Inconsistency between the two methods calculating wall-particle total force

Dear all,

Good morning.

In my case, a mesh (plane, generated by gmesh) wall push the particle bed. However, I find the inconsistency of the total contact force on the wall by using two methods:

A) 1) fix wallleft all mesh/surface/stress; 2) variable fwlx equal f_wallleft[1]; 3) export it into the csv file
B) 1) compute cpw all wall/gran/local id pos force; 2) dump all components of cpw; 3) sum all forces in excel

The force by mesh/surface/stress is much different with the one by compute/wall/gran/local.

I do not know why it happens and which one I should use to get the real total contact force on the wall. Are there any suggestions?

Looking forward to your kind help. Thank you very much.

Best regards,
Solient