Using eDPD package there is a difference in where we choose to heat and temperature profile. Can anybody help me figure this out?

[nema9210]

Dear All,

I have sent this to the author of the eDPD package as well, but I just wanted to post it here too.Maybe some one can help. Looking at the following code:

units lj
dimension 3
boundary p p p
neighbor 0.2 bin
neigh_modify every 1 delay 0 check yes

atom_style edpd

region edpd block -5 5 -5 5 -3 3 units box
create_box 1 edpd
create_atoms 1 random 1600 276438 NULL
mass 1 1.0
set atom * edpd/temp 1.0
set atom * edpd/cv 1.0E5

pair_style edpd 1.58 9872598

pair_coeff 1 1 18.75 4.5 0.41 1.58 1.41E-5 2.0 1.58

compute mythermo all temp
thermo 100
thermo_modify temp mythermo
thermo_modify flush yes

comm_modify vel yes

velocity all create 1.0 432982 loop local dist gaussian

fix mvv all mvv/edpd 0.5
fix upper all edpd/source cuboid 0.0 2.5 0.0 10.0 5.0 6.0 0.01
fix lower all edpd/source cuboid 0.0 -2.5 0.0 10.0 5.0 6.0 -0.01

timestep 0.01
run 500
reset_timestep 0

compute temp all edpd/temp/atom
compute ccT all chunk/atom bin/1d y 0.0 1.0
fix stat all ave/chunk 1 500 500 ccT c_temp density/number norm sample file t2.profile

run 500

you can see that I am choosing the
upper heat source to be a cube with coordinates (x=0:10, y=2.5:7.5, z=0:6) ,
lower cooling source to be a cube with coordinates (x=0:10, y=-2.5:2.5, z=0:6),
and my box region is: (x=-5:5 ,y=-5:5, z= -3,3)

drawing it in mathematica

The yellow cube is the heating region, so I would expect to have higher temperature in the left and right side of the box and a cooler region in the middle, but looking at the temperature plot:

we can see that the middle of right half is heating (have higher temperature) and the middle of left half is cooling. Can anybody help me understanding what is going on?

Regards,
Delaram

[nema9210]

The author replied to my question:

The edpd/source cuboid takes the cuboid center (Cx, Cy, Cz) and length in each direction (Lx, Ly, Lz) to define the geometry,

fix upper all edpd/source cuboid 0.0 2.5 0.0 10.0 5.0 6.0 0.01

will add a heat source of Q=0.01 in the following region

x = -5:5

y = 0:5

z = -3:3

fix lower all edpd/source cuboid 0.0 -2.5 0.0 10.0 5.0 6.0 -0.01

will add a heat sink of Q=-0.01 in the following region

x = -5:5

y = -5:0

z = -3:3.

In LAMMPS documentation it said

https://docs.lammps.org/fix_dpd_source.html

cuboid values = cx,cy,cz,dLx,dLy,dLz,source
cx,cy,cz = x,y,z lower left corner of a cuboid domain (distance units)
dLx,dLy,dLz = x,y,z side length of a cuboid domain (distance units)
source = heat source or concentration source (flux units, see below)

which is wrong.

cx,cy,cz = x,y,z should be the Center of a cuboid domain (distance units)

[akohlmey]

Thanks for reporting back. We’ll update the documentation soon.

[nema9210]

Thank you

[akohlmey]

I am also looking to add a new keyword “region” that would allow to define heat sources via LAMMPS’ region command and thus much more flexibility and consistency in how to add and apply those regions.

[nema9210]

That would be great. Thanks a lot.

Regards,
Delaram