output cohesion force only

Submitted by gelinhan on Thu, 03/22/2018 - 00:36

Hi all,

Is there any command or method to output the cohesion force only?

Kind regards,
Linhan

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richti83's picture

richti83 | Fri, 03/23/2018 - 07:55

As the force is added to the particle forces in cohesion_xxxxx model I think not without some coding**, but you can calculate the cohesion force in postprozessing using a compute pair/gran/local [1], a dump local [2],[3] and a calculator-filter in ParaView representing the corresponding formula.

Best,
Christian.

[1] https://www.cfdem.com/media/DEM/docu/compute_pair_gran_local.html
[2] https://www.cfdem.com/media/DEM/docu/dump.html
[3] https://www.cfdem.com/comment/14641#comment-14641

**one could a new property/atom and store the result of force calculation in it, have a look at fix_massflow_mesh.cpp, fix_counter_ how to do add a new fix on code level and how to access it. On scriptlevel you could than dump f_myCohesionForce directly to particle dumpfile.

I'm not an associate of DCS GmbH and not a core developer of LIGGGHTS®
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gelinhan | Fri, 03/23/2018 - 10:24

Hi Christian,

Thanks for the information. I will try to do it at code level.

Cheers,
Linhan

jagan1mohan | Mon, 11/30/2020 - 12:51

Hello Richti83, greetings. I have added vdw forces on top of normal_model_hooke. I switch this force via flag "vdw on" in input script in pair style. That is, I created a local variable Fn_vdw which is calculated only when "vdw on" and it is added to the already existing variable Fn inside this file. In dump, fx fy fz is sum total of all forces acting on each particle, how can we create or dump only vdwx vdwy vdwz inside code for only vdw contribution? I want to use property/atom modification but not sure where to add these lines. How are we telling LIGGGHTS to pick van der Waals force value from normal_hooke_model.h? Thank you, Jagan Mohan.