Influence of droplet clustering in sprays on liquid deposition rate on spherical targets

Abstract

[EN] The origin of temporal fluctuations of liquid mass deposition rates, obtained from a spray of droplets impinging on a solid spherical target, was investigated by correlation with droplet clusters in the spray. The droplet clusters were quantified using a Voronoi analysis on instantaneous images of the droplets, to obtain the number of droplet clusters, the area of the clusters and the number of droplets in each cluster. It was found that the normalised area of the droplet clusters had a distribution with a peak around 10-1 and a right tail which followed a power law of exponent -1.8. As the number density of the droplets inside the clusters increased, the temporal fluctuations of the liquid mass deposition rates increased, as a greater variation of droplet sizes impinged the target. However, as the standard deviation of the distribution of the normalised droplet cluster areas was increased, the temporal fluctuations in the liquid mass deposition rates reduced, as variations to the droplet number density and droplet sizes inside the clusters were averaged out.