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[Nolan Dyck <question237047@xxxxxxxxxxxxxxxxxxxxx>]

New question #237047 on Yade:
https://answers.launchpad.net/yade/+question/237047

Ok so I have recently looked into the Bubble Materials again, and made some improvements to the BubbleMat files (.hpp) and (.cpp). I have pushed the changes to my fork of yade: https://github.com/ndyck/trunk

There seems to be some issues when I run the following script (bouncingsphere.py) for bubble collisions using the new code:

rad = 5e-3
#O.materials.append(FrictMat(young=1e2,density=1000))
O.materials.append(BubbleMat(density=10))
O.bodies.append([
   utils.sphere(center=(0,0,0),radius=rad,fixed=True),
   utils.sphere((0,0,2*rad*1.2),rad)
])
O.dt = 1e-6

O.engines=[
   ForceResetter(),
   InsertionSortCollider([Bo1_Sphere_Aabb()]),
   InteractionLoop([Ig2_Sphere_Sphere_ScGeom()],[Ip2_BubbleMat_BubbleMat_BubblePhys()],[Law2_ScGeom_BubblePhys_Bubble(surfaceTension=0.035)]),
#   InteractionLoop([Ig2_Sphere_Sphere_ScGeom()],[Ip2_FrictMat_FrictMat_FrictPhys()],[Law2_ScGeom_FrictPhys_CundallStrack()]),
   NewtonIntegrator(damping=0.1,gravity=(0,0,-9.81e-3))
]

The bubble bounces a couple of times (apparently depending on size, gravity scale, and density) and then disappears. The inspector shows the normal forces and penetrationDepth going to NaN. If the bubble code is commented out and the CundallStrack code is uncommented, there seems to be no trouble with this no matter how small I make the particles or how I vary the timestep size or other parameters.

I do not think this has to do with the time step size as I have played around with it a lot and it doesn't seem to have any effect on whether the contact breaks the solution, so I don't think I'm exceeding the critical timestep size or anything.

It would also be nice to know how to update my fork to the changes made in yade/trunk. I do not understand how to do that. This may be part of the issue.

Thanks in advance,
Nolan

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