non-sphere particles

Hi SHG,

what you typically do when using fix rigid is to set up the single particles in the simulation that should lateron be part of the non-spherical ones, attach different molecule IDs to it and then use the fix riid command to "glue" the different particles together

Best wishes
Christoph

Hi SHG,

this is the code I used to model this system (each beer bottle is a single rigid body):
https://www.youtube.com/watch?v=W_bRl4wmkY8

###############################################################################################################
#Idea: read same coordinates from file and than move initial position to start position
#needs 3*i files with IDs consecutive from 0..maxID*i*3
#
variable i loop 1 10 #loop counter (max 10, bc only 31 groups are allowed and every loop inserts 3 bottles)
variable p equal 1 #counter for prototype-file
region bottle_in cylinder z 0 0 0.0146 -0.001 0.15 #catch all atoms in insert region
#
label loop
variable xnew atom x+$L*$i
read_data bottle$p.prototype add #bottle in 0/0/0
group bottle$p region bottle_in #assign group1
variable ynew atom y+$L #new y-position
set group bottle$p x v_xnew y v_ynew #shift right
variable p equal $p+1 #next prototype
#
read_data bottle$p.prototype add #bottle in 0/0/0
group bottle$p region bottle_in #assign group2
variable ynew atom y-$L #new y-position
set group bottle$p x v_xnew y v_ynew #shift left
variable p equal $p+1 #next prototype
#
read_data bottle$p.prototype add #bottle in 0/0/0
group bottle$p region bottle_in #assign group3
set group bottle$p x v_xnew #do not shift in y direction
variable p equal $p+1 #next prototype
#
next i
jump SELF loop
#
################################################################################################################
#gravity and integreator for rigid body
fix gravi all gravity 9.81 vector 0.0 0.0 -1.0
fix integr all rigid group 30 bottle1 bottle2 bottle3 bottle4 bottle5 bottle6 bottle7 bottle8 bottle9 bottle10 &
bottle11 bottle12 bottle13 bottle14 bottle15 bottle16 bottle17 bottle18 bottle19 bottle20 &
bottle21 bottle22 bottle23 bottle24 bottle25 bottle26 bottle27 bottle28 bottle29 bottle30

This approach is limited to 31 rigid bodies, because you can not make more than 32 groups.

With a little hack in atom_vec_sphere (where the atom style gran is defined) to store & communicate the molecule id too you can assign a molecule ID to every particle and than use fix rigid based on mol-id's instead of groups. (I think this would be possible with a hybrid granular molecure style, but than the read_data files needs to have the mol id included, I did not test this)

variable i loop 1 16 #loop counter (every loop inserts 3 bottles)
variable p equal 1 #counter for prototype-file
region bottle_in cylinder z 0 0 0.0146 -0.001 0.15 #catch all atoms in insert region
#
label loop
variable xnew atom x+$L*$i
read_data bottle$p.prototype add #bottle in 0/0/0
#group bottle$p region bottle_in #assign group1
variable ynew atom y+$L #new y-position
set region bottle_in mol $p
set region bottle_in x v_xnew y v_ynew #shift right
variable p equal $p+1 #next prototype
#
read_data bottle$p.prototype add #bottle in 0/0/0
#group bottle$p region bottle_in #assign group2
variable ynew atom y-$L #new y-position
set region bottle_in mol $p
set region bottle_in x v_xnew y v_ynew #shift left
variable p equal $p+1 #next prototype
#
read_data bottle$p.prototype add #bottle in 0/0/0
#group bottle$p region bottle_in #assign group3
set region bottle_in mol $p
set region bottle_in x v_xnew #do not shift in y direction
variable p equal $p+1 #next prototype
next i
jump SELF loop
#
################################################################################################################
#gravity and integreator for rigid body
fix gravi all gravity 9.81 vector 0.0 0.0 -1.0
neigh_modify exclude molecule all #exclude if both atoms are in the same molecule and in the same group (speeds up simulation by factor 4!)
fix integr all rigid molecule #needs hacked atom_vec_sphere.cpp


Cheers,
Christian.

http://www.richtisoft.de/impress.php