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[Christian Jakob <question204526@xxxxxxxxxxxxxxxxxxxxx>]

New question #204526 on Yade:
https://answers.launchpad.net/yade/+question/204526

Hi,

I need to delete some particles inside my model and I dont know what is the best and physical/numerical correct way to do this.
If I say O.bodies.erase(id) it erases the body and the interactions will be erased in the next time step by InteractionLoop. But when I have capillary law active, I have to use neverErase flag as True to avoid a segmentation fault. So there are three options how to do this and I want to know what is the best option:


OPTION 1: only erase bodies
Because neverErase flag is True, interaction will still be active and can influence results, right? So if I later simulate increasing water level by deleting liquid bridges this remaining interactions from non-existant bodies can lead to instability, right?

O.bodies.erase(id)


OPTION 2: erase interactions manually first and erase bodies afterwards
To avoid the influence of interactions from non-existant bodies, one can erase the interactions before erasing the associated bodies. This normally leads to a segmentation fault. One can del with the segmantation fault by simply run 1 step after every erased body.

for i in O.bodies[id].intrs():
  O.interactions.erase(i.id1,i.id2)

O.bodies.erase(id)

O.run(1,True)


OPTION 3: deactivate capillary law, set neverErase=False, erase all interactions, delete bodies, set neverErase=True, activate capillary law again
I did not test this option, so I dont know if it works.

Law2_ScGeom_CapillaryPhys_Capillarity.dead=True
Law2_ScGeom_MindlinPhys_Mindlin.neverErase=False
O.interactions.clear()

O.bodies.erase(id)

Law2_ScGeom_MindlinPhys_Mindlin.neverErase=True
Law2_ScGeom_CapillaryPhys_Capillarity.dead=False


So what do you think  is the best option in this case? 


Christian

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