Home▸Physics & Mechanics▸DSMC Rarefied Gas Flow Simulator

💨 DSMC and Rarefied Gas Flow

Interactive 3D particle simulation of a low-density gas where adjusting Knudsen number shows individual molecule collisions, via Direct Simulation Monte Carlo, replacing continuum fluid behaviour.

Physics & Mechanics3DModerate60 FPS

Watch a molecular gas stream past a plate and see how the Knudsen number determines whether it behaves like a smooth continuum fluid or a spray of independently colliding particles, using a Direct Simulation Monte Carlo collision model.

🔬 What It Demonstrates

Particles are grid-binned into cells each frame and stochastically paired for probabilistic collisions — the core DSMC move — with pairing probability falling as Knudsen number rises, reproducing the transition from continuum to free-molecular flow.

🎮 How to Use

Drag the Knudsen number slider from dense (continuum) to rarefied (free-molecular) and watch the flow regime badge and deflection pattern change. Adjust particle count and stream speed, and toggle collision flashes and velocity streaks.

💡 Did You Know?

NASA uses DSMC, developed by Graeme Bird, to predict aerodynamic heating and drag on spacecraft in the thin upper atmosphere during the rarefied phase of re-entry, before ordinary CFD becomes valid.

⚙ Under the hood

Interactive 3D particle chamber where lowering gas density shows how direct simulation Monte Carlo models individual molecule collisions once continuum flow breaks down.

dsmcrarefied-gas-dynamicskinetic-theorymolecular-collisionsknudsen-numberphysics

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install