Microcanal com junção em T: estudo numérico bidimensional de padrões bifásicos de gotas usando o método campo de fase

Abstract

Two-phase flows are widely found in the most diverse practical applications, such as refrigeration systems, nuclear reactors, oil refineries, power generation units and many others. Among the equipment employing two-phase flows, microfluidic devices have been gaining more prominence lately. These devices have dimensions on the order of a few microns and are used in different branches of industry (pharmaceutical, electronics, cosmetics, medical, etc.). In this context, the importance of studying the characteristics of two-phase flows is highlighted, as well as the processes involved in them, such as the formation, breakup and coalescence of droplets/bubbles. This work aims to study the flow of a droplet in a two-dimensional microchannel with a T-shaped junction. The behavior of the droplet at the junction and the breakup or non-breakup regimes of the droplet are investigated, as well as the influence of parameters such as capillary number and droplet length on its flow. The study is conducted by means of numerical simulations performed in the commercial software COMSOL Multiphysics®, which uses the Finite Element Method to discretize the governing equations of a physical phenomenon. The Phase Field Method, available in COMSOL, is used to represent the interface between the continuous phase and the dispersed phase of the two-phase flow. In addition, local mesh refinement and adaptive mesh refinement techniques are applied in regions of greater interest in the domain, such as the walls and the interface between the fluids, in order to improve the accuracy of the numerical solution. Different cases were studied, each with a combination of capillary number and droplet length as it reaches the T-junction. Data such as the droplet breakup regime and the temporal evolution of the minimum thickness of the droplet neck at the junction were obtained. All results were compared with results present in the literature, in order to validate the methodology used. Finally, it was found that the numerical results obtained were in good agreement with the literature.