Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Want ripples on your icicles?

10.10.2013
University of Toronto scientists suggest adding salt

Though it's barely the beginning of autumn, scientists at the University of Toronto are one step closer to explaining why winter's icicles form with Michelin Man-like ripples on their elongated shapes.


This is a natural ripply icicle, collected to measure water composition.

Credit: Stephen Morris

Experimental physicist Stephen Morris and PhD candidate Antony Szu-Han Chen were spurred to investigate by the ripples that appear around the circumference of icicles that occur naturally. It has been theorized that the ripples are the result of surface tension effects in the thin water film that flows over the ice as it forms. Their investigation revealed that the actual culprit is salt.

"Nobody has systematically investigated what causes the ripples so we began growing them in the lab," said Chen, lead author of a paper published online this week in New Journal of Physics. Accounting for key factors that influence the shape of an icicle as it forms in nature – ambient temperature, flow rate of water and the motion of the air surrounding it – the researchers experimented with the composition of the source water.

"We had already tried Toronto tap water and found that it formed ripply laboratory icicles, when distilled water didn't," said Morris. "We also confirmed that melted rippled icicles taken from Toronto garages were very slightly salty, so that's what led us to pursue the composition factor."

Using pure distilled water, distilled water with small quantities of sodium chloride added, and Toronto tap water – which contains sodium chloride as well as many other impurities – they produced 67 samples grown under a broad range of conditions. The evolution of the icicle shapes over time was acquired from digital images using detection of their edges, which were then analyzed with computer image processing.

Ripple growth was not observed on distilled water icicles, whereas saltier icicles showed clear ripples that appear in a patchy way and sometimes grew as large as a few millimetres. The ripples were seen to move slowly upward during the icicle growth, though the researchers note that both the speed and direction of the ripple motion could vary depending on the concentration of dissolved salt.

Morris and Chen found that ripples only became apparent at the remarkably low salinity of the water with 20 mg of salt per litre. This level, in fact, is a considerably lower level of impurity than found in common tap water.

"We even added a non-ionic ingredient to the distilled water to reduce the surface tension of the thin film of water flowing over the icicle, and it didn't produce ripples," said Chen. "Instead, ripples emerge only on icicles grown from water with dissolved ionic impurities."

"Our motivation is pure curiosity about natural patterns, but the study of ice growth has serious applications, including ice accumulation on airplanes, ships and power lines," said Morris. "This result is totally unexpected, not just by us before we did this, but by theorists and experimentalists in our field who study ice dynamics and pattern formation."

"No theory accounts for the effect of salt, so the shape of icicles and the reason for their ripples are still mysteries. Except we now know that a little salt is required in the recipe."

The findings are reported in the paper "On the origin and evolution of icicle ripples". The research is supported by funding from the Natural Sciences and Engineering Research Council of Canada.

Note to media: Contact Sean Bettam at s.bettam@utoronto.ca for images and videos of the research described here.

MEDIA CONTACTS:

Stephen Morris
Department of Physics
University of Toronto
smorris@physics.utoronto.ca
416-978-6810
Antony Szu-Han Chen
Department of Physics
University of Toronto
aschen@physics.utoronto.ca
416-978-0137
Sean Bettam
Communications, Faculty of Arts & Science
University of Toronto
s.bettam@utoronto.ca
416-946-7950

Sean Bettam | EurekAlert!
Further information:
http://www.utoronto.ca

More articles from Physics and Astronomy:

nachricht Gamma rays will reach beyond the limits of light
23.10.2017 | Chalmers University of Technology

nachricht Creation of coherent states in molecules by incoherent electrons
23.10.2017 | Tata Institute of Fundamental Research

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: Salmonella as a tumour medication

HZI researchers developed a bacterial strain that can be used in cancer therapy

Salmonellae are dangerous pathogens that enter the body via contaminated food and can cause severe infections. But these bacteria are also known to target...

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

3rd Symposium on Driving Simulation

23.10.2017 | Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

 
Latest News

Microfluidics probe 'cholesterol' of the oil industry

23.10.2017 | Life Sciences

Gamma rays will reach beyond the limits of light

23.10.2017 | Physics and Astronomy

The end of pneumonia? New vaccine offers hope

23.10.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>