Supercooled Water Drop Impact on Superhydrophobic Substrates with Various Roughness and Temperatures
Preventing supercooled water droplets impacting on low-temperature solid surfaces from adhesion and icing is of great importance to a wide variety of engineering applications,such as reducing ice accretion on aircrafts,power lines,industrial facilities and so on,which would cause significant damage.Superhydrophobic surface was proposed and studied to provide a good ice-phobic material,since its ability to reduce the liquid adhesion and minimize the contact time before the water could freeze.Many efforts have been made in understanding the static droplet icing at low temperature and the dynamic process of supercooled droplet collision with cold surfaces.However,the effect of the roughness of the superhydrophobic surfaces on the drop impact behaviors under low temperature needs further exploration.In this work,we investigate the dynamic behaviors of supercooled water droplets of-5℃ impacting on different superhydrophobic surfaces with various roughness and at the temperature ranging from -30℃ to -5℃.The outcomes of supercooled drop impact are compared with those of drop impact at the temperature from 0℃ to 15℃.The effect of surface roughness and temperature on the impalement and bouncing behaviors of drops is discussed.The employment of hierarchical roughness to fabricate superhydrophobic surfaces could repel impacting droplets more rapidly,compared with one-tier roughness,and pre vent drop adhesion even when the surface is cooled down to -30℃.The contact time on substrates with roughness smaller than 20μm experiences a slight change over a wide range of temperature,since most of the liquid moves above the roughness and the viscous effect is negligible.While the contact time on the substrates with submillimeter-scale roughness undergoes a sudden increase at temperature below -5℃,due to the deeper liquid penetration into the roughness and the larger viscous dissipation at lower temperature,which significantly deteriorates the anti-icing performance.The pancake bouncing disappears and the rupture of liquid film weakens when the substrates with submillimeter-scale roughness are cooled down to below -5℃.These findings are believed to provide a valuable strategy for the design of anti-icing materials under severe environment.
supercooled drop impact roughness temperature contact time
RUI Zhang HAO Pengfei ZHANG Xiwen HE Feng
Department of Engineering Mechanics Tsinghua University Beijing,100084,China
国际会议
重庆
英文
1-6
2017-09-25（万方平台首次上网日期，不代表论文的发表时间）