(207e) Pattern Formation in Fluidized Beds and Vertically Vibrated Granular Layers: Similarities and Differences

Gas-solid fluidized beds can form dynamical patterns when fluidized with a pulsed flow under certain experimental conditions. In shallow 3D beds, the surface oscillates forming stripes, squares, and hexagons, with a length-scale that depends on the frequency of the pulsed flow. These structures are sub-harmonic and resemble those formed on the surface of vertically vibrated beds in vacuo, suggesting a common mechanism, namely, parametric resonance. In bubbling quasi-2D beds, the pattern formation manifests itself as regular bubble patterns, where bubbles are generated in alternating positions at every pulse and rise, forming vertical hexagonal configurations.

Pattern formation excels as a method to structure fluidized bed dynamics and has great potential to facilitate fluidized bed scale-up; however, it has remained highly unexplored and is far from being understood. Furthermore, opposite to pattern formation in vibrated systems in vacuo, which has been successfully simulated, computational fluid dynamics has not been able to reproduce the experimental patterns in fluidized beds so far [1].

In this contribution, we discuss our last insights on pattern formation in fluidized beds obtained by new experiments and simulations, and comparison with pattern formation in vibrated systems. Similarities and differences between these two systems, i.e., onset to the pattern, boundary effects, hysteresis, driving parameters, and transients, will be discussed.

[1] K. Wu, L. de Martín, L. Mazzei, and M.-O. Coppens. Submitted to Powder Technology