Droplet-droplet, droplet-particle, and droplet-substrate collision behavior

In this paper, we present the research findings on the collision outcomes of water droplets with solid particles and substrates made of metal with variable surface wettability. We constructed the maps of two collision regimes (agglomeration and stretching separation) showing the number and size of secondary droplets in the coordinate system of the Weber number and dimensionless impact parameter. The key parameters of droplets and particles were varied: sizes and velocities, impact angles, and wettability of the solid surface. Droplet-particle collision regimes were compared with the outcomes of droplet collision with other droplets and with a massive solid surface. Finally, we determined in which conditions these outcomes differed significantly and, on the contrary, were quite similar in terms of the number and size of secondary droplets. The results obtained are important for the development of secondary droplet atomization technologies.