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

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 Rein 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 one-dimensional (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 Rein ≥ 7, the flow causes droplet breakup and temporary coalescence associated with the formation of long worm-shaped droplets. Differently positioned droplets for each Rein, 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.