Particle impact on a cohesive granular media

Area of Science:

• Granular physics
• Particle impact dynamics
• Cohesive granular materials

Background:

• Understanding particle impact on granular beds is crucial for various industrial and natural processes.
• The role of inter-particle cohesion, particularly due to liquid bridges, in modifying impact outcomes is not fully understood.

Purpose of the Study:

• To numerically investigate the splash process resulting from a particle impacting a cohesive granular packing.
• To quantify the influence of impact velocity, capillary strength (Γ), and liquid content (Ω) on particle ejection.

Main Methods:

• Two-dimensional discrete element method (DEM) simulations were employed.
• Cohesion was modeled using short-range attractive forces simulating liquid bridges.
• Analysis focused on the number of ejected particles as a function of impact parameters.

Main Results:

• The splash process is significantly altered when the dimensionless cohesion number (Co) exceeds a critical value near unity.
• Above this cohesion threshold, particle ejection is triggered above a specific impact Froude number (Fr).
• This threshold Froude number scales with capillary strength (Γ) and liquid content (Ω) as Γ^(1/2)Ω^(1/6).
• The number of splashed particles shows a linear dependence on the impact Froude number, similar to cohesionless cases, once the threshold is surpassed.

Conclusions:

• Inter-particle liquid bridges play a critical role in governing particle ejection during impact events.
• The study provides quantitative relationships for the threshold conditions and scaling laws governing splash dynamics in cohesive granular materials.
• Findings offer insights into phenomena like erosion, powder handling, and planetary surface impacts.