Dynamics of particle-particle collisions in a viscous liquid

Abstract

When two solid spheres collide in a liquid, the dynamic collision process is slowed by viscous dissipation and the increased pressure in the interparticle gap as compared with dry collisions. This paper investigates liquid-immersed head-on and oblique collisions, which complements previously investigated particle-on-wall immersed collisions. By defining the normal from the line of centers at contact, the experimental findings support the decomposition of an oblique collision into its normal and tangential components of motion. The normal relative particle motion is characterized by an effective coefficient of restitution and a binary Stokes number with a correlation that follows the particle-wall results. The tangential motion is described by a collision model using a normal coefficient of restitution and a friction coefficient that are modified for the liquid effects.

A contact model for normal immersed collisions between a particle and a wall

“…Joseph & Hunt (2004) examined oblique collisions between a particle and a wall. Later work by Yang & Hunt (2006) measured the coefficient of restitution for particle-particle collisions in a liquid and found a similar dependence on particle Stokes number. However, for Stokes numbers less than approximately 20 the authors observed that the target particle moved prior to impact due to the increase in hydrodynamic pressure as the impacting particle approached within a half a particle diameter.…”

Periodic saltation over hydrodynamically rough beds: aeolian to aquatic

“…Also, we indicate the modifications of these expressions to account for viscous dissipation in the way suggested by Yang and Hunt (2006), and already implemented to predict collisional sediment transport (Berzi & Fraccarollo 2013). In this case, the coefficients of restitution are assumed to depend on the Stokes number, so that…”

Enhanced upswing in immersed collisions of tethered spheres

“…1,2 Coupling between solid and liquid motions, however, modulates the influence of immersed collisions on the stress and energy balance of mixture flows. Studies of immersed particle-wall 3,4 and particle-particle collisions 5 have documented how particle rebound is damped by liquid viscosity. In particle-wall collisions, liquid vorticity has also been found to play a role.…”

“…3,5 To clarify the interplay between vortex motions and immersed collisions, we conducted experiments with both isolated and colliding spheres, in the pendulum configurations illustrated in Fig. 1.…”