The impact of a single drop on a wetted solid surface

The impact of single drops on a thin liquid film was studied to understand the mechanism of secondary atomisation of sprays colliding on a wetted, cold, solid surface. To span a wide range of conditions various mixtures of water and glycerol were used. The use of Weber number, Ohnesorge number and n...

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Bibliographic Details
Published in:Experiments in fluids 1997-04, Vol.22 (6), p.463-472
Main Authors: COSSALI, G. E, COGHE, A, MARENGO, M
Format: Article
Language:English
Subjects:
Atomizing
Drops and bubbles
Empirical analysis
Exact sciences and technology
Film thickness
Fluid dynamics
Fundamental areas of phenomenology (including applications)
Morphology
Nonhomogeneous flows
Parameter identification
Physics
Solid surfaces
Surface roughness
Viscosity
Weber number
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Summary:The impact of single drops on a thin liquid film was studied to understand the mechanism of secondary atomisation of sprays colliding on a wetted, cold, solid surface. To span a wide range of conditions various mixtures of water and glycerol were used. The use of Weber number, Ohnesorge number and non-dimensional film thickness to describe the peculiarities of the phenomenon allowed to carry out the experiments under appropriate similarity conditions. The impact of millimetric drops was analysed in detail by photographic means, using both still photography to study impact morphology, and laser sheet visualisation to investigate secondary droplet formation. Two mechanisms of splash were identified, depending essentially on the liquid viscosity (Ohnesorge number), a parameter which appears to play an important role also in defining the splash morphology. A photographic documentation is annexed. The characteristic times of the crown formation, the non-linear evolution of cusps (jet formation) and the surface roughness influence are further discussed. The experimental results allow to propose an empirical correlation for the splashing/deposition limit, for a wide range of conditions, and a comparison to available previous works is presented. The influence of the film thickness and liquid viscosity on the splash is confirmed and quantified.
ISSN:0723-4864
1432-1114
DOI:10.1007/s003480050073