Atomization and Sprays, Vol.24, No.11, 977-997, 2014
A MODEL OF AN ATOMIZING DROP
This paper presents a two-level mathematical model that describes the aerodynamics of an evaporating mist around an atomizing spherical drop in a uniform air stream at large Weber numbers. The lower-level model describes the mechanics of daughter droplet formation at the parent drop surface. The model utilizes the concept of quasi-continuous, high-frequency periodic dispersion from the unstable part of the drop surface caused by the hydrodynamic instability of the gradient flow in conjugated boundary layers. The upper-level model reflects spatial aerodynamics of the evaporating spray being generated by atomizing drop. In this model, daughter droplets are assumed to behave as a multivelocity continuum and the ballistics of an axisymmetric evaporating mist are rendered as equations in dynamic four-dimensional space. The model rests on the following assumptions: the air-velocity field around a spherical drop is potential; the daughter droplets and their associated vapor do not influence the air flowfield; the initial velocity of newborn droplet is equal to that of the fastest unstable wave on the parent drop surface that produces it; the Ranz-Marshall model is appropriate for describing droplet evaporation. The variance in time of the spatial distributions of the breakaway droplets' mass, number density, and of the vapor density is processed and analyzed in video format. The detailed fields of the droplets' mean diameters are also obtained. Large vapor concentrations and a decreasing local gas-phase temperature are revealed.
Keywords:evaporating mist aerodynamics;breakaway droplet mechanics;mathematical modeling;numerical investigation