Effect of Microchannel Curvature on Water Droplet Dynamics in a Highly Viscous Flow

Abstract

This work is dedicated to the three-dimensional (3D) computational fluid dynamics (CFD) simulations of the microchannel curvature effect on water droplet dynamics in a highly viscous flow. Dynamics of 10 μm water droplets in bitumen medium flowing through U-shaped tubes of square-cross-section and of h = 40 μm width is investigated. The channel curvature radius R varies from 0.25h to 2h and the inlet Reynolds number Re in from 2 to 10. The coupled level-set and volume of fluid (CLSVOF) methods are combined with the adaptive mesh refinement (AMR) technique to accurately simulate a droplet flow regime. Different geometry performances are compared using onedimensional (1D) diagrams for integral flow characteristics and 3D visualization of the liquid−liquid interface. Flows in the vicinities of the convex and concave walls are found to control droplet deformation and breakup patterns. The results reveal that at Re in ≥ 7, the flow causes droplet breakup and temporary coalescence associated with the formation of long worm-shaped droplets. Differently positioned droplets for each Re in , bend radius, and interfacial tension cases are assessed individually. As a result, a droplet behavior map is developed based on local capillary and Reynolds numbers.