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[Chareyre <question680215@xxxxxxxxxxxxxxxxxxxxx>]

Question #680215 on Yade changed:
https://answers.launchpad.net/yade/+question/680215

    Status: Open => Answered

Chareyre proposed the following answer:
Indeed. In order to avoid very complex corner cases (since every engine can
change it and depends on it) I decided that the assigned velocity gradient
would be taken into account only at the next step.
You can maybe force it with prevVelGrad.
Bruno

Le ven. 12 avr. 2019 19:22, zhou qian <question680215@xxxxxxxxxxxxxxxxxxxxx>
a écrit :

> New question #680215 on Yade:
> https://answers.launchpad.net/yade/+question/680215
>
> Hi:
> I defined a periotric cell and found that in the first step, the trsf
> didn't change.
> Here are the codes,
> import libyade
>
> from libyade import*
> from libyade import utils, pack, Matrix3, Vector3, Vector3
> import datetime
>
> def randomPeriPack(radius,initSize,seed):
>         O.switchScene(); O.resetThisScene()
>         sp=pack.SpherePack()
>         O.periodic=True
>         O.cell.setBox(initSize)
>
> sp.makeCloud(Vector3().Zero,O.cell.refSize,radius,0.,-1,True,seed=seed)
>         O.engines=[
>                 ForceResetter(),
>
> InsertionSortCollider([Bo1_Sphere_Aabb()],verletDist=.05*radius),
>                 InteractionLoop(
>                         [Ig2_Sphere_Sphere_ScGeom()],
>                         [Ip2_FrictMat_FrictMat_FrictPhys()],
>                         [Law2_ScGeom_FrictPhys_CundallStrack()]),
>
> PeriIsoCompressor(charLen=2*radius,stresses=[-100e9,-1e8],maxUnbalanced=1e-2,doneHook='O.pause();',globalUpdateInt=20,keepProportions=True),
>                 NewtonIntegrator(damping=.8)
>         ]
>
> O.materials.append(FrictMat(young=30e9,frictionAngle=.1,poisson=.3,density=1e3))
>         for s in sp: O.bodies.append(utils.sphere(s[0],s[1]))
>         O.dt=utils.PWaveTimeStep()
>         O.timingEnabled=True
>         O.run(); O.wait()
>         for b in O.bodies: b.state.pos = O.cell.wrap(b.state.pos)
>         ret=pack.SpherePack()
>         ret.fromSimulation()
>         O.switchScene()
>         return ret
>
>
> O.materials.append(FrictMat(young=5e8,frictionAngle=.6,poisson=.3,density=1e7))
> sp = randomPeriPack(.01,.1*Vector3.Ones,10)
> sp.toSimulation()
> O.engines = [
>         ForceResetter(),
>
> InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=1.5,label='is2aabb')],allowBiggerThanPeriod=True),
>         InteractionLoop(
>
> [Ig2_Sphere_Sphere_ScGeom(interactionDetectionFactor=1.5,label='ss2d3dg')],
>                 [Ip2_FrictMat_FrictMat_FrictPhys()],
>                 [Law2_ScGeom_FrictPhys_CundallStrack()]),
>         NewtonIntegrator(damping=.2),
> ]
> O.dt = 0.0002
> #O.step()
> is2aabb.aabbEnlargeFactor = 1.
> ss2d3dg.interactionDetectionFactor = 1.
>
> dstrain = Matrix3(0,0,0,0,0,0,0,0,-0.002)
> trsf1 = O.cell.trsf
> I = Matrix3.Identity
> trsf2 = dstrain + I
> print(trsf2)
>
> O.cell.velGrad = dstrain/100/O.dt
>
> O.step()
> print(O.cell.trsf)
> O.step()
> print(O.cell.trsf)
>
> I think the second output should be (1,0,0,0,1,0,0,0,0.99998),
> but the second output is (1,0,0,0,1,0,0,0,0.99998) and the trsf starts to
> change in the next O.step()
> 1.What happend in the first O.step()?
> 2.If I use O.run(5), it only run 4 steps?
>
> Yours,
> Joe
>
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