What is the correct syntax for servo control wall in LIGGGHTS 3.X?

Hi, All

I am trying to use the servo controlled wall (shear cell example in http://www.cfdem.com/forums/liggghts-tutorial) in LIGGGHTS 3.2.0 (the latest), there is always an error for the below lines (line 66-69), the file is attached:

fix cad3 all mesh/surface/stress/servo file top_plate.stl type 1 scale 0.001 &
stress on com 0 0 0.06 dim z ctrlPV force target_val -10.0 vel_max 1.0
fix geometry2 all wall/gran model hertz tangential history mesh n_meshes 1 meshes cad3

When I run this the liggghts 3.2.0 gives me the following error:

ERROR: Fix wall/gran (id geometry2): could not find fix mesh id you provided (../fix_wall_gran.cpp:249)

Could you please tell what is the correct syntax?

Thanks a lot for your help!

Roy

Attachment	Size
liggghts script	3.25 KB
scripts including stl files	59.52 KB

Forums:

LIGGGHTS® - User Forum

aaigner | Fri, 06/12/2015 - 12:54

Small mistake...

Hi Roy,

I can not check your case, since the stl-files are missing. But I found one obvious mistake. You defined two wall/gran. Check the documentation of the fix wall/gran. There is mentioned that ...
Restrictions:
There can be only one fix wall/gran command with style mesh. Note that this is not really a restriction because you can include multiple fixes of type fix mesh/surface in the fix wall/gran command.

Bests
Andreas

dbxmcf | Fri, 06/12/2015 - 15:54

Hi, Adnres:

Thanks for your response, I have also attached the entire package including the stl files, the same version of the script using liggghts ver 2.3.8 can work well, I am just trying to rewrite the script to the latest 3.2.0 version.

Thanks a lot for your help!

Roy

aaigner | Mon, 06/15/2015 - 15:51

Nasty small errors...

Hi Roy!

Let's go through the mistakes one by one:

The &-sign at the end of line 65 extends the comment to line 66, thus the meshcad3 is never defined. LIGGGHTS complains that it does not know cad3.
Fixing this, the new error message is then ERROR: Fix mesh/surface/stress/servo (id cad3): unknown keyword or wrong keyword order: dim (../fix_mesh_surface_stress_servo.cpp:218)
. That's the new syntax of LIGGGHTS 3.x.x. Replace dim z with axis 0. 0. 1.
Once more.. you may define only one wall/gran. So replace your geometry2 with
unfix geometry fix geometry all wall/gran model hertz tangential history mesh n_meshes 3 meshes cad1 cad2 cad3

Bests
Andreas

dbxmcf | Tue, 06/16/2015 - 17:31

Hi, Andreas:

Thank you for your valuable input, the 3.x scripts is now working, just one more question are the two operations:

unfix geometry and then
fix geometry necessary?

I tried remove the previous fix with cad1 and cad2 and only keep the last fix

fix geometry2 .... cad1 cad2 cad3

The script stopped with runtime error?

Thanks,

Roy

aaigner | Thu, 06/18/2015 - 15:24

Well.. what was the error

Well.. what was the error message?

As far as I understood your script, the original intention was that you insert the particles in the region bounded by cad1 and cad2. After this step you enable the particle-wall interaction with cad3 and start compressing the particles. If you want to stick to this procedure you have to unfix the original wall and make a new fix. (or just define the new fix with the same id... this should work too)

If you just remove the first fix wall/gran, there are no walls for your first run commands. (There are two between those insert/stream commands.)

Bests,
Andreas

srguya | Fri, 10/14/2016 - 13:55

Shear Cell Simulation

I am doing the same simulation as in this string, however I am getting the following error

ERROR: Mesh (id cad4): Mesh elements have been lost / left the domain. Please use 'boundary m m m' or scale/translate/rotate the mesh or change its dynamics (../multi_node_mesh_parallel_I.h:568)

Can you assist please

Regards
Solomon

j-kerbl | Mon, 10/17/2016 - 10:02

Hi Solomon,

what is the cad4 mesh? It is not in the input script.
It is outside of the fixed (f f f) simulation box: region reg block -0.325 0.325 -0.325 0.325 -0.001 0.081 units box

Please check your STL size.
You can additionally run a very short run with an even shorter dump interval and auto-expanding boundaries (m m m). Then you can double-check the sizes with the dump output of the stls.

Cheers,
Josef