Pattern formation in fluidized and vibrated beds: experimental and computational insights

Gas-solid fluidized beds can form dynamical patterns when fluidized with a pulsed flow (1). This phenomenon excels as a method to structure fluidized bed dynamics and has great potential to facilitate fluidized bed scale-up (2,3) and validate computational fluid-dynamics models (4); however, it has remained highly unexplored since first discovered and it is far from being understood. Moreover, Computational Fluid Dynamics (CFD) have not been able so far to clearly reproduce the experimental patterns (4,5), even though discrete element model (DEM) studies suggest some organization of the bubbles (5). Patterns appear as a result of the collective behavior of granular matter when subject to an oscillating excitation, and can also be observed in vertically vibrated beds (6). In bubbling quasi-2D beds, patterns manifest themselves as hexagonal bubble configurations, where bubbles are generated in alternating positions at every pulse. In shallow 3D beds, independently of the type of excitation¾vibration or pulsed flow¾the surface is decorated with stripes and squares (Fig. 1) in which the characteristic length-scale decreases with the frequency of the oscillating force. Contrary to pattern formation in fluidized beds, patterns in vibrated systems have been extensively studied. The knowledge developed in this field can be used as a basis to understand the behavior of fluidized granular matter. In this contribution, we show the first successful CFD simulation of an experimental bubble pattern in a gas-solid fluidized bed, which was obtained with DEM (Fig. 2). We also discuss our last insights about pattern formation in fluidized beds obtained by comparing experimental pattern formation in vibrated and fluidized systems. Gas-solid fluidized beds can form dynamical patterns when fluidized with a pulsed flow (1). This phenomenon excels as a method to structure fluidized bed dynamics and has great potential to facilitate fluidized bed scale-up (2,3) and validate computational fluid-dynamics models (4); however, it has remained highly unexplored since first discovered and it is far from being understood. Moreover, Computational Fluid Dynamics (CFD) have not been able so far to clearly reproduce the experimental patterns (4,5), even though discrete element model (DEM) studies suggest some organization of the bubbles (5). Patterns appear as a result of the collective behavior of granular matter when subject to an oscillating excitation, and can also be observed in vertically vibrated beds (6). In bubbling quasi-2D beds, patterns manifest themselves as hexagonal bubble configurations, where bubbles are generated in alternating positions at every pulse. In shallow 3D beds, independently of the type of excitation¾vibration or pulsed flow¾the surface is decorated with stripes and squares (Fig. 1) in which the characteristic length-scale decreases with the frequency of the oscillating force. Contrary to pattern formation in fluidized beds, patterns in vibrated systems have been extensively studied. The knowledge developed in this field can be used as a basis to understand the behavior of fluidized granular matter. In this contribution, we show the first successful CFD simulation of an experimental bubble pattern in a gas-solid fluidized bed, which was obtained with DEM (Fig. 2). We also discuss our last insights about pattern formation in fluidized beds obtained by comparing experimental pattern formation in vibrated and fluidized systems. Gas-solid fluidized beds can form dynamical patterns when fluidized with a pulsed flow (1). This phenomenon excels as a method to structure fluidized bed dynamics and has great potential to facilitate fluidized bed scale-up (2,3) and validate computational fluid-dynamics models (4); however, it has remained highly unexplored since first discovered and it is far from being understood. Moreover, Computational Fluid Dynamics (CFD) have not been able so far to clearly reproduce the experimental patterns (4,5), even though discrete element model (DEM) studies suggest some organization of the bubbles (5). Patterns appear as a result of the collective behavior of granular matter when subject to an oscillating excitation, and can also be observed in vertically vibrated beds (6). In bubbling quasi-2D beds, patterns manifest themselves as hexagonal bubble configurations, where bubbles are generated in alternating positions at every pulse. In shallow 3D beds, independently of the type of excitation¾vibration or pulsed flow¾the surface is decorated with stripes and squares (Fig. 1) in which the characteristic length-scale decreases with the frequency of the oscillating force. Contrary to pattern formation in fluidized beds, patterns in vibrated systems have been extensively studied. The knowledge developed in this field can be used as a basis to understand the behavior of fluidized granular matter. In this contribution, we show the first successful CFD simulation of an experimental bubble pattern in a gas-solid fluidized bed, which was obtained with DEM (Fig. 2). We also discuss our last insights about pattern formation in fluidized beds obtained by comparing experimental pattern formation in vibrated and fluidized systems. Please click Additional Files below to see the full abstract