Dynamics of grain ejection by sphere impact on a granular bed

Stéphanie Deboeuf (1) , Philippe Gondret (2) , Marc Rabaud (2)

1 LPS - Laboratoire de Physique Statistique de l'ENS
2 FAST - Fluides, automatique, systèmes thermiques

The dynamics of grain ejection consecutive to a sphere impacting a granular material is investigated experimentally and the variations of the characteristics of grain ejection with the control parameters are quantitatively studied. The time evolution of the corona formed by the ejected grains is reported, mainly in terms of its diameter and height, and favourably compared with a simple ballistic model. A key characteristic of the granular corona is that the angle formed by its edge with the horizontal granular surface remains constant during the ejection process, which again can be reproduced by the ballistic model. The number and the kinetic energy of the ejected grains is evaluated and allows for the calculation of an effective restitution coefficient characterizing the complex collision process between the impacting sphere and the fine granular target. The effective restitution coefficient is found to be constant when varying the control parameters.

Mots clés: Granular; Impact; Ejection; Crater

Domaines: Matière Molle [cond-mat.soft]; Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Stéphanie Deboeuf, Philippe Gondret, Marc Rabaud. Dynamics of grain ejection by sphere impact on a granular bed. 2008. ⟨hal-00311419v3⟩