Structured bubbling in vibrated gas-fluidized beds of binary granular particles: experiments and simulations

Area of Science:

• Fluidization dynamics
• Granular material science
• Particle mixing and segregation

Background:

• Mixing and segregation of granular particles are crucial in industrial, agricultural, and natural processes.
• Vertical vibration and upward gas flow are known methods for manipulating granular particle behavior.
• Previously observed structured bubbling in monodisperse particles under combined vibration and gas flow.

Purpose of the Study:

• To investigate structured bubbling in binary mixtures of granular particles with varying size and density.
• To determine the effect of structured bubbling on particle mixing compared to unstructured bubbling.
• To validate experimental findings with discrete particle simulations and identify limitations of continuum models.

Main Methods:

• Experimental investigation of binary granular mixtures under combined vertical vibration and upward gas flow.
• Discrete particle simulations (DPS) to model particle behavior and bubble dynamics.
• Continuum particle simulations for comparative analysis.

Main Results:

• Structured bubbling patterns were successfully formed in binary mixtures with similar minimum fluidization velocities.
• Structured bubbling induced effective mixing of particles irrespective of their initial size and density distribution.
• Gas flow alone generated unstructured bubbles, leading to particle segregation, contrasting with structured bubbling's mixing effect.

Conclusions:

• Combined vibration and gas flow, inducing structured bubbling, is a viable method for mixing granular binary mixtures.
• Discrete particle simulations qualitatively and quantitatively supported experimental observations of structured bubbling and mixing.
• Continuum simulations require further development to accurately predict mixing phenomena in structured bubbling scenarios.