Spray deposition: the importance of droplet impact phenomena

Abstract

Spray deposition is governed by a wide variety of different physical processes. These range from atomization, acceleration and transport of droplets, via heat transfer in the spray region, to the impact and solidification of droplets on a substrate. While some of these aspects have received a great deal of attention in the past, the phenomena of droplet impact are still not well understood and subject to many investigations. The particular processes occurring during droplet impact are important both, to the final characteristics of the sprayed product and to the manufacturing costs. For example, the entrainment of gas bubbles or the rupture of the metal melt by cavitation may result in spray products of minor quality. Furthermore, splashing drops can produce a large number of splash droplets that are carried away by the gas flow, thus leading to an additional source of overspray. These and other phenomena of droplet impact, and their significance to spray deposition processes will be discussed.