Re: [Yade-users] [Question #681232]: Sphere goes through the facet wall in Harmonic vibration
Question #681232 on Yade changed: https://answers.launchpad.net/yade/+question/681232 gaoxuesong posted a new comment: Hi Jan, Thanks for your answers. For the density magnification, in my case, the diameter of the sphere is around 80 um. If i use the normal density, it costs about 4 hours to simulate virtual time of 55 ms. The total time i need is 3s, so it is very time-consuming. In my method, the last step is mass shrinking, where the mass of all the particles is gradually decreased to the 1/1000 of the used value. Does it make sense or do you have good advice? -- 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 #681246]: something do not understand about code in polyhedra_ig2.cpp
Question #681246 on Yade changed: https://answers.launchpad.net/yade/+question/681246 Status: Open => Answered Jan Stránský proposed the following answer: Hello, > question1 for non-periodic simulations, it is Vector3(0,0,0) for periodic simulations, is is shift of the second body to make the interaction meaningful > question2 se31.position would be in python state.pos **usually** it is the center of mass. But in general b.state.pos and b.shape.v can be quite independent. 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 #681246]: something do not understand about code in polyhedra_ig2.cpp
New question #681246 on Yade:
https://answers.launchpad.net/yade/+question/681246
hello
below is the code i am reading:
bool Ig2_Polyhedra_Polyhedra_ScGeom::go(const shared_ptr& shape1, const
shared_ptr& shape2, const State& state1, const State& state2, const
Vector3r& shift2, const bool& force, const shared_ptr&
interaction) {
const Se3r& se31=state1.se3;
const Se3r& se32=state2.se3;
shared_ptr geom;
bool isNew = !interaction->geom;
if (isNew) {
Ig2_Polyhedra_Polyhedra_PolyhedraGeom ppGeom =
Ig2_Polyhedra_Polyhedra_PolyhedraGeom();
ppGeom.interactionDetectionFactor = interactionDetectionFactor;
bool pp =
ppGeom.go(shape1,shape2,state2,state1,shift2,force,interaction);
if (!pp) {
return false;
}
shared_ptr pGeom =
YADE_PTR_CAST(interaction->geom);
geom = shared_ptr(new ScGeom());
geom->radius1 = (pGeom->contactPoint-se31.position).norm();
geom->radius2 =
(pGeom->contactPoint-se32.position+shift2).norm();
interaction->geom=geom;
} else {
geom = YADE_PTR_CAST(interaction->geom);
}
const Real& radius1 = geom->radius1;
const Real& radius2 = geom->radius2;
Vector3r normal=(se32.position+shift2)-se31.position;
Real norm=normal.norm(); normal/=norm; // normal is unit vector now
Real penetrationDepth=radius1+radius2-norm;
geom->contactPoint=se31.position+(radius1-0.5*penetrationDepth)*normal;//0.5*(pt1+pt2);
geom->penetrationDepth=penetrationDepth;
scene = Omega::instance().getScene().get();
geom->precompute(state1,state2,scene,interaction,normal,isNew,shift2,false);
return true;
}
question1: what does the parameter shift2 do?
question2:what does se31.position refer to? i know that the position of sphere
means the centre of it, but as to polyhedra, which point can define the
position of it? Is the positon means the centroid of polyhedra or something
else?
lookforward for your answer.
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Re: [Yade-users] [Question #680963]: how to set different stress paths
Question #680963 on Yade changed: https://answers.launchpad.net/yade/+question/680963 Status: Open => Expired Launchpad Janitor expired the question: This question was expired because it remained in the 'Open' state without activity for the last 15 days. -- 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 #681232]: Sphere goes through the facet wall in Harmonic vibration
Question #681232 on Yade changed: https://answers.launchpad.net/yade/+question/681232 Status: Open => Answered Jan Stránský proposed the following answer: Hello, > Then the piston does harmonic vibration. I find when the vibration amplitude goes to high, the spheres go through the piston, which is constructed by facet. I want to know the reason and fix it. There might be several issues: a) the piston period is to short w.r.t O.dt that the piston simply "overjumps" the particles, not interacting with them at all b) the stiffness/mass/timestep combination is such that the repulsive force acts so little time, has so liitle magnitude etc. that the piston is not able to "push away" the particles. c) Linear contact law also does not help b) as for really high penetration, the force is "too low" > In addition, the density is amplified by a factor of 1e9 to increase the calculation speed. by increasing density, you can get higher critical time step. BUT you also change the physics of the system (see point b above). It always depends if and which values are acceptable. 1e9 * density sounds really too much.. If you want to get "realistic" results of a dynamic system, **in my opinion** this is not the way to go.. Somewhat less drastic scenario is to increase mass of some fraction (e.g. 5% of mass) of the smallest particles. It increases time step (determined by the smallest particles), but preserves dynamic properties of the "most" of the system. > And also I want to know how to define the word of "rigid" in yade. In my > case, the box is rigid and the spheres are relatively soft. > Does it make sense if i set the young's modulus of the box material as 100 > times of that of the sphere material? the stiffness of interaction is computed as a harmonic average of stiffness of individual bodies, something like E=2*E1*E2/(E1+E2) The limit for E2->infinity is E=2*E1. For E2=100*E1, E=1.98, so it could be "close enough" to rigid. 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
