Anomalous descent of intruders in vibrated gas-fluidized granular materials.

Punch, Oscar J; Guo, Qiang; Gueye, Maty; Omidi, Javad; Jordan, Michael W; Sanghishetty, Jagan Mohan; Boyce, Christopher M · Phys Rev E · 2025

basic_science · Level V

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Abstract

The descent of dense intruder disks through granular material fluidized by vertical gas flow and vibration is investigated experimentally and computationally. Single intruders descend with a velocity which oscillates based on distance above the bottom of the system, which simulations show is due to a spatially dependent void fraction in the granular material changing the effective drag force on the intruder. Two vertically aligned intruders undergo a drafting-kissing-tumbling analog which forms because the bottom intruder decelerates due to particle compaction from the weight of the top intruder.