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

Subscribe to our free daily newsletters

Clever experiment documents multiscale fluid dynamics
by Staff Writers
Chicago IL (SPX) Aug 07, 2017

Volumetric image of a helical vortex leapfrogging through a vortex ring in water, with dye-blob tracks overlaid in warm colors. Credit William Irvine/University of Chicago

University of Chicago physicists working in the nascent field of experimental vortex dynamics have, with unexpected help from a Sharpie marker, achieved the first measurements of an elusive but fundamental property of fluid flow.

Until now, there had been no way in the laboratory to measure the total helicity, or the measure of when two vortex rings intertwine. In their experiments, the UChicago team created thin-core vortices - the kinds found in aircraft wakes and insect flight - by producing hydrofoils using a 3-D printer.

As luck would have it, the red Sharpie marker used to label the hydrofoils contained rhodamine dye, which fluoresced when illuminated by laser light. When the hydrofoils were placed in a water tank, the dye began to diffuse, and when the hydrofoil was accelerated, the dye got sucked into the core of the newly created vortex - a process recorded via high-speed laser scanning tomography.

The new findings, published Aug. 3 in Science, are the first to show that helicity maintains a constant value during the flow of viscous fluids. Vortex dynamics have important applications in everyday life; meteorologists, for example, view helicity as a factor that contributes to the formation of supercell tornadoes.

"The fact that we have some measurements for the first time that show helicity can be preserved, especially in the presence of stretching, can translate directly to those efforts," said William Irvine, an associate professor in physics, who published the findings along with four co-authors.

Twists and turns
In their latest research, the physicists studied three related forms of helicity: twisting, linking and writhing. The three forms are simply different ways to describe geometrically related forms that have been twisted or stretched. Each vortex tube can be visualized as a bundle of filaments, similar to those bound together in a twisted rope.

"If you take a piece of rope or or a telephone cord and you coil it up, then we would say that the center of this rope or telephone cord is writhing," Irvine said. "And if we then took this thing that we coiled up and we pulled it straight, you would see twisting along its length."

Simulating helicity in those flows has been difficult because of the widely separated yet interconnecting scales in which they operate. Previous work had been largely theoretical and involved hypothetical, simpler fluids totally lacking in viscosity. Calculations showed that helicity was conserved in these hypothetical fluids, but viscosity emerged as a significant factor in the flow of actual fluids.

"One of the core problems is that you need to sample or measure features of the flow that exist on very different length scales," said Martin Scheeler, the study's lead author, who recently completed his doctorate in physics at UChicago. The scales range from the diameter of a vortex (approximately 30 centimeters or one foot) to the diameter of its thin core (approximately one milllimeter or three hundredths of an inch).

"You need to measure the flow inside the core as well as the overall shape evolution of that vortex," Irvine said. "That's quite a separation." He characterized Scheeler's work in overcoming the experimental challenges - simultaneously tracking the fine details of the flow while still measuring the critical larger-scale dynamics - as "a tour de force."

'It's the wackier stuff that works'
Irvine's group had previously used bubbles to conduct pioneering research on the dynamics of vortices in their water-tank experiments. The helicity measurements, however, required something different, which was provided serendipitously through the Sharpie.

Dye has long been used in vortex experiments, but less precisely. In previous experiments, the dye was placed diffusely in the tank, and then the vortices would envelope them. But the Sharpie presented an opportunity to precisely position the dye at the center of the vortices, as Scheeler painstakingly painted dots onto the entire length of the hydrofoils.

"We hadn't really realized that that was a possibility until we saw dye bleeding off the hydrofoil," said Scheeler, who valued the creativity and freedom involved in designing experiments for a nascent field of physics.

"There really is no playbook, and that's really exciting," he said. "You get to try out all sorts of different things, and sometimes it's the wackier stuff that works."

Citation: "Complete measurement of helicity and its dynamics in vortex tubes," by Martin Scheeler, Wim M. van Rees, Hridesh Kedia, Dustin Kleckner, and William T.M. Irvine. Science.

Physicists design ultrafocused pulses
Innsbruck, Austria (SPX) Jul 31, 2017
Microwaves, heat radiation, light and X-radiation are examples for electromagnetic waves. Many applications require to focus the electromagnetic fields to small spatiotemporal dimensions. Engineers may use different methods to achieve this. In the journal Physical Review Letters, researchers in Oriol Romero-Isart's group at the Institute of Quantum Optics and Quantum Information (IQOQI) an ... read more

Related Links
University of Chicago
Understanding Time and Space

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

Comment using your Disqus, Facebook, Google or Twitter login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

NASA Offers Space Station as Catalyst for Discovery in Washington

Let's cut them off from access to Space

ESA astronaut Paolo Nespoli starts third mission on Space Station

NextSTEP Partners Develop Ground Prototypes to Expand our Knowledge of Deep Space Habitats

ISRO Develops Ship-Based Antenna System to Track Satellite Launches

India looks to more launches with new facility from 2018

Sea Launch to be modernized for Russia's Soyuz-5 carrier rocket

Navy completes testing fixes on electro-magnetic launch systems

For Moratorium on Sending Commands to Mars, Blame the Sun

Tributes to wetter times on Mars

Opportunity will spend three weeks at current location due to Solar Conjunction

Curiosity Mars Rover Begins Study of Ridge Destination

China develops sea launches to boost space commerce

Chinese satellite Zhongxing-9A enters preset orbit

Chinese Space Program: From Setback, to Manned Flights, to the Moon

Chinese Rocket Fizzles Out, Puts Other Launches on Hold

ASTROSCALE Raises a Total of $25 Million in Series C Led by Private Companies

LISA Pathfinder: bake, rattle and roll

Airbus DS to expand cooperation with Russia

UK space companies to develop international partnerships

Algorithms that can sketch, recreate 3-D shapes

Nanoparticles for 3-D printing in water open door to advanced biomedical materials

WSU physicists turn a crystal into an electrical circuit

Researchers set new record for tape storage

A New Search for Extrasolar Planets from the Arecibo Observatory

Gulf of Mexico tube worm is one of the longest-living animals in the world

Molecular Outflow Launched Beyond Disk Around Young Star

Breakthrough Starshot launches tiny spacecraft in quest for Alpha Centauri

New Horizons Video Soars over Pluto's Majestic Mountains and Icy Plains

Juno spots Jupiter's Great Red Spot

New evidence in support of the Planet Nine hypothesis

NASA's New Horizons Team Strikes Gold in Argentina

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