A separated vortex ring underlies the flight of the dandelion ($) (Nature)

Dandelions, perennial herbs from temperate zones, have the capacity to spread their seeds through wind for distances as far as 1 km. Ignazio Maria Viola and Naomi Nakayama with their team endeavored to understand this passive flight mechanism. They analyzed the flight mechanism of the dandelion by characterizing the fluid dynamics of the pappus (thread-like modified calyx) to identify the key features responsible for stable flight. During flight, a stable air bubble is formed that is not attached to the body, called the Separated Vortex Ring (SVR). The authors found that the structure of the pappus stabilizes the SVR. They hypothesized that the circular disk-like geometry and the porosity of the pappus are key features in SVR formation. By deciphering the flight mechanism of the dandelion, they presented a novel type of fluid behavior around fluid-immersed bodies. (Summary by Arif Ashraf) Nature: 10.1038/s41586-018-0604-2   Nature Video: The secret physics of dandelion seeds