Conservation of Energy after impact

Submitted by antoniosereno on Fri, 11/15/2019 - 17:55

Hi everyone.
I am working on a simulation that involves several impacts between particles; to gain a better understanding of the impact phenomenom I simulated a single impact between 2 particles and I noticed that although the friction coefficient was put to 0 and the coefficient restitution to 1, the conservation of energy and linear momentum was not respected.
Can I ask why? Is it related to the mechanism that the software uses to compute the contact forces or there may be some conceptual mistake I've made?
Thank you for your help

Forums:

nasato | Mon, 11/18/2019 - 13:39

Hi,

Did you try to set LimitForce on?

https://www.cfdem.com/media/DEM/docu/gran_model_hertz.html
limitForce values = 'on' or 'off'
on = ensures that the normal force is never attractive (an artefact that can occur at the end of a collision).
off = standard implementation that might lead to attractive forces.

Best, Nasato

mschramm | Mon, 11/18/2019 - 17:51

Hello,
Using the script that is provided in the other thread and setting the friction to 0.0
Total kinetic energy before collision 2.7001989e8
Total kinetic energy after collision 2.7001671e8
That is a percent error of 0.0012% This can be easily explained by numerical errors (rounding and integration).