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[Paolo <question688508@xxxxxxxxxxxxxxxxxxxxx>]

Question #688508 on Yade changed:
https://answers.launchpad.net/yade/+question/688508

Paolo gave more information on the question:
Thank you Jan and Bruno for the hint about the NewtonIntegrator. It works. However I cannot make the top stop at a desired height. In particular I have a box which is 20 in height. I want the top to stop when it reaches 15 (so it goes down only for 5). I paste here the modified code (I made some changes from the previous code by looking at the oedometric example in the Yade Manual).
Basically I would like to reproduce the following steps:

     1. Generation of the packing from a cloud.
     2. Once the pack is stable (i.e. unbalancedforce<0.1) generation of the top (plate) which goes down.
     3. Stop the plate at 15 height.
     4. Reverse the gravity.
     5. Wait the new equilibrium configuration ( i.e. unbalancedforce<0.1) and stop the simulation.

Then I need to reproduce 4 and 5 many times in order to simulate the
shaking but I think that this could be easy to handle.

Here is the modified code.

# import yade modules that we will use below
from yade import pack, plot

#Materials
fr = 0.455;rho=2650.0
global vel
vel=2

Mat1 = O.materials.append(ViscElMat(kn=10.0e4,ks=10.0e4,frictionAngle=fr,density=rho))
Mat2 = O.materials.append(ViscElMat(kn=10.0e4,ks=10.0e4,frictionAngle=fr,density=rho))

# create rectangular box from facets
box=O.bodies.append(geom.facetBox((5,5,10),(5,5,10),wallMask=15,material=Mat1))
ground=O.bodies.append(utils.wall(position=(0,0,0),axis=2,sense=0,material=Mat1))

# create empty sphere packing
sp=pack.SpherePack()

# generate spheres

sp.makeCloud((0,0,0),(10,10,20),rMean=0.5)

# add the sphere pack to the simulation
sp.toSimulation(material=Mat2)

O.engines=[
		ForceResetter(),
  		InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb(),Bo1_Wall_Aabb()]),
   		InteractionLoop(
     	        # handle sphere+sphere and facet+sphere collisions
      		[Ig2_Sphere_Sphere_ScGeom(),Ig2_Facet_Sphere_ScGeom(),Ig2_Wall_Sphere_ScGeom()],
      		[Ip2_FrictMat_FrictMat_FrictPhys()],
      		[Law2_ScGeom_FrictPhys_CundallStrack()]
   			       ),
		NewtonIntegrator(gravity=(0,0,-9.81),damping=0.0,label='integrator'),

		# call the checkUnbalanced function (defined below) every 2 seconds
		PyRunner(command='deposition()',realPeriod=2,label='checker'),
		# call the addPlotData function every 200 steps
		PyRunner(command='addPlotData()',iterPeriod=100),
 	 ]

O.dt=.5*PWaveTimeStep()

def deposition():
	if O.iter<100: return 
	if unbalancedForce()>0.1: return 
	O.bodies.append(utils.wall(position=(0,0,20),axis=2,sense=0,material=Mat1))
	global plate       
	plate=O.bodies[-1] 
	plate.state.vel=(0,0,-vel)
	checker.command='stopPlate()'

def stopPlate():
	if plate.state.pos[2]<15: 
 		plate.state.vel*=0
	integrator.gravity=(0,0,+9.81)	
	checker.command='stop1()'

def stop1():
	if unbalancedForce()<.02: 
		O.pause()
		

def addPlotData():
   plot.addData(i=O.iter,UnbalancedForce=unbalancedForce(),Porosity=porosity()*100,Density=(1-porosity())*100,
)

plot.plots={'i':('UnbalancedForce',None,'Porosity','Density',
)}


plot.plot()

O.saveTmp()
 

Thank you guys!! =)

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