Coalescence Behavior of Viscous Droplets on Hydrophobic Fibers with Wettability Gradient

doi:10.3901/JME.260202

Abstract

Abstract: Fiber coalescence filters are widely applied in various industrial fields and are commonly used for separating liquid aerosols from gas streams. The coalescence and directional motion of viscous droplets on hydrophobic fibers with a wettability gradient are investigated using numerical methods. The volume of fluid(VOF) method and an enhanced dynamic contact angle model are utilized to investigate the influences of surface wettability gradient, droplet diameter, and viscosity. It is found that the droplet velocity along the fiber increases with the enhancement of the wettability gradient. The peak velocity arises when the rear edge of the droplet crosses the wettability boundary, and a larger contact angle on the high-contact-angle side results in a higher velocity. Dimensionless analysis shows that as the ratio of droplet to fiber diameter increases, the droplet velocity increases, but the rate of increase gradually decreases due to the constraint on spreading imposed by the curvature of the fiber surface. The mechanism of viscosity influence is analyzed through viscous dissipation rate. High-viscosity droplets exhibit relatively stable motion, while low-viscosity droplets move faster but with significant fluctuations. The findings provide theoretical support and design reference for the application of wettability gradients in high-efficiency oil mist filters.

Key words: wettability gradient, viscous droplet, coalescence, energy dissipation, volume of fluid

CLC Number:

TB13

FU Zeming, WU Huagen, XIONG Yanling, LIANG Mengtao. Coalescence Behavior of Viscous Droplets on Hydrophobic Fibers with Wettability Gradient[J]. Journal of Mechanical Engineering, 2025, 62(6): 391-399.

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URL: http://www.cjmenet.com.cn/EN/10.3901/JME.260202

http://www.cjmenet.com.cn/EN/Y2025/V62/I6/391

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