Wall Migration and Shear-Induced Diffusion of Fluid Droplets in Emulsions
Steven D. Hudson
The spatial distribution of drops in multiphase flow through narrow passages is analyzed theoretically and experimentally. In simple shear between two plates, drops migrate away from the walls and concentrate towards the center of the gap. At steady state, this flux is balanced by shear-induced diffusion. By integrating the non-linear convective-diffusion equation, an analytical expression is obtained that gives the steady-state drop concentration as a function of a single dimensionless parameter. Larger drop size and capillary number (Ca), and smaller gap spacing and total concentration, favor migration towards the center. Typically, the migration effect is significant even when droplets are 100 times smaller than the gap. The relationship of gradient- and self-diffusivity of drops is discussed. Non-uniform concentration along the vorticity axis is also investigated briefly.
Wall Migration and Shear-Induced Diffusion of Fluid Droplets in Emulsions, Physics of Fluids, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=852077
(Accessed December 4, 2023)