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[liucheng83 <question210805@xxxxxxxxxxxxxxxxxxxxx>]

Question #210805 on Yade changed:
https://answers.launchpad.net/yade/+question/210805

Description changed to:
Hi, all
I want to add RadialForceEngine to one particle with ids=pmove (id=3) to overcome the gravity effect, but when I define the RadialForceEngine  with ids=pmove, the particle is gone away, and form inspection, its velocity is nan, why? Here is the code,
anybody can give me some advice, thank you!
-----------------------------------------------------------------
# -*- coding: utf-8 -*-
# encoding: utf-8
from yade import utils, ymport, qt, plot


# basic simulation showing sphere falling ball gravity,
# bouncing against another sphere representing the support

interactionRadius=1.5
iterPeriod_checkInteraction=1000

# DATA COMPONENTS

O.materials.append(FrictMat(young=8e6,poisson=0.3,frictionAngle=radians(20),density=2700,label='spheres'))
# add 2 particles to the simulation
# they the default material (utils.defaultMat)
O.bodies.append([
	# fixed: particle's position in space will not change (support)
	utils.sphere(center=(0,0,0),radius=.5,fixed=True),
	utils.sphere(center=(0,3,0),radius=.5,fixed=True),
	# this particles is free, subject to dynamics
	utils.sphere((0,0,5),.5),
	#utils.sphere((0,3,20),.5)
])

pmove=O.bodies.append([utils.sphere((0,3,5),.5)
])

# FUNCTIONAL COMPONENTS

# simulation loop -- see presentation for the explanation
O.engines=[
	ForceResetter(),
	InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=interactionRadius,label='aabb')]),
	InteractionLoop(
		[Ig2_Sphere_Sphere_ScGeom(interactionDetectionFactor=interactionRadius,label='Ig2ssGeom')],
		[Ip2_FrictMat_FrictMat_FrictPhys()],
		[Law2_ScGeom_FrictPhys_CundallStrack()]
	),
	# apply gravity force to particles
	#GravityEngine is deprecated
	#GravityEngine(gravity=(0,0,-9.81)),
	RadialForceEngine(ids=pmove,axisDir=(0,0,1),axisPt=(0,3,5),fNorm=O.bodies[3].state.mass*9.81*0.5,label="radialForce"),
	# damping: numerical dissipation of energy
	NewtonIntegrator(damping=0.1,gravity=(0,0,-9.81)),
	PyRunner(command='checkInteraction()',iterPeriod=iterPeriod_checkInteraction,label='checker')
]

# set timestep to a fraction of the critical timestep
# the fraction is very small, so that the simulation is not too fast
# and the motion can be observed
O.dt=.5e-4*utils.PWaveTimeStep()


#### to see it
v=qt.Controller()
v=qt.View()
rr=qt.Renderer()
rr.intrAllWire=True


# save the simulation, so that it can be reloaded later, for experimentation

def checkInteraction():
	print O.iter
#	if O.interactions[3,1].isReal:
#		i=O.interactions[3,1]
#		print O.iter
#	else:
#		print O.iter


#run one single step
O.step()
#### initializes now the interaction detection factor
#
#aabb.aabbEnlargeFactor=-1.
#Ig2ssGeom.interactionDetectionFactor=-1.
O.saveTmp()

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