Droplets, Sprays and Aerosols: Vol. I. Principals of Atomization - Paperback

by Ashgriz (Author), Nasser Ashgriz (Author)

This book provides a theoretical description of the liquid atomization and spray formation. It is the first in series of books on droplets, sprays and aerosol.
The atomization process is a combination of several different liquid breakup processes. It involves of the formation of waves on the liquid surface, which are generated by a variety of effects, such as by the large relative velocity between the liquid and its surrounding gas. The waves may grow in amplitude, stretch out of the core liquid flow, and eventually breakup into cylindrical or sheet-like ligaments. Liquid ligaments may become unstable and breakup into droplets. Droplets may deform and breakup into smaller droplets by the drag forces or by collision with other droplets or solid surfaces.

The physical principal behind the above processes can be simplified into several liquid instability processes. These include instabilities of liquid sheets, jets, and droplets. These instabilities are mainly governed by Kelvin-Helmholtz, Rayleigh-Plateau, and Rayleigh-Taylor instabilities, which respectively come about due to a velocity difference between the liquid and its surrounding gas; due to capillary forces, and by the acceleration of one fluid onto the other.

Droplet-droplet collisions and droplet impact on solid surfaces are two other important processes that occur in sprays. Droplets may coalesce after collision forming larger droplets or breakup into smaller droplets. Phenomenological models are used to provide droplet sizes that emerge. Similarly, when a droplet impacts on a solid surface, it may spread, splash, or bounce off. Models for the relevant outcomes to atomization are provided for this process.

Finally, the atomization processes is modeled by combining various instability theories to obtain characteristic droplet sizes for different types of spray.