Bouncing Mechanism of Two Identical Liquid Fuel Droplets upon Head-on Collision

Abstract

A physical model is developed to describe the phenomenon of bouncing which was observed in our previous two-body collision experiment for hydrocarbon liquid droplets. The repulsive forces acting between the colliding droplets are caused by the intervening air flow, which is analyzed on the basis of the lubrication theory taking into account the deformation of the droplets. The droplet bouncing takes place for a restricted range of the collision Weber number which depends on the droplet size and rheological properties. Its bounderies are identified in terms of the underlying elementary physics. In particular, the upper limit is proportional to the liquid viscosity, while the lower has little dependence, consistent with the experimental result.