Coefficient of restitution for wet particles.

Area of Science:

• Fluid dynamics
• Particle physics
• Surface science

Background:

• The coefficient of restitution (COR) quantifies energy loss during particle collisions.
• Understanding liquid film effects on particle bounce is crucial for various industrial and natural processes.

Purpose of the Study:

• To experimentally investigate how a liquid film influences the COR of freely falling particles.
• To determine the key parameters governing COR in particle-wet surface interactions.

Main Methods:

• Freely falling particles were traced bouncing on a wet surface.
• Experiments varied impact velocity, particle properties, and liquid properties.
• Analysis involved dimensionless numbers characterizing inertial, viscous, and surface forces.

Main Results:

• The COR is significantly influenced by the presence of a liquid film.
• COR depends on impact velocity, particle, and liquid characteristics.
• In regimes beyond lubrication theory, the film thickness to particle size ratio is a critical determinant of COR.

Conclusions:

• Liquid films reduce the coefficient of restitution during particle bounces.
• Dimensionless numbers effectively describe the complex interplay of forces.
• Film thickness relative to particle size is a vital parameter for predicting COR in non-lubrication regimes.