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Visualization of droplet merging in microchannels using micro-PIV

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Abstract

Flow visualization via micro-PIV has been conducted in order to investigate droplet-merging processes in microchannels. The dispersed-phase droplets seeded with 1-μm fluorescent particles are alternately generated in the cross-channel and merged downstream in a straight channel or in a divergent channel. Since droplet merging occurs within a millisecond, a high-speed camera capable of 6,000 fps is used to capture the images of the droplets and the tracer particles therein by observing through a 40× lens. These images reveal that droplets merge through a sequential process of attachment, drainage, interface coalescence, penetration or envelopment depending on the channel geometry. In the straight channel, where the droplets are confined by the channel walls, the rear droplet penetrates the front droplet at the instant of coalescence. However, when the droplets merge in the divergent channel, a strong vortex motion occurs while the rear droplet envelops the front one.

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Acknowledgments

This work was supported by grant no. KRF-2007-400-20070190 and also in part by grant no. KRF-0420-20070058 both from the Korea Research Foundation subsidized by the Ministry of Education, Science and Technology, Republic of Korea.

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Authors and Affiliations

  1. School of Mechanical and Aerospace Engineering, Seoul National University, Seoul, 151-744, Korea

    Byung-Ju Jin & Jung Yul Yoo

  2. Institute of Advanced Machinery and Design, Seoul National University, Seoul, 151-744, Korea

    Jung Yul Yoo

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  1. Byung-Ju Jin
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  2. Jung Yul Yoo
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Correspondence to Jung Yul Yoo.

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Jin, BJ., Yoo, J.Y. Visualization of droplet merging in microchannels using micro-PIV. Exp Fluids 52, 235–245 (2012). https://doi.org/10.1007/s00348-011-1221-0

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  • DOI: https://doi.org/10.1007/s00348-011-1221-0

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