How to move an ideal wall ?

Submitted by venes520 on Thu, 02/16/2012 - 10:50

I created ideal walls and want to use the fix wall/gran/hertz/history/stiffness command and the syntax of this command is:

fix ID group-ID wall/gran/(*) friction_damp_flag cohesionflag wallstyle args keyword values ...

I don't really understand the group-ID here, does it mean the ID of the group that I want to create walls to bound? or the ID for the group of the walls themselves? How to "group" these walls? they don't consist of particles.

also, if I want to freeze or move the wall, the freeze or move commands require input of group-ID, but how to define the group-ID for ideal walls?

Thank you very much
Anson

Forums:

moritzhoefert | Thu, 02/16/2012 - 12:08

Anson,

see the documentation of fix --> fix.html. group-ID is the group of atoms that are affected by the fix.

Regards,
Moritz

venes520 | Thu, 02/16/2012 - 12:33

Moritz,
Thanks for your reply.
by "group-ID is the group of atoms that are affected by the fix" does it mean the group of atoms which is to be bound by the wall that I am going to create?

If yes, then how to move this wall? because under the fix move command, I also need to input the group_ID, which one should I input?

If I input the same group_ID as the group_ID in the fix wall command, will this move command move the atoms in this group or the wall, or together?
I just want to move the wall, so that the wall can push that group of atoms.

Cheers
Anson Liang

raguelmoon's picture

raguelmoon | Thu, 02/23/2012 - 15:00

Hi,
I guess you need to import CAD into LIGGGHTS as a wall and then move it.
Best,
Ram

Ram

Philippe's picture

Philippe | Fri, 02/17/2012 - 08:39

Hello Anson,

using "all" as group name for these fixes is fine - the LAMMPS fix syntax requires a group-ID to be given for each fix, but as far as I know the group-ID has no effect in these fixes.

hope this was helpful
Philippe