Gas Particle Dynamics in a Confined Box Using DSMC

Motivation

Fundamental physics of fluid motion arises from two microscopic processes: free transport of particles and their collisions.

Collisionless limit: A confined box isolates particle transport, enabling boundary reflections, and sampling without intermolecular complexity.
With collisions: The same framework extends naturally to study relaxation and transport coefficients.

Collisionless Gas Particle Motion in a Box

Contributor: Jeongjoon Lee (Sep 2025)

We consider the motion of gas particles confined within a simple box, modeled using the Direct Simulation Monte Carlo (DSMC) method. In the absence of intermolecular collisions, particle dynamics are dominated by free-flight trajectories interrupted only by boundary reflections. This setup serves as a 0D/1D testbed for DSMC implementations, allowing researchers to verify correctness of particle tracking, boundary handling, and statistical sampling.

\frac{\partial f}{\partial t} + c_i \frac{\partial f}{\partial x_i} = 0 \qquad \text{(collisionless limit)}