LIGGGHTS® - User Forum

Hello everyone,

I'm trying to pack rashig rings to create a packed bed reactor.
I don't know from where I have to start. I have an STL of the ring, I think I have to create a clump of that shape and then use the multisphere particle template. Is it right?
I'm not able to create the dump file from the STL, can anyone help me?

Any hint or suggestion is very helpful

Thanks

Hi all,

As we all know, neighbor cutoff = force cutoff+skin. However, I don't know how LIGGGHTS determines the force cutoff value.

Are there any command in LIGGGHTS that we could use to modify force cutoff (haven't found anyone yet)?

Best regards,

Su

Hi,guys

I want to calculate the average contactarea between particles,below is my command:

compute area particle pair/gran/local contactArea
variable avearea equal ave(c_area)
thermo_style custom step atoms ke v_avearea

but, it pointed out that mismatched compute in variable formula.........

I don't know why , who can tell me ?

thanks

hi,

if I use the command

variable zero equal 0
variable an equal -0.1
fix movement all move/mesh mesh mole linear/variable v_zero v_zero v_an
run 10000

and try to change now the vertical velocity to

variable an equal -10

the velocity to the mesh is set positiv doesnt mind if I set it to 10 or -10.
To test it just create a mesh and do

variable zero equal 0
variable an equal -0.1
fix movement all move/mesh mesh mole linear/variable v_zero v_zero v_an
run 10000
variable an equal -10

Hi all,

When unfixing a move wiggle fixed for a substrate made of particles, the kinetic energy of these particles wouldn't go to zero unless zeroing velocity by hand, i.e., by using "velocity group zero linear". Any idea?

Selim,

Hi all,

I am trying to understand the 6 components of stress tensor computed by stress/atom.
What are the physical meaning of kinetic energy contribution, angle, dihedral and improper component of the stress tensor?

What should be the keyword listed if I want to compute the stress tensor of a particle packing (sand foundation) under the gravitational force field?

Many thanks

Hi,

I'm trying to understand the values that are calculated with:

dump custom fx fy fz
compute pair/gran/local force
compute stress/atom

therefor I insert 2 particles, but just one particle is integrated. One particle lies on top of the other and gravity loading is on both of them acting.

Dear all,

I have a question about "rotate" command in LIGGGHTS.

The geometry in my work consists of two separate parts. The first one is rotating around a specific axis and the second one is rotating around the first geometry part.
For the first part, there is no problem but how can I simulate rotation of the second geometry part around the first which rotates itself?

Regards,
Shahab

Hello All,

I want to read multiple input data files using read_data command in my simulation. How can i do this?
These data files correspond to different parts of my geometry.

Can someone please help me on this.

Thanks,

Narendra

Hi all,

I am trying to create a single ellipsoid particle to do some comparison with a spherical particle but I have got the following error message:

"ERROR: Fix wall/gran (id zwalls1): requires atom attributes radius, omega, torque (../fix_wall_gran.cpp:88)"

I looked at "fix wall/gran command" & "set command" but I could not find where should I define these a attributes. Could some one please give me some hints about this and how to set the commands associated with ellipsoid style correctly.

Many thanks,

Leader