Superb autorotator: rapid decelerations in impulsively launched samaras
| Autor: | Robert Dudley, Noah Suk-Won Kim, Victor Manuel Ortega-Jimenez |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Seed dispersal
Biomedical Engineering Biophysics Acer Bioengineering Wind engineering.material Models Biological Biochemistry Biomaterials symbols.namesake Range (aeronautics) Seed Dispersal Life Sciences–Engineering interface Maple Autorotation (fixed-wing aircraft) Reynolds number Mechanics Lift (force) Drag Seeds symbols engineering Descent (aeronautics) Geology Biotechnology |
| Zdroj: | Journal of The Royal Society Interface. 16:20180456 |
| ISSN: | 1742-5662 1742-5689 |
| DOI: | 10.1098/rsif.2018.0456 |
| Popis: | Autorotation of botanical samaras, with a consequent reduction in their rate of descent, increases dispersal range in the presence of horizontal winds. Samaras in initial free fall from rest pass through a brief transitional phase prior to reaching their minimum rate of descent and stable autorotation. By contrast, intense wind gusts and elastic recoil of tree branches can produce impulsive samara detachment and accelerate them rapidly through the air. Here, we investigate the autorotation of maple samaras when launched with a high initial impulse. Norway maple seeds catapulted either vertically or horizontally at approximately 9 m s−1exhibited remarkably high and rapid decelerations (10–15g) and reached a near-zero translational speed in less than 150 ms. The initial rotational frequency of catapulted seeds was up to four times greater than that ultimately reached during steady-state autorotation. These helicopter seeds thus transiently produce very high lift forces (at Reynolds numbers near approximately 104) that act to enhance aerial transport. These findings are relevant to the modelling of long-distance seed dispersal in unsteady flows, as well as to the design of deceleration mechanisms based on lift generation, rather than drag-based devices such as parachutes. |
| Databáze: | OpenAIRE |
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