Segregation in a model system for tapped wet disks in two dimensions.

Area of Science:

• Physics
• Granular Materials Science
• Statistical Mechanics

Background:

• Size segregation in granular mixtures is a complex phenomenon influenced by particle interactions.
• Arch formation has been identified as a key mechanism in dry granular segregation.
• The role of capillary forces in wet granular segregation remains less understood.

Purpose of the Study:

• To investigate the influence of capillary forces on size segregation in a binary mixture of wet disks.
• To understand how humidity affects particle packing and segregation dynamics.
• To explore the specific role of capillary bridges in promoting the movement of larger particles.

Main Methods:

• A pseudo-dynamics algorithm was employed to simulate particle packing and tapping.
• A binary mixture of disks with two different sizes was used.
• Capillary forces were stochastically simulated using a sticking probability between particles.

Main Results:

• Humidity between grains was found to enhance the segregation process in binary mixtures.
• Capillary bridges play a significant role in segregation, beyond arch formation.
• Moisture promotes the upward movement of larger particles (intruders) even when arch formation alone would not favor it.

Conclusions:

• Capillary forces, induced by humidity, are a crucial factor in granular size segregation.
• The presence of moisture can overcome limitations imposed by arch formation in segregation processes.
• This study highlights the importance of considering inter-particle forces like capillary bridges in granular dynamics.