Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Physicists discover mechanism behind granular capillary effect

24.05.2017

Dipping a tube into a container filled with water will make the water rise in the tube. This phenomenon is called liquid capillarity. It is responsible for many natural and technical processes, for example the water absorption of trees, ink rising in a fountain pen, and sponges absorbing dishwater. But what happens if the tube is dipped into a container filled not with water but with sand? The answer is - nothing. However, if the tube is shaken up and down, the sand will also begin to rise. Scientists have now discovered the mechanism behind this effect, the so-called granular capillary effect.

Dr Eric J. R. Parteli from the University of Cologne's Department of Geosciences, Professor Fengxian Fan from the University of Shanghai for Science and Technology, and Professor Thorsten Pöschel from Friedrich-Alexander University Erlangen-Nürnberg have now published the results of their study 'Origin of Granular Capillarity Revealed by Particle-Based Simulations' in the Physical Review Letters.


When a narrow tube is dipped into granular material and vibrated vertically, the granular material rises inside the tube to reach a terminal vertical level.

Credit: Fengxian Fan, Eric Parteli, Thorsten Pöschel

Liquid capillarity results from the interplay of different molecular forces: the attraction between the liquid molecules keeps it together while the attraction between molecules and tube drives the liquid upward. This explanation precludes the occurrence of capillarity for sand because sand grains are so much bigger than their constituent molecules that inter-molecular forces can be safely neglected compared to gravity and grain inertia.

However, surprisingly, granular capillarity has been observed in laboratory experiments in which the granular material was subjected to a tiny vertical vibration of a few grain diameters in amplitude and a frequency of just a few Hertz. The origin of this granular capillary effect was a long-standing mystery the international team of scientists succeed in unveiling.

They investigated the problem using a particle-based numerical simulation method called Discrete Element Method. In this method, the trajectory of every single grain is calculated by numerically solving Newton's equations of translational and rotational motion due to the forces that act on each grain. By means of such a numerical experiment, it is thus possible to track the trajectory and velocity of all grains, including those grains that are deep within the granular bulk, which are difficult to assess in the laboratory.

The research team observed in their simulations that what makes the sand column ascend in the tube is a convective motion of the sand grains within the recipient that is inherent to granular materials under vertical vibrations. This convective flux causes lateral mass transport within the vibrating granular packing, which leads to an upward pressure on the base of the granular column in the tube, which is why the column ascends.

The scientists found that how fast and far the column rises depends on the tube size. Remarkably, the simulations showed that the height of the granular meniscus (the capillary height that the granular column reaches after a long time) is proportional to the inverse of the tube size. This is exactly the same behaviour as for liquid capillarity, although the driving forces in the two systems are so much different.

The physicists showed in their study that the same capillary effect can be produced by shaking the tube instead of the container, which opens up promising applications in the handling and transportation sectors. For example, particles could be pumped up from very large containers just by using granular capillarity. They are now studying the process in more depth to understand the effect of system and particle geometry.

###

Publication: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.218001

Dr. Eric Parteli | EurekAlert!

More articles from Physics and Astronomy:

nachricht Quantum optics allows us to abandon expensive lasers in spectroscopy
22.11.2017 | Lomonosov Moscow State University

nachricht Nano-watch has steady hands
22.11.2017 | University of Vienna

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: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Corporate coworking as a driver of innovation

22.11.2017 | Business and Finance

PPPL scientists deliver new high-resolution diagnostic to national laser facility

22.11.2017 | Physics and Astronomy

Quantum optics allows us to abandon expensive lasers in spectroscopy

22.11.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>