problem using the hopper example with smaller particles

Hi,
Using the clump-hopper-test located at trunk/examples/clumps/clump-hopper-test.py, I have tried modifying it to work with smaller particles. I am using this example to test out the timestep required for simulating gravity deposition of nanometer sized particles. I have modified the example to use a scaling factor, which allows the generated geometry to be scaled down. My plan is to scale everything down to 1e-6. However, no matter the timestep used, the particles pass right through the facetbox. Even with a timestep of 5e-09, where the particles hardly move, the particles pass right through.

Is it possible to run this gravity simulation with small (50e-09) particles? Reducing the timestep even further doesnt seem to be the way to go here.

Your help always appreciated
Jesse

The script I have pasted below.

from yade import pack,export,qt,geom
import itertools
from numpy import *

scalefac = 1e-6 #be careful of timestep

kinEnergyMax = 100000
# Parameters
tc=0.001# collision time
en=.3 # normal restitution coefficient
es=.3 # tangential restitution coefficient
frictionAngle=radians(35)#
density=2700
# facets material
facetMat=O.materials.append(ViscElMat(frictionAngle=frictionAngle,tc=tc,en=en,et=es))
# default spheres material
dfltSpheresMat=O.materials.append(ViscElMat(density=density,frictionAngle=frictionAngle,tc=tc,en=en,et=es))

#O.dt=.05*tc # time step
O.dt=.05*tc * 1e-3# time step
#O.dt= 1e-09

Rs=0.05 # particle radius

# Create geometry

x0=0.; y0=0.; z0=0.; ab=.7; at=2.; h=1.; hl=h; al=at*3

Rs *= scalefac
ab *= scalefac
at *= scalefac
h *= scalefac

zb=z0; x0b=x0-ab/2.; y0b=y0-ab/2.; x1b=x0+ab/2.; y1b=y0+ab/2.
zt=z0+h; x0t=x0-at/2.; y0t=y0-at/2.; x1t=x0+at/2.; y1t=y0+at/2.
zl=z0-hl;x0l=x0-al/2.; y0l=y0-al/2.; x1l=x0+al/2.; y1l=y0+al/2.

vibrationPlate = O.bodies.append(geom.facetBunker((x0,y0,z0),
  dBunker=ab*4.0,dOutput=ab*1.7,hBunker=ab*3,hOutput=ab,hPipe=ab/3.0,
  wallMask=4,segmentsNumber=10))#,material=facetMat))

# Create engines
O.engines=[
 ForceResetter(),
 InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb()]),
 InteractionLoop(
  [Ig2_Sphere_Sphere_ScGeom(), Ig2_Facet_Sphere_ScGeom()],
  [Ip2_ViscElMat_ViscElMat_ViscElPhys()],
  [Law2_ScGeom_ViscElPhys_Basic()],
 ),
 DomainLimiter(lo=(-4,-4,-1),hi=(4,4,4),iterPeriod=5000,label='domLim'),
 NewtonIntegrator(damping=0, gravity=[0,0,-9.81]),
 PyRunner(iterPeriod=6500,command='addBodies()',nDo=7,label='addb'),
 PyRunner(iterPeriod=1000,command='state()',label='state'),
]

numSphereGen = 0
def addBodies():
 global numSphereGen
 # Create clumps...
 clumpColor=(0.0, 0.5, 0.5)
 for k,l in itertools.product(arange(0,10),arange(0,10)):
  #clpId,sphId=O.bodies.appendClumped([sphere(Vector3(x0t+Rs*(k*4+2),y0t+Rs*(l*4+2),i*Rs*2+zt+ab*3),Rs,color=clumpColor,material=dfltSpheresMat) for i in xrange(4)])
  clpId,sphId=O.bodies.appendClumped([sphere(Vector3(x0t+Rs*(k*4+2),y0t+Rs*(l*4+2),i*Rs*2+zt+ab*3),Rs,color=clumpColor) for i in xrange(4)])
  numSphereGen += len(sphId)

 # ... and spheres
 spheresColor=(0.4, 0.4, 0.4)
 for k,l in itertools.product(arange(0,9),arange(0,9)):
  #sphAloneId=O.bodies.append( [sphere( Vector3(x0t+Rs*(k*4+4),y0t+Rs*(l*4+4),i*Rs*2.3+zt+ab*3),Rs,color=spheresColor,material=dfltSpheresMat) for i in xrange(4) ] )
  sphAloneId=O.bodies.append( [sphere( Vector3(x0t+Rs*(k*4+4),y0t+Rs*(l*4+4),i*Rs*2.3+zt+ab*3),Rs,color=spheresColor) for i in xrange(4) ] )
  numSphereGen += len(sphAloneId)

 #O.bodies.updateClumpProperties(discretization=10)# correct mass, volume, inertia!!

def state():
 global numSphereGen
 print "Iter %d: Total number of generated spheres %d, removed particles %d, current particles %d, kinEnergy %g"%(O.iter, numSphereGen, domLim.nDeleted, numSphereGen-domLim.nDeleted, utils.kineticEnergy())
 if (utils.kineticEnergy() > kinEnergyMax):
  print "Kinetic energy is over a threshold value! Error!"

addBodies()

from yade import qt
qt.View()
O.saveTmp()

#O.run(50001)