Each pappus (the fluffy parachute on a dandelion seed) is modeled with real quadratic aerodynamic drag: F = ยฝยทCdยทฯยทAยท|vrel|ยทvrel, using a ~5 mm effective disk radius, ~0.5 mg seed mass and an elevated drag coefficient (Cdโ1.5). That elevated Cd is real: at the pappus's tiny Reynolds number (~10-20), airflow separates and rolls up into a detached vortex ring hovering just above the porous canopy, roughly quadrupling the drag a solid disk that size would get โ which is what lets something this light sink at only ~0.26 m/s instead of tumbling down like a denser particle.
- Terminal fall speed โ set purely by mass, size and that drag coefficient; independent of wind. Shown above as the theoretical value from the same physics the sim integrates.
- Wind entrainment โ the same drag law acts on the horizontal slip between seed and air, so a seed's sideways speed relaxes toward the wind speed on the same fast timescale as its vertical terminal fall โ light, high-drag objects like this pappus become passive tracers of the airflow almost immediately.
- Wind speed โ raise it to sweep seeds sideways faster while they still sink at the same slow rate; the "measured sink rate" box tracks the live average vertical speed of drifting seeds so you can check it converges to the terminal value regardless of wind.
- Blow โ a gust that knocks loose a burst of seeds still attached to the receptacle; seeds also detach gradually on their own once wind is blowing, exactly as a real head sheds its seeds over time.