A recent discovery explains a new family of gravitational instabilities in granular particles of different densities that are driven by a gas-channeling mechanism not seen in fluids. The team observed an unexpected Rayleigh-Taylor (R-T)-like instability in which lighter grains rise through heavier grains in the form of ‘fingers’ and ”granular bubbles, similar to the bubbles that form and rise in lava lamps.
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Source: ScienceDaily