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Error InsertionSortCollider

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asked Apr 7 by alanbds (140 points)

Hi,

 

I having this ERROR in my simulation. 

It happens between the suballast (smaller spheres) and ballast. The suballast is generated and compressed, them, it should start to generate but the error shows up. I tried to increase and also decrese the dtSafety, but none of them worked.

1 Answer

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answered Apr 8 by eudoxos (46,550 points)

Hi Alan,

the error means there is some particle which is moving way too fast (traversing longe distance within single timestep), meaning it is exploding (numerically unstable).

Three things you can try:

  1. Make sure there are no sudden particle overlaps (such as that you load new particles and place them over those which exist already), this creates enormous (unrealistic) contact force shooting the particles away from each other with nonsensical acceleration and speed.
  2. decrease S.dtSafety (to something like 0.1 or even less, just to try), see if it helps. Critical timestep is computed automatically by the DynDt engine but depending among other on the contact model, the result might not be completely safe and is multiplied by dtSafety. Especially with viscous models, stiffness might increase considerably due to high contact force. This is only a temporary solution to try.
  3. If you succeed with decreasing dtSafety, try putting it back (to perhaps 0.7) and run DynDt more often by saying: S.dynDt.stepPeriod=10 or even 1. See again if that helps. DynDt usually runs every 100 steps, but if conditions change abruptly (e.g. adding particles which are much smaller than those which have been in the simulation before), it will take a few timesteps before dt is adjusted, resulting in explosion.
  4. Increase S.lab.collider.maxSortPass to something well over 20, maybe 100. But I doubt this will really help, something is moving way too fast.

Good luck,

Vaclav

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