Normal and oblique impacts between smooth spheres and liquid layers: Liquid bridge and restitution coefficient

作者：Ma, Jiliang; Liu, Daoyin^*; Chen, Xiaoping

来源：Powder Technology, 2016, 301: 747-759.

DOI：10.1016/j.powtec.2016.07.001

• Wet impact
• Liquid bridge
• Restitution coefficient
• Stokes number

Detailed understanding of individual collision mechanics of particles in the presence of liquid is crucial for modeling wet particle flows that are omnipresent in nature and various industries. Our early work (Ma et al., 2013) preliminarily characterized the oblique impacts between rough-surface sphere and liquid layers with wide-ranging impact parameters by means of restitution coefficients. The current paper deepens the early work by performing both normal and oblique impacts between smooth-surface collision bodies, focusing on the collision details such as liquid bridge configuration, liquid layer morphology as well as the restitution coefficients with the aid of improved experimental setup. Different from static liquid bridge or the dynamic bridge with constant liquid volume, the formation and development of impact-induced liquid bridge is greatly influenced by the inertia of surrounding liquid that could be represented by liquid Reynolds number. Moreover, liquid inertia is also found to affect the total kinetic energy reduction of spheres through changing the layer morphology, thus having to be considered during theoretical modeling. Liquid bridge force contributes a lot to the energy reduction of rebounding sphere in the normal direction, while has little effects in the tangential direction. For the oblique impacts of smooth spheres with thin liquid layers, no matter how viscous the liquid is, the tangential restitution coefficients are always maintained at higher values than dry impact for the lubrication effect exerted by liquid. The effect gradually weakens as the layer thickness increases. The lubrication effect is not observed for rough-surface impacts owing to the additional energy reduction caused by the physical interaction between surface asperities. Due to the significant role of layer thickness in the energy dissipation process, the liquid drag force arising during the impacts with considerable thickness has to be considered in the development of theoretical models for restitution coefficients.

• 出版日期2016-11
• 单位东南大学