A recent magnetic resonance imaging study [Boyce et al., Phys. Rev. Fluids 4, 034303 (2019)] found that when two bubbles were injected side-by-side into an incipiently fluidized bed, below a critical injection volume, one bubble collapsed, while the other bubble survived, reaching the bed surface. Limitations in the experimental measurements left open questions about the apparent collapse: (1) did the bubble actually collapse or rather move out of the imaging plane and (2) if the bubble collapsed, was it due to gas transfer between bubbles or a preference for gas to channel toward the surviving bubble. Here we demonstrate that computational fluid dynamics–discrete element method (CFD-DEM) simulations can recreate this phenomenon. Simulation results reveal that the bubble does in fact collapse and that this collapse occurs because the slight size difference between the two bubbles causes gas flow to channel preferentially to the larger bubble, leaving the smaller bubble without enough gas flow to support its roof.

• Received 25 October 2019
• Accepted 11 February 2020

DOI:https://doi.org/10.1103/PhysRevFluids.5.034304