Vibration-induced granular segregation: a phenomenon driven by three mechanisms

Area of Science:

• Physics
• Materials Science
• Fluid Dynamics

Background:

• Granular materials exhibit complex behaviors under external stimuli.
• Vertical vibrations can induce particle segregation in granular beds.
• Understanding segregation mechanisms is crucial for industrial applications.

Purpose of the Study:

• To investigate the segregation dynamics of large spheres in a granular bed subjected to vertical vibrations.
• To systematically measure segregation rise times and analyze the influence of sphere properties and excitation parameters.
• To elucidate the dominant mechanisms driving segregation at different vibration frequencies.

Main Methods:

• Experimental setup involving a granular bed with large spheres.
• Systematic measurement of sphere rise times under varying density, diameter, and depth.
• Application of two distinct sinusoidal vertical vibration excitations.
• Analysis of segregation phenomena at low and high frequency regimes.

Main Results:

• At low frequencies, segregation is driven by inertia or convection, with dominance depending on relative density (>1 for inertia, <1 for convection).
• At high frequencies, convection is suppressed, and granular bed fluidization leads to segregation through buoyancy or sinkage.
• Rise times are systematically correlated with sphere properties and vibration parameters.

Conclusions:

• Vertical vibrations induce sphere segregation in granular beds through distinct mechanisms at low and high frequencies.
• Inertia and convection are key at low frequencies, while fluidization-driven buoyancy/sinkage dominates at high frequencies.
• The findings provide insights into the control of granular segregation via vibration parameters.