the box.. (or 4 if I put   radius = 0.5, so that there is normally exact geometrical contact)
   - if howBig = 0.6 (the box extends beyond the limits of the cell) => 6 spheres in contact, for both radii tested (0.5 - exact contact - or 0.55 - overlap)
   - if howBig = 1000 => there are 3 spheres in contact with the box.....

If I use a wall I got 3 spheres-wall contact for radius = 0.5, and 6 for radius = 0.55, but not 9.... May someone explain to me these results ? (or confirm that there is a bug ?)

Jérôme

PS : the script :
# encoding: utf-8

O.periodic=1
O.cell.setBox(3,3,3)
for i in range(0,3):
    for j in range (0,3):
        O.bodies.append(sphere(center=Vector3(i+0.5,j+0.5,1.5),radius=0.55,dynamic=0))

howBig=0.45
O.bodies.append(box(center=Vector3(1.5,1.5,0.9),extents=Vector3(howBig*3,howBig*3,0.1)))

O.engines=[
	ForceResetter()
	,InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Box_Aabb()],allowBiggerThanPeriod=1)
	,InteractionLoop(
		[Ig2_Sphere_Sphere_ScGeom(),Ig2_Box_Sphere_ScGeom()],
		[Ip2_FrictMat_FrictMat_FrictPhys()],
		[Law2_ScGeom_FrictPhys_CundallStrack()])
        ,NewtonIntegrator(damping=0.2)
	]

O.dt=1.e-5
O.step()

print '\nhowBig =',howBig,':', O.interactions.withBody(9).__len__(),'interactions with the box\n'

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