Viscous dynamics of drops and bubbles in Hele-Shaw cells: drainage, drag friction, coalescence, and bursting

TL;DR

This review explores the viscous behavior of drops and bubbles in Hele-Shaw cells, emphasizing how confinement alters scaling laws and introduces new physical regimes relevant for industrial applications.

Contribution

It highlights recent advances in understanding the effects of confinement on drop and bubble dynamics, emphasizing the role of viscosity and scaling laws in Hele-Shaw geometries.

Findings

Different scaling regimes emerge due to confinement effects.

Experimental and theoretical results show good agreement.

The review identifies open problems for future research.

Abstract

In this review article, we discuss recent studies on drops and bubbles in Hele-Shaw cells, focusing on how scaling laws exhibit crossovers from the three-dimensional counterparts and focusing on topics in which viscosity plays an important role. By virtue of progresses in analytical theory and high-speed imaging, dynamics of drops and bubbles have actively been studied with the aid of scaling arguments. However, compared with three dimensional problems, studies on the corresponding problems in Hele-Shaw cells are still limited. This review demonstrates that the effect of confinement in the Hele-Shaw cell introduces new physics allowing different scaling regimes to appear. For this purpose, we discuss various examples that are potentially important for industrial applications handling drops and bubbles in confined spaces by showing agreement between experiments and scaling theories. As a result, this review provides a collection of problems in hydrodynamics that may be analytically solved or that may be worth studying numerically in the near future.