Tuned vibration waveforms unveil a key energy parameter for granular convection in fluidized beds

초록

Granular beds subjected to vertical mechanical vibration become fluidized and exhibit convection patterns, yet the influence of vibration energy input on the convection rate remains underexplored. Here, we demonstrate that a unified energy parameter ɛ, which encapsulates both velocity and acceleration characteristics of the vibration input, plays a decisive role in controlling convection rates. While keeping amplitude and frequency constant, vibration wave profiles were tuned using two geometric parameters: the fall/rise time ratio and the amplitude ratio. Through discrete element method (DEM) simulations, we identify a robust linear relationship between ɛ and the rising velocity of an intruder particle - a direct proxy for convection strength. This relationship persists across diverse waveform geometries, indicating that ɛ governs convection dynamics in fluidized beds. Experimental validation using polyvinyl chloride (PVC) beads and custom-designed vibration cams corroborates the simulation results. Our findings unveil a previously hidden control parameter for granular convection, offering new avenues for energy-efficient material processing and particle transport.

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