Gravitational Instabilities Article Published in PNAS and Featured in Popular Mechanics

This article, recently published in PNAS, shows how a combination of gas flow and vertical vibration can excite granular particles into a fluid-like state without gas bubbles traveling through them. In this excited state, gravitational instabilities mimicking conventional fluids form, such as the classic Rayleigh-Taylor instability and a bubble of lighter sand rising through heavier sand. The article describes the physical mechanisms underlying this phenomenon, which was initially confounding since surface tension does not exist between the two types of particles. It is anticipated that this understanding can be used to develop new process technologies and also be used to understand geological formations. A number of news outlets wrote about the finding, including Popular Mechanics.