Experimental study of solid-liquid-type transitions in vibrated granular layers and the relation with surface waves

Area of Science:

• Physics of granular materials
• Nonlinear dynamics
• Fluid dynamics

Background:

• Granular materials under vibration can exhibit complex behaviors, including fluidization and pattern formation.
• Understanding the transition from solid-like to liquid-like states is crucial for predicting granular flow and dynamics.

Purpose of the Study:

• To investigate the nature of transitions in vertically vibrated granular layers.
• To differentiate between various wave patterns and their underlying mechanisms.
• To characterize the conditions leading to the formation of bending waves.

Main Methods:

• Measurements of pressure and surface dilation in vibrated granular layers.
• Analysis of subharmonic bifurcations and wave pattern formation.
• Observation of a two-dimensional granular layer composed of photoelastic particles.

Main Results:

• A solid-liquid-type transition was observed at low excitation frequencies.
• This transition precedes the formation of standing wave patterns, linking them to fluid-like granular behavior.
• At higher frequencies, a distinct type of subharmonic bending wave was identified, involving minimal lateral grain transfer.
• These bending waves exhibit low amplitude and correspond to alternate temporal and spatial bending of the granular layer.

Conclusions:

• The study reveals distinct dynamic regimes in vibrated granular layers, governed by excitation frequency.
• Standing waves are associated with the fluid-like state of the granular layer.
• A novel type of bending wave, distinct from those involving bulk fluidization, has been characterized.