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Sand is a difficult material to understand. In a recent study, engineers have demonstrated a recently observed instability of this granular particle: the formation of "sand bubbles". ( Nici Keil | pixabay )
For a long time, the behavior of moving granular particles such as sand has been a mystery even for scientists.
When in motion, the sand is strangely similar to the liquid, as in moving sand dunes and avalanches, among other events. However, understanding the physics of sand flow remains elusive.
Today, engineers gain valuable knowledge of granular particles through a discovery that Chris Boyce, an associate professor at Columbia Engineering, describes as "transformational," according to a university report.
Sand Bubbles Form In New Experiment
In a study published in the journal Proceedings of the National Academy of Sciencesresearchers are introducing a new family of gravitational instabilities into granular particles of different densities. Surprisingly, the mechanism looks much more like a gas than a liquid.
The results show Raleigh-Taylor instability, which occurs when lighter grains pass through heavier grains in the form of "fingers" and "bubbles". This type of instability occurs when two fluids of different densities that do not mix interact, such as water and oil. Until the new study, this behavior has never been observed in two dry granular particles and solids.
For the first time ever, researchers found lighter sand bubbles that rose into thicker sand when both types of sand were exposed to vertical vibration and rising gas flow.
This is like air bubbles and oil bubbles rising in the water because these particles do not mix with water. In the case of sand, however, both types of sand mix.
"We found a granular analogue of one of the last great instabilities of fluid mechanics," explained Boyce, one of the authors of the study. "While analogies of other major instabilities have been discovered in granular flows in recent decades, the instability RT has not been directly compared.Our results could not only explain formations and geological processes underlying mineral deposits, but they could also be used in the treatment of powder technologies in the energy, construction and pharmaceutical sectors. "
Experience and its impact on science
To achieve their results, the researchers used experimental and computer modeling to demonstrate that gas channeled through lighter sand and created bubbles. The instability of Raleigh-Taylor is due to the collision between the upward thrust of the lighter particles combined with the gas pipeline and the downward force of the heavier particles, a behavior that the liquid particles do not exhibit.
In a report from Gizmodo, Boyce said that while the configuration of the experiment may be highly unlikely in the real world, it could be used in industrial environments on chemicals supposed to react to each other.
The team is eager to see the potential impacts of their discoveries on the geological sciences, as these types of instabilities can enlighten us on the formation of the many structures of the planet during the course of history.
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