DSMC (Direct Simulation Monte Carlo)

Update (12/15/2025): See the branch convert-to-metal for a peek at the ongoing effort to port the project to run on Apple Silicon GPUs with Metal. Ray-tracing using Metal acceleration structures is also being leveraged there to add support for arbitrary geometries embedded in the computational domain.

Example

Heat diffusion through Argon gas at STP when the bottom boundary is hot:

• There are 10^5 simulated particles, each representing ~270 million Argon atoms
• The side length of the cubic domain is 100 microns
• The computational grid is 2x2
• Reflection off of the domain boundaries is diffuse

Initial snapshot	.	.	.

Overview

This project aims to use Direct Simulation Monte Carlo (DSMC) methods for modeling (dilute) gas flow.

The goal is to later extend this project to support simulation of dense gases / fluids.

See this page for mathematical background and more information.

TODOs

• Switch this project over to Metal for Apple Silicon, with CMake-generated XCode project
• Use the new way of Metal ray-tracing to do intersection queries with an object embedded in the DSMC domain
  • https://developer.apple.com/documentation/metal/ray-tracing-with-acceleration-structures
• Revisit boundary conditions