Doubts related to temperature of particles and normal overlap

Submitted by Manish_iNDIA on Sat, 02/06/2021 - 11:25

Q1. Does liggghts control maximum normal overlap between particles or is there no limit to maximum normal overlap?

Q2. How is temperature related to kinetic energy of each particle? What will happen if temperature is not maintained constant for simple granular flows?

Q3. How to create initial lattice of particles (specifically, how to increase the packing fraction of initial lattice of particles?)

I'll be grateful if I can get responses as soon as possible as I've to add these things to my master's thesis.

Thank you!

Forums:

mschramm | Sat, 02/06/2021 - 19:38

Hello,
1) what do you mean by control normal overlap?
This would be controlled by your timestep. A timestep too high and you can get large overlaps that lead to unstable simulations.

2) ke does not use temperature in its calculation

3) See the follwoing for inserting particles on a lattice (https://www.cfdem.com/media/DEM/docu/lattice.html)
You may also want to look at the packing example.

Manish_iNDIA | Fri, 02/12/2021 - 09:50

Thanks for replying.

I have written my own code in 'C' to simulate the collapse of granular column.

For the case without dissipation, i checked my results for energy conservation. Thereafter, i compared it with liggghts results but they don't match. The spread of the collapsing granular column at the end of two seconds is different from both the results. Hence, i thought maybe there's a cutoff to max normal overlap in liggghts.

I've taken the same initial lattice and material properties and size.

Any thoughts?

deepakpawar.2310 | Sat, 02/13/2021 - 06:43

Hi

If possible, can you show your results. Are you plotting the variation of kinetic energy?

(1) You tested the energy conversion, as you said. How you monitored work-energy balance during the simulation?
(see the attached on work-energy balance, might be helpful, https://www.cfdem.com/forums/output-total-energy)

(2) Collaposiong of granular assembly, it is what you expecting, If not then it seems to be unstable DEM simulation due to various reason.

Thanks

Happy learning !!