Drop Fragmentation at Impact onto a Bath of an Immiscible Liquid

The impact of a drop onto a deep bath of an immiscible liquid is studied with emphasis on the drop fragmentation into a collection of noncoalescing daughter drops. At impact the drop flattens and spreads at the surface of the crater it transiently opens in the bath and reaches a maximum deformation, which gets larger with increasing impact velocity, before surface tension drives its recession. This recession can promote the fragmentation by two different mechanisms: At moderate impact velocity, the drop recession converges to the axis of symmetry to form a jet which then fragments by a Plateau-Rayleigh mechanism. At higher velocity the edge of the receding drop destabilizes and shapes into radial ligaments which subsequently fragment. For this latter mechanism the number N?We3 and the size distribution of the daughter drops p(d)?d?4 as a function of the impact Weber number We are explained on the basis of the observed spreading of the drop. The universality of this model for the fragmentation of receding liquid sheets might be relevant for other configurations.