Document Type : Research Article
Assistant Prof., Chem. Eng. Dept., Iran Unv. Sci. &amp; Techn.
MA.chemical engineering،Iran University of Science and Technology
Assistant Professo.School of Mechanical Engineering, Biomechanics Iran University of Science and Technology
Droplet formation process is one of the most important steps in many microfluidic processes with biological and chemical applications. Factors affecting the droplet formation process include the geometry of the device, fluid properties, operating parameters and external forces. Since the construction of many microfluidic devices for geometric optimization required heavy costs, in this study, with the help of computational fluid dynamics technique, the droplet formation process is studied at different conditions. The purpose of this numerical study is to simulate the small droplets formation under the influence of an external electrical field. The innovative aspect of the present work is the study of parameters, which were not studied, in open literachar. Numerical simulation of the microchannel was performed in two-dimensional space. According to the flow physics, two liquid phases are assumed to be incompressible. Two geometric parameters of flow conversion region length and orifice length were investigated. The results of this study showed that for a length of 100 μm for the flow focusing region at high voltages, the droplet diameter can be reduced to less than 55 μm. The time difference between the formation of two consecutive drops for a length of 200 μm in this region at 300V increases to 0.178 seconds. It was shown that although the length of the orifice has no considerable effect on the droplet diameter, but at the length of 90 μm, droplets are formed after the orifice. It was also shown that when the distance between the electrodes is short, smaller droplets are formed due to the increase in electrical force applied to the common boundary of the two fluids. In fact, smaller droplets can be formed by selecting the appropriate configuration for the electrodes at lower voltages.