How to compute tangential forces at contact for gran/hertz/history pair style

Submitted by Jing Lu on Fri, 05/22/2015 - 11:03

Hi all,

I'm using 'gran/hertz/history' for pair_style and 'compute pair/gran/local history' to output tangential force, because I thought 'history' in 'compute pair/gran/local' means the 3 components of tangential force in xyz (i.e. ft1,ft2,ft3). However the results are extremely small.

I have tried 'compute pair/local ... p1 p2 p3 p4' but it is said improper for gran/hertz/history (I think it was changed from original lammps).

I found in another post where Christopher said 'history' means 'elongation of the tangential spring'. So does it mean that 'history' has the unit of length? If so, how can I output kt for each pair as it is related to particle sizes and normal overlapping at contact? How can I properly output the tangential force for each pair?

Thanks,
Jing

Forums:

ckloss's picture

ckloss | Mon, 06/01/2015 - 12:56

Hi Jing,

compute pair/gran/local will be updated in the next release to output normal and tangential force separately (However, you can already calculate them because the positions of particles i and j can be output). For tangential/history, "history" will output the elogation of the tangential spring

Christoph

Jing Lu | Mon, 06/01/2015 - 17:53

Hi Christoph,

Thanks for your reply. I will try your suggestion. Looking forward to the new release.

Jing