title: Study of the coalescence/splash threshold of droplet impact on liquid films and its relevance in assessing airborne particle release.
abstract: Impingement of droplets on surfaces occurs in many industrial and natural processes. The study of droplet break-up is fundamental in order to determine the potential sources of airborne contamination for scenarios of hazardous liquid falls such as dripping. There are very few data in the literature describing the case of impact of millimetre-size droplets. The purposes of this work were to study experimentally particle emission during the impact of droplets on a liquid film and to assess the use of coalescence/splash relations to predict airborne particle release. The results are described using dimensionless numbers taking into account the inertial, viscosity and surface tension forces. Experiments were carried out for Weber numbers between 62 and 1754 and for Ohnesorge numbers between 2.0×10(-3) and 1.5×10(-2). New results on coalescence/splash thresholds are obtained using highly sensitive aerosol measurement and allow a prediction concerning the presence or absence of airborne particles according to a threshold relation. Moreover, we propose a modification of the Cossali et al.'s relation in order to describe the coalescence/prompt splash threshold.
authors.affiliation: Laboratoire national de métrologie et d'essais - LNE (National Metrology Institute and Testing Laboratory), Chemistry and Biology Division, Air Quality and Gaz Flowmetering Department, 1 rue Gaston Boissier, 75724 Paris Cedex 15, France.
authors.forename: C
authors.initials: C
authors.lastname: Motzkus
authors.forename: F
authors.initials: F
authors.lastname: Gensdarmes
authors.forename: E
authors.initials: E
authors.lastname: Géhin
mesh_terms: D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D013499:Surface Properties; D013500:Surface Tension
chemical_list: D052638:Particulate Matter