Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers move closer to understanding chaotic motion of a solid body in a fluid

24.02.2010
In a paper appearing in the Feb. 24 issue of the Proceedings of the Royal Society of London A, Virginia Tech Engineering Science and Mechanics Professor Hassan Aref, and his colleague Johan Roenby at the Technical University of Denmark shed new light on the chaotic motion of a solid body moving through a fluid.

They claim to have discovered two basic mechanisms that lead to chaotic motion of the body as it interacts with its vortex wake. The work may lead to better understanding and control of real body-vortex interactions.

Although it goes back to the work of Henri Poincaré at the end of the 19th century, chaos emerged in earnest as a new concept in science in the 1960s. Scientists then realized that even very simple systems, governed by perfectly deterministic laws, could have very complicated and seemingly random behavior. Anyone who has played with dice literally has had hands-on experience with the high sensitivity to initial conditions exhibited by a chaotic system. This makes long-term prediction of the system's evolution virtually impossible, Aref and Roenby explained.

It has long been known that the motion of a solid object through a fluid may be chaotic. Mechanisms that lead to chaotic motion in such systems are important, sometimes because one wants to avoid them, at other times because one wants to exploit them. For instance, when designing aircraft, one strives to prevent chaotic motion, whereas it might be a good strategy for a prey trying to escape a predator to enter a regime of erratic, unpredictable motion.

Fluid-body interactions are not very well understood. It is, however, reasonably well established that the delicate interplay between the body and the vortices shed from it, and present in the fluid, plays a key role. For example, it may be shown that if the motion is strictly two-dimensional and there are no vortices, chaos cannot occur. Chaos can occur for three-dimensional motion of a solid body through a fluid even in the absence of vortices.

To understand how vortices may create chaos in the body motion, Aref and Roenby studied a simplified body-vortex interaction model. The simplicity of the model allowed the scientists to take well-known, non-chaotic solutions as the starting point and then slowly increase the influence of parameters that would cause chaos to occur. It was by triggering the chaos in this controlled manner that the authors discovered two sources of chaos in the model.

The work "shows how a chaotic region grows from a specific type of equilibrium," the authors claimed. Aref and Roenby knew from classical hydrodynamics that a body in an "unbounded, ideal liquid has a limiting motion between the rocking and tumbling regime. Adding a vortex to this effectively acts as a random torque on the body." This is one mechanism for chaos. The other chaotic regime arises when the body is made slightly non-circular. For certain parameter regimes this renders the vortex motion, and thereby its force on the body, chaotic. "The kind of parametric scans we have performed may give important clues as to which geometries and parameter regimes to avoid, if one wants to prevent chaotic motion", the authors said.

As Aref, Roenby and others unravel the forces that come into play when vortices are produced through interaction between a solid body and the fluid surrounding it, they are furthering the understanding of aerodynamic and hydrodynamic forces, the drag and lift that are paramount in virtually all motion of bodies through air or water.

YouTube videos on the work can be found at http://www.youtube.com/user/JohanRoenbyPedersen

Aref is Virginia Tech's Reynolds Metals Professor of Engineering Science and Mechanics. He also holds a Niels Bohr Visiting Professorship at the Technical University of Denmark. Roenby is a Ph.D. student in the mathematics department and the Center for Fluid Dynamics at the Danish University. He is currently a visiting scholar at Imperial College, London.

Virginia Tech's College of Engineering is internationally recognized for its excellence in 14 engineering disciplines and computer science. As the nation's third largest producer of engineers with baccalaureate degrees, undergraduates benefit from an innovative curriculum that provides a hands-on, minds-on approach to engineering education. It complements classroom instruction with two unique design-and-build facilities and a strong Cooperative Education Program. With more than 50 research centers and numerous laboratories, the college offers its 2,000 graduate students opportunities in advanced fields of study, including biomedical engineering, state-of-the-art microelectronics, and nanotechnology.

Lynn Nystrom | EurekAlert!
Further information:
http://www.vt.edu
http://www.eng.vt.edu/main/index.php

More articles from Physics and Astronomy:

nachricht Matter falling into a black hole at 30 percent of the speed of light
24.09.2018 | Royal Astronomical Society

nachricht Scientists solve the golden puzzle of calaverite
24.09.2018 | Moscow Institute of Physics and Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists present new observations to understand the phase transition in quantum chromodynamics

The building blocks of matter in our universe were formed in the first 10 microseconds of its existence, according to the currently accepted scientific picture. After the Big Bang about 13.7 billion years ago, matter consisted mainly of quarks and gluons, two types of elementary particles whose interactions are governed by quantum chromodynamics (QCD), the theory of strong interaction. In the early universe, these particles moved (nearly) freely in a quark-gluon plasma.

This is a joint press release of University Muenster and Heidelberg as well as the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt.

Then, in a phase transition, they combined and formed hadrons, among them the building blocks of atomic nuclei, protons and neutrons. In the current issue of...

Im Focus: Patented nanostructure for solar cells: Rough optics, smooth surface

Thin-film solar cells made of crystalline silicon are inexpensive and achieve efficiencies of a good 14 percent. However, they could do even better if their shiny surfaces reflected less light. A team led by Prof. Christiane Becker from the Helmholtz-Zentrum Berlin (HZB) has now patented a sophisticated new solution to this problem.

"It is not enough simply to bring more light into the cell," says Christiane Becker. Such surface structures can even ultimately reduce the efficiency by...

Im Focus: New soft coral species discovered in Panama

A study in the journal Bulletin of Marine Science describes a new, blood-red species of octocoral found in Panama. The species in the genus Thesea was discovered in the threatened low-light reef environment on Hannibal Bank, 60 kilometers off mainland Pacific Panama, by researchers at the Smithsonian Tropical Research Institute in Panama (STRI) and the Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) at the University of Costa Rica.

Scientists established the new species, Thesea dalioi, by comparing its physical traits, such as branch thickness and the bright red colony color, with the...

Im Focus: New devices based on rust could reduce excess heat in computers

Physicists explore long-distance information transmission in antiferromagnetic iron oxide

Scientists have succeeded in observing the first long-distance transfer of information in a magnetic group of materials known as antiferromagnets.

Im Focus: Finding Nemo's genes

An international team of researchers has mapped Nemo's genome

An international team of researchers has mapped Nemo's genome, providing the research community with an invaluable resource to decode the response of fish to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

"Boston calling": TU Berlin and the Weizenbaum Institute organize a conference in USA

21.09.2018 | Event News

One of the world’s most prominent strategic forums for global health held in Berlin in October 2018

03.09.2018 | Event News

4th Intelligent Materials - European Symposium on Intelligent Materials

27.08.2018 | Event News

 
Latest News

Matter falling into a black hole at 30 percent of the speed of light

24.09.2018 | Physics and Astronomy

NASA balloon mission captures electric blue clouds

24.09.2018 | Earth Sciences

New way to target advanced breast cancers

24.09.2018 | Health and Medicine

VideoLinks
Science & Research
Overview of more VideoLinks >>>