The NewtonIntegrator does not apply angular motion for aspherical bodies

Bug #1832235 reported by kaiset on 2019-06-10
10
This bug affects 2 people
Affects Status Importance Assigned to Milestone
Yade
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Bug Description

I've tried several ways to impose an initial angular velocity on a free polyhedron but they do not work well as commented in the script and below. Please help me with this. Thanks!
Here are things I've observed: [In the code below, I simulate 2 polyhedrons, poly1 is free and has an initial velocity while poly2 is fixed.]
If I directly use state.angVel or utils.setBodyAngularVelocity to impost an angular velocity on both polyhedrons, nothing happens to poly1, I could observe no rotation but just transnational move. However, I could observe rotation on poly2, which is fixed.

A work around is to use angMom.

## using: "b.state.angMom"
Mom=b1.state.ori*b1.state.inertia # This results to angVel=Vector3(1,1,1).
# Modify accordingly, to modify a specific angular velocity. e.g., to get an initial angVel=Vector3(5,6,7)
Mom[0]=Mom[0]*5.
Mom[1]=Mom[1]*6.
Mom[2]=Mom[2]*7.

O.bodies[0].state.angMom=Mom

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
# ENGINES
# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #

O.engines=[
 ForceResetter(),
 InsertionSortCollider([Bo1_Polyhedra_Aabb()],verletDist=0.01),
 InteractionLoop(
  [Ig2_Polyhedra_Polyhedra_PolyhedraGeom()],
  [Ip2_PolyhedraMat_PolyhedraMat_PolyhedraPhys()],
  [Law2_PolyhedraGeom_PolyhedraPhys_Volumetric()]
 ),
 NewtonIntegrator(damping=0.0,exactAsphericalRot=True,gravity=[0,0,0]),
]

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
# POLYHEDRAL PARTICLES
# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #

from yade import polyhedra_utils
m = PolyhedraMat()
m.density = 2000 #kg/m^3
m.young = 150e6 #Pa
m.poisson = .4
m.frictionAngle = 3.0 #rad

edge=0.025
vertices=[(-edge, -edge, -edge),
          (-edge, edge, -edge),
   ( edge, -edge, -edge),
   ( edge, edge, -edge),
   (-edge, -edge, edge),
          (-edge, edge, edge),
   ( edge, -edge, edge),
   ( edge, edge, edge)]

# Free
b1 = polyhedra_utils.polyhedra(m,v=vertices)
b1.state.pos = (0,0,0)
O.bodies.append(b1)

# Fixed
b2 = polyhedra_utils.polyhedra(m,v=vertices,fixed=True)
b2.state.pos = (4.*edge,0,0)
O.bodies.append(b2)

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
# INITIAL VELOCITY
# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #

# Initial translational velocity
O.bodies[0].state.vel=Vector3(1,0,0)

# Initial angular velocity
# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
##Directly assigning the angular velocity- Not imposing initial angular velocity- No rotation for the free one but the fixed one will rotate
#O.bodies[0].state.angVel=Vector3(1,1,0)
#O.bodies[1].state.angVel=Vector3(1,1,0)

## using: "utils.setBodyAngularVelocity" - Not working for non-fixed bodies(poly1) but working for poly2
utils.setBodyAngularVelocity(0,5*Vector3(1,1,1))
utils.setBodyAngularVelocity(1,5*Vector3(1,1,1))
# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #

from yade import qt
v=qt.View()

O.dt=1.0e-8

O.saveTmp()

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