Behavior of microdroplets in diffuser/nozzle structures |
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Authors: | Jing Liu Yit Fatt Yap Nam-Trung Nguyen |
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Affiliation: | (1) School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore |
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Abstract: | This paper investigates the behavior of microdroplets flowing in microchannels with a series of diffuser/nozzle structures.
Depending on the imposed flow direction, the serial structures can act either as a series of diffusers or nozzles. Different
serial diffuser/nozzle microchannels with opening angles ranging from 15° to 45° were considered. A 2D numerical model was
employed to study the dynamics of the microdroplet during its passage through the diffuser/nozzle structures. The deformation
of the microdroplet was captured using a level set method. On the experimental front, test devices were fabricated in polydimethylsiloxane
using soft lithography. T-junctions for droplet formation, diffuser/nozzle structures and pressure ports were integrated in
a single device. Mineral oil with 2% w/w surfactant span 80 and de-ionized water with fluorescent worked as the carrier phase
and the dispersed phase, respectively. The deformation of the water droplet and the corresponding pressure drop across the
diffuser/nozzle structures were measured in both diffuser and nozzle configurations at a fixed flow rate ratio between oil
and water of 30. The results show a linear relationship between the pressure drop and the flow rate. Furthermore, the rectification
effect was observed in all tested devices. The pressure drop in the diffuser configuration is higher than that of the nozzle
configuration. Finally, the pressure measured results with droplet and without droplet were analyzed and compared. |
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Keywords: | Microdroplet Diffuser/nozzle T-junction Microchannel |
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