# Zero force and torque on clumps

0 votes
60 views
asked Feb 9, 2018

Hi!

I would like to sum the torque values collected from clump members on an axis of a mixer. My problem is that all the force and torque vectors are zero despite of there are visible collisions between the particles and the mixer.

Here's my code:

import woo, math
from woo import utils
from woo.core import *
from woo.dem import *
from woo import plot
from woo import *
from minieigen import *

# scene:
S=woo.master.scene=woo.core.Scene(fields=[DemField(gravity=(0,-9.81,0))])

n=1
loadfactor=15
angularvel=2*math.pi*n

#model locations
drumlocation='/home/dem/woo/drum_k.stl'
mixerlocation='/home/dem/woo/mixer_k.stl'

#computing volume from load factor
Vmax=.01234
V=(Vmax/25)*loadfactor
Hdep=(V/.14)+.1

#drum mixer's geometry
drum=S.dem.par.add(woo.utils.importSTL(drumlocation,mat=woo.utils.defaultMaterial(),readColors=False,color=-.25))
mixer=woo.utils.importSTL(mixerlocation,mat=woo.utils.defaultMaterial(),readColors=False,color=.5)
S.lab.mixNode=Node(pos=(0,0,0),dem=ClumpData(blocked='xyzXYZ'),ori=Quaternion((0,0,1),math.pi/2.))
global kevero
mixerelement=S.dem.par.addClumped(mixer,centralNode=S.lab.mixNode)
S.lab.mixNode.dem.angVel=(0,0,angularvel)

#particles
sp=woo.pack.SpherePack()
sp.makeCloud((-.1,.1,-.35),(.1,Hdep,.35),rMean=.005,rRelFuzz=.001,num=300000)
sp.toDem(S,mat=woo.utils.defaultMaterial(),color=.4)

S.dtSafety=1
S.saveTmp()
from woo import qt
v=qt.View()
v.eyePosition=(-0.8,.3,.8);v.upVector=(0,1,0);v.viewDir=(.8,-0.3,-0.7)

# engines:
S.engines=S.dem.minimalEngines(damping=.2)+[PyRunner(5,'printData(S)')]

def printData(S):
print ClumpData.forceTorqueFromMembers(mixerelement)	

Any suggestions?

Thanks,

D

commented Feb 14, 2018 by (48,950 points)

Hi, strange. I will prepare some minimal mixer simulation and will let you know. Please be patient, a few days. Or you could send me complete simulation source so that I can reproduce easily, perhaps by e-mail (see my contact at woodem.eu). Cheers, vaclav

## 1 Answer

0 votes
answered Feb 15, 2018 by (48,950 points)
selected Feb 15, 2018

Best answer

I added an example here https://github.com/woodem/woo/blob/master/examples/mixer.py , also with explanations. You have to transfer contact forces to facet nodes first, done via woo.dem.IntraForce([woo.dem.In2_Facet()]) engine.

All the best, Vaclav

commented Feb 15, 2018 by (350 points)

Thank you very much Vaclav!

Best regards,
D