Subscribe free to our newsletters via your
. Space Industry and Business News .

Star-shaped waves spotted in shaken fluid
by Hamish Johnston
London, UK (SPX) Mar 13, 2013

These photographs show two wave-crest patterns created when silicon oil is vibrated. At certain vibration amplitudes, the pattern oscillated between the star-like (left) and pentagonal (right) shapes. (Courtesy: Jean Rajchenbach, Didier Clamond and Alphonse Leroux Phys. Rev. Lett. 110 094502).

A new wave phenomenon in liquids has been spotted by physicists in France. By shaking small cylindrical dishes of silicone oil, the team created standing waves that spontaneously form a range of patterns, including stars and polygons.

Calculations suggest that the shapes are caused by nonlinear interactions between "gravity waves" - the name given to any fluid wave in which gravity is the dominant restoring force. The researchers hope that their work could lead to a better understanding of other nonlinear gravity waves such as tsunamis and rogue ocean waves.

Gravity waves normally interact in a linear manner - much like light waves - but nonlinear interactions can also play an important role in how they are created and propagate. Indeed, some physicists think that nonlinear effects could be responsible for the giant "rogue" waves that are occasionally created in the Earth's oceans.

To study nonlinear effects, Jean Rajchenbach, Didier Clamond and Alphonse Leroux at the University of Nice looked at gravity waves in silicone oil. Water and oil are both Newtonian fluids, but the latter is easier to work with in the lab because its greater viscosity supports larger-amplitude waves.

Two types of wave
The experiments were carried out in shallow cylindrical dishes that were 9 cm in diameter and filled with 7 mm of oil. The dishes were placed on a vertically vibrating stage and the team could control two parameters: the frequency and amplitude of the vibration. With the frequency set at 8 Hz, the team noticed that, at small amplitudes, waves created at the edge of the container propagate inwards creating ripples that oscillate at the same frequency as the stage.

But as the amplitude was increased beyond about 1.55 mm, however, two counter-propagating waves appeared. These are a "centrifugal" wave that moves outwards from the centre of the dish and a "centripetal" wave that moves inwards from the edge. At relatively low amplitudes this resulted in a standing wave pattern of concentric rings.

Closer inspection revealed that where the crests of the centrifugal and centripetal waves cross, they do not simply superimpose as linear waves do. Instead, the waves experience a phase shift similar to that seen when two plane-wave solitons cross.

Stars and pentagons
As the vibrational amplitude was further increased to about 1.85 mm, five "corners" began to appear in the crest where the two waves cross. This creates a pentagon-shaped crest that breaks the circular symmetry of the dish.

Finally, when the amplitude was cranked up to 1.95 mm, the crest oscillated between a pentagon and a five-pointed star with a frequency of 8 Hz (see image). An amazing feature of this oscillating structure is that it does not depend on the shape or size of the container - and even appeared in rectangular-shaped containers.

To understand this bizarre behaviour, the researchers were inspired by theories that describe the formation of quasicrystals in solids and quasipatterns in capillary waves - tiny waves in fluids that are not affected by gravity.

They created a theory that, says Clamond, can predict the amplitudes at which the system transforms from one standing-wave configuration to another - but falls short of predicting which shapes the standing wave will assume.

New theory needed
Clamond believes that more work is needed to develop a new theoretical framework for understanding why the shapes form. Indeed, he likens the current situation to when physicists did not have a good theoretical understanding of solitons. But beyond explaining a curious laboratory phenomenon, understanding why the patterns emerge could lead to a better understanding of nonlinear waves in the ocean.

The research is described in Physical Review Letters.


Related Links
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 DiggDigg RedditReddit GoogleGoogle

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

Researchers Solve Riddle of What Has Been Holding Two Unlikely Materials Together
Raleigh NC (SPX) Mar 12, 2013
For years, researchers have developed thin films of bismuth telluride (Bi2Te3) - which converts heat into electricity or electricity to cooling - on top of gallium arsenide (GaAs) to create cooling devices for electronics. But while they knew it could be done, it was not clear how - because the atomic structures of those unlikely pair of materials do not appear to be compatible. Now resear ... read more

Aspirin may lower melanoma risk

NIST quantum refrigerator offers extreme cooling and convenience

Researchers Solve Riddle of What Has Been Holding Two Unlikely Materials Together

Star-shaped waves spotted in shaken fluid

Boeing Ships 5th WGS Satellite to Cape Canaveral for 2013 Launch

INTEROP-7000 uses ISSI to link IP-based voice comms with legacy radio

Space race under way to create quantum satellite

Boeing Receives USAF Contract for Integrated C4ISR Targeting Solution

Grasshopper Successfully Completes 80M Hover Slam

Musk: 'I'd like to die on Mars'

Ariane 5 vehicle for next ATV resupply mission in Kourou

Vega launcher integration continues for its April mission

China city searching for 'modern Marco Polo'

Milestone for European navigation system

China targeting navigation system's global coverage by 2020

Russian GLONASS space satellite group again at full strength

Boeing, KLM Demonstrate New Technologies to Optimize Flight

Singapore in 'final stages' of evaluating F-35

Embraer urges quick resolution of US contract challenge

EU safety body certifies Airbus A400M army transporter

Quantum computing moves forward

Creating indestructible self-healing circuits

Improving Electronics by Solving Nearly Century-old Problem

UCSB physicists make discovery in the quantum realm

Significant reduction in temperature and vegetation seasonality over northern latitudes

GOCE: the first seismometer in orbit

Japan's huge quake heard from space: study

Space station to watch for Earth disasters

Little faith in China leaders' pollution promises

Dead pigs contaminating Chinese river?

Toxic gas leak in South Korea, 11 hospitalised

Japan warns about smog drifting from China

The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal 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. 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