Hello LIGGGHTS forum, I am trying to run a simulation in an inclined surface. Till now my script is working nicely.
I want to add viscous and damp command in my script.
When ever I added it as ` fix 1 viscous 0.1 ` or `fix 1 damp viscous 0.5 scale 3 2.5` I got following message.
```
ERROR: Could not find fix group ID
```
I also tried to add as `fix m6 viscous...` got the same error.
How do I add them correctly?
Any help would be appreciated.
Thanks a lot.
My script
```
# Initialize
atom_style granular
atom_modify map array
###########################################################################################
#Describe boundary
boundary f f f
newton off
communicate single vel yes
units si
####################################################################################################################
#Declare domain number of materials as domain
region domain block -0.5 0.1 -0.2 0.2 -0.4 0.15 units box
create_box 1 domain
#####################################################################################################################
#Neighbor listing
neighbor 0.001 bin
neigh_modify delay 0
#####################################################################################################################
## Material and interaction properties
fix m1 all property/global youngsModulus peratomtype 5.e6
fix m2 all property/global poissonsRatio peratomtype 0.4
fix m3 all property/global coefficientRestitution peratomtypepair 1 0.6
fix m4 all property/global coefficientFriction peratomtypepair 1 0.4
fix m5 all property/global k_finnie peratomtypepair 1 1.0
fix m6 all property/global coefficientRollingFriction peratomtypepair 1 0.02
#fix m7 viscous 0.1
#######################################################################################################################
#New pair style, define physics
pair_style gran model hertz tangential history #Hertzian without cohesio
pair_coeff * *
#############################################################################################
#Time step
timestep 0.00001
##############################################################################################
# Integrator and gravity
fix integrate all nve/sphere
#fix damp nve_group viscous 0.189
fix gravi all gravity 9.81 vector 0.0 0.0 -1.0
#############################################################################################
#Particle insertion
#fix cad all mesh/surface/stress file meshes/plane.stl type 1 wear finnie
#fix cad all mesh/surface/stress file meshes/simple_chute.stl type 1 wear finnie
fix cad all mesh/surface/stress file meshes/down.stl type 1 wear finnie
fix inface all mesh/surface file meshes/insertion_face.stl type 1
fix granwalls all wall/gran model hertz tangential history mesh n_meshes 1 meshes cad
fix mass all massflow/mesh mesh inface count once point_at_outlet 0. 0. 0.
#######################################################################################################
# Particle properties
fix pts1 all particletemplate/sphere 15485863 atom_type 1 density constant 2500 radius constant 0.01
#Describe the composition of the particle distribution
fix pdd1 all particledistribution/discrete 32452843 1 pts1 1.0
##############################################################################################################
#Define insertion region, velocity for particle
group nve_group region domain
region bc cylinder z 0.0 0.0 0.015 0.05 0.12 units box
#fix 1 all nve velocity all pts1 NULL 0.5 NULL units box
##############################################################################################################
#particle insertion
fix ins nve_group insert/pack seed 32452867 distributiontemplate pdd1 insert_every 1 overlapcheck yes all_in yes particles_in_region 1 region bc
################################################################################################################
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
```
Daniel Queteschiner | Mon, 05/03/2021 - 09:58
atom group
See my answer in the CFDEMcoupling section
PS: Please, don't double post ...
laudari | Thu, 05/06/2021 - 16:50
Apologies for the repeated test and thank you for reply
HI @Daniel , thank you so much for your answer.
Apologies for the repeated test.
One more question,
When i run simulation sometimes my particles are colliding to each other.
Is there any command to stop collision?
Thank you
mschramm | Thu, 05/06/2021 - 19:13
neigh_modify command
To exclude an atom type interaction, see the exclude flag in neigh_modify.
https://www.cfdem.com/media/DEM/docu/neigh_modify.html
laudari | Sun, 05/09/2021 - 11:45
I used exclude command,
Thank you so much. I solved the problem with exclude command.