Equal masses on Couette flow

LAMMPS LAMMPS Beginners
1

Dear all,

In the couette flow code, all masses for the three types of atoms are equal.

Is there any particular reason for that?

Thanks

2

I can’t say for sure, because I did not write that code, but clearly its a system where all the atom types are exactly the same species:

mass		1 1.0
mass		2 1.0
mass		3 1.0

(...)

pair_coeff	* * 1.0 1.0 1.12246

but 3 different types of atoms are used to easily differentiate between the boundaries and the flow:

# define groups

region	     1 block INF INF INF 1.25 INF INF
group	     lower region 1
region	     2 block INF INF 8.75 INF INF INF
group	     upper region 2
group	     boundary union lower upper
group	     flow subtract all boundary

set	     group lower type 2
set	     group upper type 3

Its sometimes more practical to have 3 “LAMMPS” atom types instead of 1, even if 1 atom types would in principle be enough.

Simon

1 Like
3

It helps with visualization, too.