Oblique collisions and rebound of spheres from a wetted surface

Abstract

Plastic and metal spheres were dropped from various heights onto a quartz disk covered with a thin layer of viscous oil and inclined at various angles with the horizontal. Rebound was observed only above a critical approach velocity, similar to that observed for head-on collisions when the disk is horizontal. The tangential component of the sphere's velocity is reduced only a small amount by the collision, owing to sliding lubrication/friction forces that also impart a small rotational velocity to the sphere. In contrast, the normal component of velocity is reduced substantially by viscous losses, and so the rebound angle of the sphere relative to the surface of the disk is smaller than the impact angle. The normal component of restitution and the rebound angle increase with the normal Stokes number based on the normal component of the impact velocity.

Theoretical Model for Normal Impact between Dry Sphere and Liquid Layer with Considerable Thickness

“…Moreover, from a qualitative perspective, Fig. 9 shares some similarities with those obtained previously for thin-layer impact (Davis et al, 2002;Kantak and Davis, 2004;Gollwitzer et al, 2012). Thus, the equation for "thick-layer impact" can be given in analogy with Eq.…”

Dynamics of particle-particle collisions in a viscous liquid

“…The correlation between the two parameters followed the same trend as the reported results for immersed normal on-wall collisions. The same trend was also observed by Kantak and Davis,6 who dropped a sphere obliquely onto a wall layered with a lubricant film. As for the tangential component of motion, Joseph and Hunt 7 first measured the tangential velocities, U it,cp and U rt,cp , at the contact point before and after an oblique collision.…”

“…6,7 Using the surface normal as reference, Joseph and Hunt 7 decomposed the sphere impact and rebound velocities at its center of mass and used the ratio of the normal velocities to define a normal effective coefficient of restitution e n =−U rn / U in . The normal particle Stokes number was also defined using the normal impact velocity.…”

A Brief Review of Viscosity Models for Slag in Coal Gasification

“…In many cases, this densification process is accelerated by the presence of a liquid phase (see Kingery and Berg 1955, Kingery 1959, Mehrabadi and Xu 1998, Xu and Mehrabadi 1997. The wetting parameter, or the wettability, traces its source to the study of Young (1805) who related the contact angle (a geometric parameter) to three thermodynamics quantities that account for the physical (interaction) properties of the contacting phases (see Barberis andCapurro 2008 andKantak andDavis 2004 for a discussion of this issue).…”