Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Numerical Investigation of Droplet Deformation and Breakup in T-Junction Microfluidics
Submission Author:
Juan Linhares Barbosa , DF
Co-Authors:
Juan Linhares Barbosa, Paulo Henrique Neves Pimenta, Taygoara Oliveira
Presenter: Juan Linhares Barbosa
doi://10.26678/ABCM.COBEM2023.COB2023-0690
Abstract
Emulsions are important to numerous industrial processes in the food, pharmaceutical, chemical, and other industries. In particular, the flow of droplets in T-junctions has special relevance for processes of mono-disperse emulsion generation in microfluidics devices. In this work, we present an analysis of the flow, deformation, and breakup of a single droplet in a T-junction. The model considers the Navier-Stokes equation for incompressible transient flow and captures the interface using the Level Set method. We used the Projection method to solve the pressure-velocity problem, using a Crank-Nicolson scheme to evolve the solution in time. To solve the Level Set equation, a TVD Runge-Kutta was utilized for temporal evolution. For spatial discretization, we employed an high-order upwind scheme that combines ENO and WENO techniques to approximate the derivatives. To validate our approach, we compared our results with references from literature for both the inlet and outlet regions of the T-junction. We found that the deformation of spherical droplets in the main channel of the T-junction is influenced by the droplet's size and the capillary number. When the aspect ratio of the droplet, defined as the ratio between the droplet's radius and the channel's width, is small, the droplet experiences small deformations due to the fact that these droplets are too far from the channel walls to experience significant shear tension imposed by the flow. However, increasing the aspect ratio up to 0.5 leads to significant deviation from the spherical shape. We showed that deformation is reduced by decreasing the capillary number, which increases the interfacial tension. When the aspect ratio exceeds 0.5, droplets lose their spherical shape and become elongated. We then evaluated the mean velocity of elongated droplets along the main channel as a function of the capillary number. Our findings indicate that for larger capillary numbers, the droplet's mean velocity was greater due to the reduced viscous tension resisting the flow. In terms of the breakup process, we observed that more elongated droplets, as measured by their relaxed length, tend to break into two smaller droplets for larger capillary numbers, while less elongated droplets or those with smaller capillary numbers tend not to break. In summary, we found that the capillary number is an essential parameter that governs droplet’s behavior along the main channel and during the breakup process. Therefore, our results provide a useful tool for understanding and controlling emulsions in microfluidic devices, benefiting industrial processes.
Keywords
droplet breakup, T-junction, Level Set method, Microfluidics, Emulsions
