Computational Investigation of Drop Behavior and Breakup in Peristaltic Flow

The deformation and breakup behavior of liquid drops in the retropulsive jet produced by a peristaltic wave is investigated computationally. This study is motivated by recent experimental work on drop breakup in antral contraction wave flow in a model stomach. The goal is to expand the insights obtained in these experiments by considering a wider range of conditions, and to classify drop breakup more precisely. The computational geometry consists of a tube that is closed at one end; the peristaltic wave that deforms the tube boundary is modeled as a traveling wave moving toward the closed end. For these simulations, an OpenFOAM solver was developed which combines adaptive mesh refinement around deforming and moving drops with dynamic meshing techniques for domains with deforming boundaries. The new solver is first validated, where good agreement is found with experimental data. A parametric study is then performed where the interfacial tension, viscosity ratio, relative occlusion, and initial drop position are varied. The effects of these parameters on the drop's transit time, deformation, and breakup characteristics are determined. In particular, breakup regimes on graphs of capillary number versus viscosity ratio are found for each initial drop position and relative occlusion.