The importance of micro and macro scales in breakup and coalescence

This paper briefly reviews the status of knowledge of breakup and coalescence of fluid volumes, topological transitions that occur frequently in liquid/liquid and liquid/gas systems. Although many studies have been performed on both breakup and coalescence, significant questions remain unanswered concerning the dynamics of each process. A key difficulty is that, in most applications, die driving flow scales are macroscopic but the breakup or coalescence transition scales are microscopic such that non-continuum or molecular effects can play a role. A list of basic issues related to breakup and coalescence is given. Then, suggestions are made for experimental and computational research strategies that can address these issues.