Researchers Create Bubbles of Sand for the First Time

Scientists from Columbia University just created bubbles of sand for the first time. The findings of the team’s study could have a significant impact on geology and pharmaceuticals.

To date, researchers are still struggling to understand the behavior of many small moving particles like sand. However, a better understanding of the movements of these granular materials could significantly improve many industries today.

For their study, the Columbia University researchers wanted to test if it is possible for bubbles to form in layers of sand with different densities – a characteristic common when mixing different liquids.

Granular materials can flow and take the shape of their containers like liquids. However, they can’t be fully considered liquids since pouring them out of their containers will create a pile instead of a puddle.

Bubbles of Sand

For their experiment, the scientists wanted to test a process called Rayleigh–Taylor instability, a behavior that occurs when lighter liquids push into heavier fluids. The most straightforward demonstration of this instability is when you put water and oil in one container.

Instead of liquids, the researchers use two kinds of sand, white sand and black sand, which they put in a see-through rectangular container. The black sand has larger and lighter grains as compared to the white sand. The scientists then shook the tank up and down using a special machine while the air flowed upward through the sand.

During the process, the scientists were surprised to observe as bubbles of black sand started to form on top of the heavier white sand. The behavior resembled the Rayleigh–Taylor instability, an exciting discovery for the scientists since the experiment didn’t include liquids.

Chris Boyce, one of the researchers, explained:

“We have found a granular analog of one of the last major fluid mechanical instabilities. While analogs of the other major instabilities have been discovered in granular flows in recent decades, the R-T instability has eluded direct comparison.

Our findings could not only explain geological formations and processes that underlie mineral deposits, but could also be used in powder-processing technologies in the energy, construction, and pharmaceuticals industries.”