# Rectangular bar discretised with bonded spherical elements with periodic B.C.'s

Hi!

I'm trying to discretise a 2D rectangular bar with spherical elements (just a single layer of spheres in the x-y plane) of approx. length (L-R) = 50 cm and width (B-T) = 5 cm, max_radius ~ 6e-04 m , min_radius ~ 2.5e-04 m. Material parameters can be arbitrary.

I want to impose periodic boundary conditions (particles on Left edge are repeated on Right side and have equal x-displacements e.g. particle A on LHS with x = 0 and y = 3 will be copied and placed at R.H.S. with lets say x = 50, y = 3 and in a sense are master-slave pairs with equal x displacements. Similarly for the top and bottom edges but with equal y-displacements.)

The end goal is to achieve avg. coordination no. > 5.5.

I have tried my luck with examples of periodic B.C.'s given in GitHub repository of YADE, but failed to achieve anything useful.

I will be grateful for any help.

Best,
Nik

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2019-02-20
2019-03-08
 Jan Stránský (honzik) said on 2019-02-20: #1

Hello Nik,

welcome :-)

> I have tried my luck with examples of periodic B.C.'s given in GitHub repository of YADE, but failed to achieve anything useful.

Please provide a MWE (minimum working example) [1] (unfortunately the wiki page is down currently) such that we know what you have tried already, we can tried your solution and basically see what exactly you are using.
Also please always try to be specific enough in the description of the problem, in this case:
- which examples have you tried (please ideally provide full patrhs to the examples or links to source code on github/gitlab)?
- what does "useful" mean? What did you get from the simulation and what you expected?

> I want to impose periodic boundary conditions (particles ... are repeated ... will be copied and placed ...)

Just a note, I personally call the yade implementation "periodic contact detection" rather then "periodic boundary conditions". The particles are not copied / repeated, but the collider (contact detection) knows about the *periodic images* of the particles.
Furthermore, the particles can have arbitrary position (outside the periodic cell), which needs to be taken into account for postprocessing.

cheers
Jan

 Launchpad Janitor (janitor) said on 2019-03-08: #2

This question was expired because it remained in the 'Needs information' state without activity for the last 15 days.