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Re: [lammps-users] Polydispsersity and random packing
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Re: [lammps-users] Polydispsersity and random packing

From: Axel Kohlmeyer <akohlmey@...24...>
Date: Mon, 12 Jun 2017 13:39:43 -0400

On Mon, Jun 12, 2017 at 12:24 PM, Roberts, Andrew <A.P.Roberts@...5884...> wrote:


I am new to LAMMPS, but I wondered if someone could tell me how to specify this for a 2D Couette flow:

  • 10% polydispersity on sphere diameter so that all the diameters (flow and walls) are randomly distributed between 0.9 and 1.1?

​this is easily done with an atom style variable and the set diameter command. after changing diameters, you will need to run some kind of (restricted) relaxation​ to remove overlaps.

  • Random packing of spheres in the flow region, but keep the walls packed in a straight line?

​just use two separate create_atoms calls on the different regions and request positions on lattice points in the first (the default) and random positions in the second. for random positions running some unoverlap relaxation is essentially. possibly you may need to use a different pair style, e.g. soft, and fix adapt to handle large overlaps smoothly. see the micelle example for how to do the latter.



The script I am working on is attached.

Kind regards,


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Dr. Axel Kohlmeyer  akohlmey@...12...24...
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.