Testing the Kevin-Helmhotz instability with USER-SPH package

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1

Hi,

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.

Quang

2

Greetings,

your script did not specify box boundary type so it used the default periodic boundary conditions as shown in the manual:

pastedImage.png

A few particles seem to be getting through the bottom edge and are being re-mapped to the top.