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Updated: May 31, 2026
11:51
Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions
Published on: February 22, 2018
Droplet and cluster formation in freely falling granular streams
Scott R Waitukaitis1, Helge F Grütjen, John R Royer
1Department of Physics, University of Chicago, Chicago, Illinois 60637, USA.
Summary
Particle beams can now probe macroscopic systems like granular media. Simulations reveal how collision energy and attractive forces influence grain stream behavior, leading to droplet formation.
Area of Science:
- Physics
- Granular Mechanics
- Complex Systems
Background:
- Particle beams are established tools for atomic and molecular interactions.
- Recent experiments show granular streams exhibiting liquid-like breakup.
- Macroscopic systems offer new frontiers for particle beam investigations.
Purpose of the Study:
- Investigate granular stream evolution using molecular dynamics simulations.
- Understand how nanoscale collision details affect macroscopic stream behavior.
- Map the spectrum of behaviors from gas-like jets to liquid-like droplet formation.
Main Methods:
- Molecular dynamics simulations of dense macroscopic sphere streams.
- Parameterization by coefficient of restitution and cohesive interaction strength.
- Development of an energy balance model for droplet formation.
Main Results:
- Inelastic collisions collimate the granular stream.
- Attractive interactions drive structure formation and aggregation.
- Observed gas-like, liquid-like, and a novel intermediate aggregate-forming regime.
Conclusions:
- Granular stream behavior is strongly linked to velocity gradients from free fall.
- The proposed energy balance model explains droplet formation.
- Results quantify the role of attractions in cooling granular streams and align with experimental data.
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