[Yade-users] [Question #665379]: penetrationDepth calculation
New question #665379 on Yade: https://answers.launchpad.net/yade/+question/665379 Hi, I would like to understand the way "penetrationDepth" is calculated. For instance, in a simple collision between two identical spheres I've seen that it does not correspond to x1-x2-2*r where r is the radius of the spheres. I've been looking into the code and found for instance in Sphere_Sphere_ScGeom https://github.com/yade/trunk/blob/master/pkg/dem/Ig2_Sphere_Sphere_ScGeom.cpp (line 21) that the distance is shifted by a vector "shift2" which is passed to the function Vector3r normal=(se32.position+shift2)-se31.position; but whose definition I cannot trace back I suspect that this serves the purpose of interlaced force evaluation for runge kutta etc. but I would like to have a confirmation Thanks for any help Andrea -- 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 #665379]: penetrationDepth calculation
Question #665379 on Yade changed: https://answers.launchpad.net/yade/+question/665379 Status: Open => Answered Jan Stránský proposed the following answer: Hello Andrea, shift2 is used for periodic contact detection, have a look at [1]. See [2] for the meaning of Interaction::cellDist. cheers Jan [1] https://github.com/yade/trunk/blob/master/pkg/common/InteractionLoop.cpp#L113 [2] https://yade-dem.org/doc/formulation.html#collision-detection-in-periodic-cell -- 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 #665379]: penetrationDepth calculation
Question #665379 on Yade changed: https://answers.launchpad.net/yade/+question/665379 Bruno Chareyre proposed the following answer: Hi, It does correspond to x1-x2-2*r. Cheers 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 #665379]: penetrationDepth calculation
Question #665379 on Yade changed:
https://answers.launchpad.net/yade/+question/665379
Status: Answered => Open
Andrea Puglisi is still having a problem:
Thanks Jan and Bruno. From Jan'answer I understand that the variable
shift2 should not be a problem in my example (I have no periodicity, it
is just a collision between two spheres). From Bruno's answer I learn
that there is something wrong in my script where I measure both the
quantity overlap=2*r-(x2-x1) (I have x2>x1) and the quantity
interaction.geom.penetrationDepth and they do not coincide.
My script is the following. The graph of the two quantity penetrationDepth vs.
overlap can be found at this shared link
https://drive.google.com/file/d/1r6YWwbg56jIN3EGB4RzoBRGHgHyHAhir/view?usp=sharing
#!/usr/bin/python
# -*- coding: utf-8 -*-
from yade import pack,ymport,export,geom,bodiesHandling,qt,plot
import math
rad = 0.00774
f=open("forces.dat" , "w")
def forces():
x1 = O.bodies[0].state.pos[0]
v1 = O.bodies[0].state.vel[0]
v2 = O.bodies[1].state.vel[0]
x2 = O.bodies[1].state.pos[0]
ov = 2*rad-(x2-x1)
intrs = O.bodies[0].intrs()
if (len(intrs)):
nfx = intrs[0].phys.normalForce[0]
nfy = intrs[0].phys.normalForce[1]
nfz = intrs[0].phys.normalForce[2]
sfx = intrs[0].phys.shearForce[0]
sfy = intrs[0].phys.shearForce[1]
sfz = intrs[0].phys.normalForce[2]
dep = intrs[0].geom.penetrationDepth
else:
nfx = nfy = nfz = sfx = sfy = sfz = dep = 0
f.write ("%6d %12.8f %12.8f %12.8f %12.8f %9.6f %9.6f %9.6f %9.6f %9.6f
%9.6f %12.8f\n" % (O.iter,O.time,ov,v1,v2,nfx,nfy,nfz,sfx,sfy,sfz,dep))
f.flush()
O.materials.append(FrictMat(young=0.1e9,poisson=.22,frictionAngle=0,density=2300,label='glass'))
Sph_1 = O.bodies.append([sphere([0,0,0], radius=rad, material = "glass")])
Sph_2 = O.bodies.append([sphere([0.1,0,0], radius=rad, material = "glass")])
O.bodies[1].state.vel = Vector3(-0.3,0,0)
O.bodies[0].state.vel = Vector3(0.3,0,0)
O.engines=[
ForceResetter(),
InsertionSortCollider([Bo1_Sphere_Aabb(),
],label='collider'),
InteractionLoop(
[Ig2_Sphere_Sphere_ScGeom()],
[Ip2_FrictMat_FrictMat_MindlinPhys()],
[Law2_ScGeom_MindlinPhys_Mindlin()],
),
NewtonIntegrator(damping=0.0,exactAsphericalRot=True,gravity=(0,0,0)),
PyRunner(command='forces()', iterPeriod=1),
]
O.dt=PWaveTimeStep()
try:
from yade import qt
qt.Controller()
qt.View()
except ImportError: pass
O.saveTmp()
O.timingEnabled=True
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Re: [Yade-users] [Question #665379]: penetrationDepth calculation
Question #665379 on Yade changed: https://answers.launchpad.net/yade/+question/665379 Status: Open => Solved Andrea Puglisi confirmed that the question is solved: A, I've understood my error! The overlap contained in penetrationDepth is the one computed for the force, which corresponds to positions at the previous step! Sorry to make you lose your precious time and thanks for help anyway! -- 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
