particles cross wall

Submitted by sajjadjeeven on Wed, 07/14/2010 - 21:04

hi all ! i am new comer in liggghts. i made a box and then divided it into two parts by importing an mesh wall(STl file).
I poured the particles on one side of the box. When i applied wiggle command the particles penetrate into the imported wall and cross it. i want the partcles should not cross the wall. there is my input file. If anybody help me i will be thankful.
sajjad

# Wall import from CAD

atom_style granular
boundary f f f
newton off
atom_modify sort 0 0

communicate single vel yes
units si

region reg block -0.01 0.51 -0.01 0.25 -0.01 1.31 units box
create_box 1 reg
region sim block 0 0.25 0 0.25 0. 1.31 units box

neighbor 0.002 bin
neigh_modify delay 0

#Material properties required for new pair styles

fix m1 all property/global youngsModulus peratomtype 5.e6
fix m2 all property/global poissonsRatio peratomtype 0.45
fix m3 all property/global coefficientRestitution peratomtypepair 1 0.7
fix m4 all property/global coefficientFriction peratomtypepair 1 0.05
fix m5 all property/global characteristicVelocity scalar 2.
#New pair style
pair_style gran/hertz/history 1 0 #Hooke without cohesion

pair_coeff * *

timestep 0.00005

fix 1 all nve/sphere
fix 2 all gravity 9.81 vector 0.0 0.0 -1.0
fix boxwalls_x all wall/gran/hertz/history 1 0 xplane 0 0.51 1

fix boxwalls_y all wall/gran/hertz/history 1 0 yplane 0 0.25 1
fix boxwalls_z all wall/gran/hertz/history 1 0 zplane 0 1.31 1

#
#import triangular mesh from cad; the syntax is as follows:
#"fix customname all mesh/gran stl_filename wall_type scale_factor x_off y_off z_off"

fix cad all mesh/gran sa20.stl 1 0.1014 -8.917 1.19 7.505 90. 90. 0.

#use the imported mesh as granular wall

fix granwalls all wall/gran/hertz/history 1 0 mesh/gran 1 cad
#region of insertion

#above surface, no contact
#region bc block 0.001 0.0225 0.0035 0.0225 0.0085 0.120 units box
region bc block 0.001 0.215 0.001 0.215 0.005 0.080 units box
group grp region sim
#group nve_group region reg

fix ins grp pour 55 1 17985583 region bc vol 0.6 100 diam uniform 0.03 0.03 dens uniform 2500 2500 vel uniform 0. 0. 0. 0. -0.3

compute 1 all erotate/sphere
thermo_style custom step atoms ke c_1 vol
thermo 1000
thermo_modify lost ignore norm no
compute_modify thermo_temp dynamic yes

dump dumpstl all stl 50 dump.stl

#insert the first particles so that dump is not empty4
run 1
dump dmp all custom 50 dump20.meshGran id type type x y z ix iy iz vx vy vz fx fy fz omegax omegay omegaz radius

#one geometry dump is enough
undump dumpstl

#insert particles
run 50000 upto
write_restart rest.20

ckloss's picture

ckloss | Wed, 07/14/2010 - 21:12

Hi,

as already posted: are you using the most current version? There has been a change in LIGGGHTS 1.1.5 that might be related to that.

Also, it might be that the time-step is too high so that mesh change is so rapid that particles are instantaniously in the other box, check if v_wall*dt<0.01*dp, where dp is the smallest particle diameter

One more comment: Are you using 2 wall layers or just one? Because if you are using only one layer, particles may overlap the wall from both sides so they can still interact with each other

Best,
Christoph

sajjadjeeven | Thu, 07/15/2010 - 17:46

Dear Christoph!
First of all i am thankful to you for your,s reply.
i downloaded the new version of liggghts 1.1.5
i decreased the time step to 0.000005 to ensure that v_wall*dt<<0.01*dp
i also used the two adjacent walls in the center of container but the problem is still there that when i apply wiggle command the particles penetrate the wall and cross it.
sajjadl

sajjadjeeven | Fri, 07/16/2010 - 16:15

Dear christoph!
i found that there was an error in my script. I removed it and run the script. now it is ok. If i feel some problem then i would like to take your,s time.THANKS for your,s positve response. I would also like to appreciate you for helping the peoples.
sajjad