Printer Friendly

Spinning to a prismatic beat.

A cylinder mounted so that it stands upright on a turntable has no tendency to spin when air rushes by -- but a similarly mounted flat plate or three-sided prism not only spins but also generates lift in such an airstream. This aerodynamic effect, known as autorotation, plays an important role in determining the paths followed by freely falling, geometrically complicated objects, ranging from tree fruits to parts ejected from space-craft or airplanes.

Recent experiments by mechanical engineer B.W. Skews of the University of the Witwatersrand in Johannesburg, South Africa, reveal that only prisms with fewer than eight sides rotate in an airstream, and that prisms of a triangular cross section spin fastest. In each case, the spinning prisms generate more lift than they would if driven at the same rotation rate by a motor of some kind. Reporting in the Aug. 8 NATURE, Skews suggests that his findings could influence the design of wind-power devices, such as wind-driven rotors used to propel ships. The findings may also shed light on the behavior of wind-buffeted, many-stranded ropes and cables, which sometimes have cross sections resembling those of multifaceted prisms.
COPYRIGHT 1991 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:prisms and autorotation
Publication:Science News
Date:Aug 31, 1991
Previous Article:Data transfer via noisy neurons.
Next Article:Digital security signed, sealed, delivered.

Related Articles
The mystery of color & light ... an introduction to light refraction.
Fiberoptic headlight.
Grampaw pettibone.
Sargent Art, Inc.[R].
Shell microstructure, mineralogy and in vitro crystallization studies on the shell soluble matrix of abalone, Haliotis discus hannai Ino.
SUSANS with polarized neutrons.

Terms of use | Copyright © 2017 Farlex, Inc. | Feedback | For webmasters