Subscribe to our free daily newsletters
. 24/7 Space News .




Subscribe to our free daily newsletters



TECH SPACE
Daffodils help inspire design of stable structures
by Staff Writers
Washington DC (SPX) May 12, 2016


The unique geometry of the daffodil stem could be used to design more stable structures. Image courtesy 2016 Sally J. Bensusen/Visual Science Studio. For a larger version of this image please go here.

In 1940, the Tacoma Narrows Bridge collapsed in dramatic fashion, twisting in the wind before it snapped and plunged into the water below. As wind blew across the span, the flow induced oscillating sideways forces that helped bring down the bridge - just months after opening. This type of side-force oscillation can also damage antennae, towers and other structures.

Now, researchers from Seoul National University and Ajou University in South Korea have found that a structure with a twisted, helical shape and an elliptical cross section - inspired by the stem of a daffodil - can reduce drag and eliminate side-force fluctuations. The researchers describe their findings this week in Physics of Fluids, from AIP Publishing.

Side forces come into play whenever wind flows across an elongated object - like when you stick your arm out the side of a moving car. As the air flows around your arm, it forms vortices that come off the top and bottom of your arm in an alternating fashion. This vortex shedding, as it's called, imparts periodic forces on your arm.

"You will immediately feel that your arm will be forced to move up and down," explains Haecheon Choi of Seoul National University. This phenomenon, called von Karman vortex shedding, affects any elongated structure caught in wind or water currents such as lampposts, high rises and the long vertical pipes used for drilling oil at sea.

In the case of the Tacoma Narrows Bridge, the frequency of these periodic forces happened to hit its resonant frequency. "This vortex shedding triggered the twisting mode of the bridge," Choi said, "and finally the bridge collapsed."

To find a way to reduce these forces, the researchers looked to nature for inspiration. Specifically, they studied the shape of a daffodil stem, whose twisting, lemon-shaped cross-section enables it to turn away from wind and protect its petals.

The researchers used computer simulations to explore the fluid dynamics around the daffodil stem's shape: a helically twisted, elliptical cylinder. They tested different variations - some with more elliptical cross-sections or with more twists, for example - in smooth, laminar airflow or a more turbulent wind.

In both cases, the daffodil shape made a big difference.

"Some helically twisted cylinders annihilated the vortex shedding, resulting in drag reduction and zero side-force fluctuations," Choi said. Compared to a round cylinder, the daffodil shape reduced drag by 18 and 23 percent, respectively, for laminar and turbulent flows.

The unique geometry of the daffodil stem could be used to design more stable structures. Although such a shape probably doesn't make sense for a bridge, it could work for things like antennae, lampposts, chimneys, underwater oil-drilling pipes, sky-scrapers and even golf clubs. In fact, Choi said, the researchers already have a patent for a helical golf club.

Research paper: "Flow around a helically twisted elliptic cylinder,"


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

.


Related Links
American Institute of Physics
Space Technology News - Applications and Research






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
TECH SPACE
Machine learning accelerates the discovery of new materials
Los Alamos NM (SPX) May 10, 2016
Researchers recently demonstrated how an informatics-based adaptive design strategy, tightly coupled to experiments, can accelerate the discovery of new materials with targeted properties, according to a recent paper published in Nature Communications. "What we've done is show that, starting with a relatively small data set of well-controlled experiments, it is possible to iteratively guid ... read more


TECH SPACE
NASA research gives new insights into how the Moon got inked

First rocket made ready for launch at Vostochny spaceport

Supernova iron found on the moon

Russia to shift all Lunar launches to Vostochny Cosmodrome

TECH SPACE
The rise and fall of Martian lakes

Opportunity microscopic imaging camera back to normal operations

Second cycle of Martian seasons completing for Curiosity Rover

Flying observatory detects atomic oxygen in Martian atmosphere

TECH SPACE
Out of this world: 'Moon and Mars veggies' grow in Dutch greenhouse

NASA Invests in Next Stage of Visionary Technology Development

NASA makes dozens of patents available in public domain

Pentagon's research agency showcases future tech

TECH SPACE
Long March-7 rocket delivered to launch site

China's space technology extraordinary, impressive says Euro Space Center director

China can meet Chile's satellite needs: ambassador

China launches Kunpeng-1B sounding rocket

TECH SPACE
ISS completes 100,000th orbit of Earth: mission control

Canadian astronaut to join ISS in 2018

NASA, Space Station partners announce future mission crew members

New landing date for ESA astronaut Tim Peake

TECH SPACE
Pre-launch processing is underway with Indonesia's BRIsat for the next Arianespace heavy-lift flight

New Antares Rocket Rolls Out at NASA Wallops

First work platforms powered tested in VAB for Space Launch System

SpaceX's Dragon cargo ship splashes down in Pacific

TECH SPACE
Star Has Four Mini-Neptunes Orbiting in Lock Step

Exoplanets' Orbits Point to Planetary Migration

Synchronized planets reveal clues to planet formation

Kepler space telescope finds another 1284 exo planets

TECH SPACE
Scientists take a major leap toward a 'perfect' quantum metamaterial

UW team first to measure microscale granular crystal dynamics

Self-healing, flexible electronic material restores functions after many breaks

Digital "clone" testing aims to maximize machine efficiency




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement