Differences between versions?

Submitted by mkoester on Thu, 08/19/2010 - 18:52

Hi Everybody,

It's been a while since my last update of Liggghts because of labwork and holydays, but yeesterday I updated my LIGGGHTS from 1.03 to 1.16 and made minor changes in my simulation (adding a dump for wall-stress).

However my results now look totaly different than what they looked like in 1.03 (see videos: www.yrthy.de/1_16.avi and www.yrthy.de/1_03.avi). It seems that the particles lost their cohesion.

Did I overread something in the changelogs or is there something wrong?

Thanks for your help,
Martin

Forums:

ckloss's picture

ckloss | Thu, 08/19/2010 - 19:31

Hi Martin,

there has been a bugfix in the cohesion model in 1.1.6 regarding the calculation of the contacting surface area.

This is mentioned in the version history - to keep track of such bugfixes and model improvements/changes, automated testloops will be run from now on to make the differences between versions visible.

Best,
Christoph

==============================
Fixed two issues with the cohesion model - there was a bug in calculating the contact area. Also added a check to ensure the model is only used for 3d simulation. Thanks to George Marketos (Imperial College London) for calling attention to this.

As of version 1.1.6 a quality assurance check will be done by running automated testloops comparing various thermo outputs (e.g. energy) over time that are generated by different versions. Please see this page for details.
==============================

Best regards,
Christoph

QuinnReynolds | Fri, 09/10/2010 - 13:15

Hi Martin/Christoph,

I have just compiled LIGGGHTS 1.1.6, and when I run the two example scripts in the "cohesion" folder, the results look virtually identical (i.e. cohesion does not seem to be calculated in either case). Could this be related to the change in the cohesion calculation code, or is it a bug/problem on my system?

Kind regards,
Quinn

ckloss's picture

ckloss | Fri, 09/10/2010 - 14:09

Hi Quinn,

>>Could this be related to the change in the cohesion calculation code
Yes. But cohesion is calculated - if you look at the energy levels in both simulations, you will differences here due to the cohesion model. I will change the example in the next release so that the cohesion energy density value makes for a more visible comparison

Christoph