Asynchronous bubble pinch-off pattern arising in fluidized beds due to jet interaction: A magnetic resonance imaging and computational modeling study

Abstract

Rapid magnetic resonance imaging is used to study the interaction between two gas jets injected into a 3D incipiently fluidized bed. At large separation distances and in cases with larger particles, bubbles pinch off from the two jets simultaneously with one another. At small separation distances with smaller particles, a jet grows at one orifice while a jet pinches off to form a bubble at the other orifice, resulting in bubbles pinching off the two jets nearly completely out-of-phase from one another. Discrete particle simulations coupled with computational fluid dynamics reproduce these two patterns. Simulations demonstrate that the asynchronous pattern emerges due to drag forces on the particles causing particle inertia dominate dissipation, causing motion of particles between the jets to become unstable. Specifically, when one jet is growing, it forces particles to move toward the neighboring jet, causing a bubble to break off from the neighboring jet.