I am just playing around with LAMMPS - specifically the USER-SPH package. I am trying to create the Kevin-Helmhotz instability by having two flows in opposite direction with the SPH. The results is pretty close to what we should see (or so I hope), but if you can see at the top and bottom I have some particles somehow managed to penetrate the walls and get re-entried at the other end.
Video of the clip: https://goo.gl/ZsbMNF
In case the video clip is not clear enough, here is the phenomenom: https://goo.gl/eoxcya
Here is the script I used for this case: https://pastebin.com/grt1SJZc
Am I doing something wrong, even fundamentally?
Thanks in advance for your time.