Snow Globe Fluid Dynamics (2D Cross-Section)

This is a simplified vertical cross-section through a snow globe's viscous fluid — a genuinely different, reduced model from the full 3D version rather than a flattened reprojection of it. Shaking (via button or a click on the globe) injects a real Lamb-Oseen viscous vortex directly into the visible plane, and its core radius grows exactly as viscous diffusion predicts, fading the swirl over time. Every glitter particle is simultaneously advected sideways by that decaying in-plane flow and pulled down by its own Stokes-drag terminal velocity, v_t = 2r²(ρ_p−ρ_f)g/(9η), so you can watch the swirl visibly deflect the straight fall of denser or larger particles. Adjust viscosity, particle size, particle density and fluid density to see settling time and swirl pattern respond in real time, drag to pan and scroll to zoom into the action.