Difference between force on atoms and force calculated by contact

Submitted by fabregas04 on Mon, 09/13/2021 - 11:16

Hi, I have a question about the value of the force and how it come from.

I did the simulation and dumped the file for contact and atom.

I get the atom data using 'dump aa all custom time id type x y z vx vy vz fx fy fz ...'

And the contact data using 'compute bb all pair/gran/local id pos force_normal' and dump it.

The atom force will be the sum of all forces acting on the atom. Also, I know that the force calculated by contact is using the formula in the link below.
(https://www.cfdem.com/media/DEM/docu/gran_model_hertz.html)

But when I compare the forces with the data, atom force doesn't look like sum of all forces on atom.

Is there something wrong with my assumptions for this?

Or anyone with the idea of obtaining atom force, please let me know.