July 2, 2019
Calculations present that the variety of white filaments springing from the highest of a dandelion seed is optimized for regular flight, permitting the seeds to cruise lengthy distances by way of the air.
A fluff-topped dandelion seed can float by way of the air for greater than a kilometer earlier than it drifts to the bottom. In experiments final 12 months, researchers revealed that the white filaments within the fluff—identified collectively as a pappus—create a ring-shaped wake behind the seed that’s related to low strain and acts to maintain it aloft. Now Pier Giuseppe Ledda from the Swiss Federal Institute of Expertise in Lausanne (EPFL) and colleagues have theoretically modeled the airflow across the pappus, reproducing the experimentally measured wake and displaying that it offers the seed with regular flight capabilities. Ledda says that the outcomes present simplified physics mannequin can clarify complicated methods within the pure phrase. He additionally notes a sensible facet to the end result—it may very well be used to assist within the design of lightweight parachute-like units for objects which have the same dimension and mass to dandelion seeds.
The staff’s mannequin approximates the pappus as a group of rods which might be organized just like the spokes of a bicycle wheel. Utilizing commonplace equations from fluid dynamics, the staff calculated the circulation sample that’s created by the construction because it strikes by way of the air. As within the experiments, they discovered ring-shaped vortex of circulating air varieties immediately behind the pappus, which they confirmed offers a wake that’s secure sufficient to hold the seed a protracted distance. Altering the variety of spokes within the pappus, they discovered that regular cruising happens when the pappus incorporates about 100 filaments—the identical quantity present in actual seeds. Ledda says that the end result signifies that the morphology of the pappus has advanced to make sure secure flight.
This analysis is printed in Bodily Assessment Fluids.
Katherine Wright is a Senior Editor for Physics.