Collision of Two Liquid Wedges

1. INTRODUCTION Splashing following the collisions of liquids or granular materials is often observed in a variety of natural and engineering problems, such as plunging or breaking water waves, liquid droplets impacting on a free surface or a thin film of the same liquid, etc. Splashing leads to fluid fragmentation and the generation of drops and spray as well as fluid aeration. These phenomena involve the momentum and energy exchanges processes at the air-liquid interface, evaporation and air entrainment, cavity, bubbles, secondary drops, erosion, noise and sprays. A review of this of kind problem was presented by Yarin [1], which focused on drop impacts on thin liquid layers and dry surfaces. Kiger & Duncan [2] described the mechanism of air-entrainment, and Thoroddsen [3] centred the discussions on the initial stage of drop impact when liquid masses come into contact and coalesce. The current mathematical models may not be able to cover all the problems mentioned above. Nevertheless the formation of the splash jet and its effects on the main flow plays a major role in these phenomena. The present work aims to shed some light along this direction. Much of the work on splashing jet has mostly been based on experimental observation. Although this has greatly improved our understanding, it is still far from giving a thorough insight into this phenomenon, especially at the initial stage of impacts when physical parameters change rapidly.. Direct numerical simulations of splashing during droplets impacting on liquid layers were performed by Weiss [4] and Davidson [5] based on velocity potential theory with the boundary integral method and the surface tension was included. Their result showed that a splash jet might be formed, which moved close to the film, leading to the possibility of bubble entrapment. Incompressible Navier-Stokes equations with surface tension were solved numerically by Josserand & Zaleski [6]. The initial stage of a high speed droplet impact on a shallow water layer was investigated by