Contact model for wall/gran

Submitted by jpola on Thu, 08/18/2016 - 16:38

Hi,

currently I'm investigating if it is possible to create custom contact model for wall. I'm interested in having simple lubrication cohesion model when particle is in close proximity to the wall.

I've created new lubrication cohesion model which seems to be working for pair_gran style. Now I wish to have the similar model adopted for atom wall interactions.

The fix_wall_gran_base.h have field cmodel of type ContactModel. As I see from the code I should be able to define surfaceModel, normalModel, cohesionModel etc. Therefore I tried to execute configuration where for one of the primitive walls I defined following style

fix xwalls1 all wall/gran model hertz tangential cohesion lubrication mu 1.e-3 cutoff 1e-8 history primitive type 1 xplane -0.125

After starting the liggghts I have following error message saying that the configuration I gave for wall/gran is wrong

ERROR: Fix wall/gran (id xwalls1): unknown contact model or model not in whitelist. Possible root causes:
(1) it's a typo. Check the documentation of the contact model you are using.
(2) the contact model is not available in your installation. Check if a documentation for this.
contact model is available at all in your version.
(3) the model is part of a package which was not installed. Check the documentation for details.
(4) the model is available, but was not in the whitelist during compilation. Check if a file
src/style_contact_model.whitelist exists. If yes, modify it and re-compile.
(../fix_wall_gran.cpp:166)

I suspect that this is due fact that I have to put some additional code for autogenerating the possible wall/gran styles configurations.
Could you please help me where I can find them?

Regards,
Jakub.

ckloss's picture

ckloss | Mon, 10/03/2016 - 11:01

Hi Jakub,

you have an error in your syntax, you have to sepcify a tangential model!

Christoph

nasser225 | Thu, 10/27/2016 - 17:49

Hi Jakub / Christoph,

How do I correct this and get liggghts to process my script with custom model?

@Christoph: can you please elaborate on the 'tangential' model please? Include any file references that need to be edited.

Many thanks!

nasser225 | Fri, 10/28/2016 - 12:54

Hi Josef,

Many thanks, understood but I actually have a new model IN PLACE of the standard ones found in Liggghts (hertz, hertz_stiffness etc.) and I am not using any extra conditions so my script reads:

fix tank_wall all wall/gran model my_model mesh n_meshes 1 meshes cad1

and

pair_style gran model my_model

Is this not right? Am I missing something?

Thanks,

nasser225 | Fri, 10/28/2016 - 13:10

Also, is pair_style only relating to the particle interaction? And the wall/gran fix relates to the particle-surface interaction?