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ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
A numerical investigation on concentrated emulsions in simple shear flow
Submission Author:
Raysa Gomes dos Santos , Buscando endereço.. , Brazil
Co-Authors:
Raysa Gomes dos Santos, Taygoara Oliveira
Presenter: Raysa Gomes dos Santos
doi://10.26678/ABCM.ENCIT2022.CIT22-0383
Abstract
This work explores the effects of droplet interactions in a concentrated emulsion under a simple shear flow. Our analysis considers a two-dimensional numerical domain where monodisperse Newtonian droplets flow under simple shear conditions in a Newtonian ambient fluid. The surface of the droplets is assumed to be free of surfactants, and we consider both phases with the same density and viscosity. The numerical methodology uses the projection method for pressure-velocity coupling and the Crank-Nicolson method for the temporal evolution of the momentum equation. Spatial discretization is carried out using second-order discretization and staggered grids. The level set method is used for tracking the interfaces of the droplets. High order essentially nonoscillatory (ENO) and weighted essentially nonoscillatory (WENO) conservative schemes, with a total variation diminishing (TVD) Runge-Kutta method, are used to discretize the level set equation. A method for generation of the initial position of the droplets, capable of setting up an emulsion of a given concentration, randomly spread in the ambient fluid is proposed. We study the flow for different droplet concentrations and capillary numbers. We found at low capillary numbers, the coalescence process increases as the volume fraction of the dispersed phase increases. On the other hand, for high capillary numbers, droplet merging decreases for any concentration range. They tend to slide over each other due to the decreased interfacial tension. In both cases, however, our results indicate that the coalescence rate could be higher than expected for the flow conditions, indicating that it is necessary to implement methods to avoid artificial droplet merging.
Keywords
concentrated emulsions, Level Set method, Coalescence, Finite Differences
