Continuous Mixer Example

Submitted by StefanDekker on Thu, 07/21/2016 - 04:22

Hi everyone,

I am looking into LIGGGHTS to do some screw conveyor simulations and I have been trying to run the Continuous mixer examples from this site as a starting point.

I understand they where written in the older version of Liggghts, I have been modifying the input script with the updated syntax fro version 3. I have come up against problems regarding the mesh that is supplied in the example.

I get the following error when I try to run the script:

WARNING: It is heavily recommended to use 'neigh_modify delay 0' with granular pair styles (../pair_gran.cpp:223)
Setting up run ...
Mesh cad1: 785 elements have high aspect ratio (soft limit: smallest angle > 0.500000 ° required)
WARNING: Fix mesh: Mesh contains highly skewed element, moving mesh (if used) will not parallelize well (../surface_mesh_I.h:607)
Mesh cad1: 138 mesh elements have a really unreasonably high aspect ratio (hard limit: smallest angle must be > 0.057296 °)
ERROR on proc 0: Fix mesh: Bad mesh, cannot continue. You will need to fix or remove these element. Remedies:
- You can use the 'element_exclusion_list' feature to remove elements with too many neighbors and elements with angles below the hard limit
(../surface_mesh_I.h:633)

I have found a couple of other posts with similar problems and the common suggestion is to simplify the mesh. I have tried re meshing the .stl files in meshlab but I then get another error:

ERROR: Mesh error - root causes: (a) mesh empty or (b) dimensions too small - use different unit system (../multi_node_mesh_parallel_I.h:555)

Now I have not used meshlab before this so I am unsure on if I am doing it correctly. I used the process: Filters > Remeshing > Quadratic Edge colapse.

From the error message it sounds like the mesh may have been scaled differently in the export from meshlab.

Any help would be much appreciated, If anyone has managed to get this example or similar working in the current version I would be interested in obtaining a copy.

AttachmentSize
Plain text icon log.liggghts.txt2.87 KB
Plain text icon in.mixer_.txt2.76 KB

nlooije | Mon, 03/13/2017 - 21:15

Did you ever get this fixed?

I am running into the same problems with the provided mesh. However, my error is different:
WARNING: Fix mesh: Mesh contains highly skewed element, moving mesh (if used) will not parallelize well

CarlosRJ | Wed, 11/06/2019 - 02:38

I´m new user of LIGGGHTS, I´m working on a simulation that consist in a drum with a little hole at the bottom, and inside the drum a impeller. My goal is see the mixture of material, and the material at the outlet. Nevertheless, the trouble that I have right now is when I import the mesh for the drum and for the impeller I can´t have the impeller inside the drum. I review the documentation, but i don´t have a clear answer.
I attach part of the code i made. I hope someone could help to solve the trouble.
Regards,
CR

fix cad1 all mesh/surface file meshes/PropelTMesh.stl type 1 move 0. 0. 1.5 scale 0.001 &
rotate axis 1. 0. 0. angle 90
fix cad2 all mesh/surface file meshes/Drum_Op.stl type 1 move 0. 0. -0.4 scale 0.001 &
rotate axis 1. 0. 0. angle 90.