Bag breakup of low viscosity drops in the presence of a continuous air jet

TL;DR

This study investigates the breakup of low viscosity drops in a horizontal air jet, focusing on the bag breakup regime, and develops a theoretical model that matches experimental data on the influence of Weber and Ohnesorge numbers.

Contribution

The paper provides a theoretical expression for the breakup Weber number boundary and confirms the exponential growth model of drop deformation through experiments.

Findings

Breakup boundary Weber number derived as $We=12(1+2/3Oh^2)$

Radial and bag dimensions grow exponentially with deformation

Dependence of deformation growth on $We$ is strong, on $Oh$ is weak

Abstract

This work examines the breakup of a single drop of various low viscosity fluids as it deforms in the presence of continuous horizontal air jet. Such a fragmentation typically occurs after the bulk liquid has disintegrated upon exiting the atomizer and is in the form of an ensemble of drops which undergo further breakup. The drop deformation and its eventual disintegration is important in evaluating the efficacy of a particular industrial process, be it combustion in automobile engines or pesticide spraying in agricultural applications. The interplay between competing influences of surface tension and aerodynamic disruptive forces is represented by the Weber number, $We$, and Ohnesorge number, $Oh$, and used to describe the breakup morphology. The breakup pattern considered in our study corresponds to that of a bag attached to a toroidal ring which occurs from $12 < We < 16$. We aim to address several issues connected with this breakup process and their dependence on $We$ and $Oh$ which have been hitherto unexplored. The $We$ boundary at which breakup begins is theoretically determined and the expression obtained, $We = 12(1 + 2/3Oh^2)$, is found to match well with experimental data available in literature. An exponential growth in the radial extent of the deformed drop and the streamline dimension of the bag is predicted by a theoretical model and confirmed by experimental findings. These quantities are observed to strongly depend on $We$. However, their dependence on $Oh$ is weak.