Boundary Conditions, Continuum Mechanics

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Discussion Overview

The discussion revolves around the formulation of boundary conditions for a continuum model of particles, specifically focusing on implementing periodic boundary conditions that allow for specular reflection of a fraction of incoming particles. The scope includes theoretical considerations and mathematical modeling within continuum mechanics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant questions how to express periodic boundary conditions mathematically for a continuum model of particles, particularly focusing on specular reflection.
  • Another participant suggests that a probabilistic equation could be appropriate for modeling the behavior of particles, raising the question of what happens to particles that are not reflected.
  • A different participant discusses the possibility of modeling a large number of particles as a continuous density and momentum function, and inquires about formulating a probabilistic equation as a boundary condition for a differential equation.
  • One participant asks if a lattice Boltzmann approach is being used, referencing relevant literature on boundary conditions in lattice Boltzmann methods and related studies.

Areas of Agreement / Disagreement

Participants express different viewpoints on the modeling approach and the formulation of boundary conditions, indicating that multiple competing views remain without a consensus on the best method to apply.

Contextual Notes

The discussion does not resolve the assumptions regarding the transition from discrete particles to a continuum model, nor does it clarify the specific mathematical steps needed to derive the boundary condition equations.

NeoDevin
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Mods: I wasn't sure if I should put this here or in DE's, if you think it would be better there, feel free to move it.

Everyone:
If I have a bunch of particles, which I'm modelling as a continuum, and I want to put periodic boundary conditions which reflect (completely specular reflection) some fraction of the incoming particles, how would I write this as a boundary condition equation?

Thanks in advance.
 
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Leaving aside the question of how a collection of discrete particles are modeled as a continuum, I would think that a probabilistic equation would do just fine. What happens to the particles that are not reflected?
 
If you have enough particles, you can model them as a continuous density function and velocity/momentum function.

How would you formulate a probabilistic equation in terms of a boundary condition for a differential equation.

The particles not reflected are transmitted.
 
Are you using some sort of lattice Boltzmann approach?

Shiyi Chen and Daniel Martínez, Renwei Mei
On boundary conditions in lattice Boltzmann methods
Phys. Fluids 8, 2527 (1996); DOI:10.1063/1.869035

Title: Absorbing boundary and free-surface conditions in the phononic lattice solid by interpolation
Authors: Huang, L.-J., Mora, P., & Fehler, M. C.
Journal: Geophysical Journal International, Volume 140, Issue 1, pp. 147-157.

Jeng-Rong Ho, , Chun-Pao Kuo and Wen-Shu Jiaung
Study of heat transfer in multilayered structure within the framework of dual-phase-lag heat conduction model using lattice Boltzmann method
International Journal of Heat and Mass Transfer
Volume 46, Issue 1, January 2003, Pages 55-69

There's plenty more, I'm sure. I'm, not an expert, those are what I was able to quickly find.
 

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