液滴撞击超疏水—亲水混合表面的动态行为特性
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摘要
对液滴撞击普通表面、疏水表面、疏水—亲水混合表面的行为进行可视化观测,对比研究不同撞击表面的动力学特性,分析表面润湿性以及撞击速度对撞击行为的影响.疏水部分接触角选取115°、135°和150°.液滴撞击不同的表面,均会发生铺展、回缩、反弹或破碎行为.液滴撞击疏水表面的速度越大,表面的铺展因子越大,但不会影响最大铺展时间(3 ms).当液滴以2.43 m/s的速度撞击超疏水表面时,铺展因子可达3.43.研究发现,液滴撞击超疏水—亲水混合表面未发生反弹,且撞击速度越大,接触角越大,液滴撞击产生的液指越多,断裂产生的次生小液滴越多.结果表明,超疏水—亲水混合条纹可以减小单个液滴的体积,减少液滴的二次回弹.
The behavior of a single water droplet impacting on different surfaces is observed by high-speed camera,including bare surface,hydrophobic surface and hydrophobic-hydrophilic surface. Besides,the dynamic characteristics of droplet impacting on different surfaces are studied comparatively,so that how the impacting speed and wettability affect the behavior can be analyzed with different contact angles(115°,135°,150°). It is found that the water droplet spreads,retracts,rebounds or smashes in each dynamic process. The spread factor increases with the higher speed while the spreading time(3 ms) has no change. When the velocity of droplet is 2.43 m/s,the spreading factor is up to 3.43. The study shows that the rebound behavior of droplet impacting on the hydrophobic-hydrophilic surface does not happen. Moreover,more satellite droplets are produced as the contact angle becomes bigger and the speed becomes higher. In addition,the superhydrophobic-hydrophilic surfaces contribute to decreasing in volume of single droplet after retraction behavior.
The behavior of a single water droplet impacting on different surfaces is observed by high-speed camera,including bare surface,hydrophobic surface and hydrophobic-hydrophilic surface. Besides,the dynamic characteristics of droplet impacting on different surfaces are studied comparatively,so that how the impacting speed and wettability affect the behavior can be analyzed with different contact angles(115°,135°,150°). It is found that the water droplet spreads,retracts,rebounds or smashes in each dynamic process. The spread factor increases with the higher speed while the spreading time(3 ms) has no change. When the velocity of droplet is 2.43 m/s,the spreading factor is up to 3.43. The study shows that the rebound behavior of droplet impacting on the hydrophobic-hydrophilic surface does not happen. Moreover,more satellite droplets are produced as the contact angle becomes bigger and the speed becomes higher. In addition,the superhydrophobic-hydrophilic surfaces contribute to decreasing in volume of single droplet after retraction behavior.
引文
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[2]WORTHINGTON A M.On the forms assumed by drops of liquids falling vertically on a horizontal plate[J].Proceedings of the royal society of London,1876,25:261-272.
[3]李栋,王鑫,高尚文,等.单液滴撞击超疏水冷表面的反弹及破碎行为[J].化工学报,2017,68(6):2473-2482.LI D,WANG X,GAO S W,et al.Rebounding and splashing behavior of single water droplet impacting on cold superhydrophobic surface[J].CIESC journal,2017,68(6):2473-2482.(in Chinese)
[4]ZHANG R,HAO P F,ZHANG X W,et al.Supercooled water droplet impact on superhydrophobic surfaces with various roughness and temperature[J].International journal of heat and mass transfer,2018,122:395-402.
[5]杨宝海,王宏,朱恂,等.速度对液滴撞击超疏水壁面行为特性的影响[J].化工学报,2012,63(10):3027-3033.YANG B H,WANG H,ZHU X,et al.Effect of velocity on behavior of droplet impacting superhydrophobic surface[J].CIESCjournal,2012,63:3027-3033.(in Chinese)
[6]PATIL N D,BHARDWAJ R,SHARMA A.Droplet impact dynamics on micropillared hydrophobic surfaces[J].Experimental thermal and fluid science,2016,74:195-206.
[7]LIU Y,MOEVIUS L,XU X.Pancake bouncing on superhydrophobic surfaces[J].Nature physics,2014,10(7):515-519.
[8]LECLEAR S,LECLEAR J,ABHIJEET,PARK K C,et al.Drop impact on inclined superhydrophobic surfaces[J].Journal of colloid and interface science,2016,461:114-121.
[9]JIN Z Y,WANG Z N,SUI D Y,et al.The impact and freezing processes of a water droplet on different inclined cold surfaces[J].International journal of heat and mass transfer,2016,97:211-223.
[10]YIN C C,WANG T Y,CHE Z Z,et al.Oblique impact of droplets on microstructured superhydrophobic surfaces[J].International journal of heat and mass transfer,2018,123:693-704.
[11]LI X L,ZHANG L,MA X W,et al.Dynamic characteristics of droplet impacting on prepared hydrophobic/superhydrophobic silicon surfaces[J].Surface and coatings technology,2016,307:243-253.
[12]JOSSERAND,CHRISTOPHE,THORODDSEN S T.Drop impact on a solid surface[J].Annual review of fluid mechanics,2016,48:365-391.
[13]刘冬薇,宁智,吕明,等.液滴撞击超疏水壁面反弹及破碎行为研究[J].计算力学学报,2016,33(1):107-113.LIU D W,NING Z,LM,et al.Rebounding and splashing behavior of water droplet impacting on superhydrophobic surface[J].Chinese journal of computational mechanics,2016,33:107-113.(in Chinese)
[14]YAN J H,YANG K,ZHANG X B,et al.Analysis of impact phenomenon on superhydrophobic surfaces based on molecular dynamics simulation[J].Computational materials science,2017,134:8-16.
[15]李西营,高丽,刘勇.超疏水表面上液滴撞击动力学的研究[J].广州化工,2011,39(22):39-41.LI X Y,GAO L,LIU Y.Study on the dynamics of water droplet impacting superhydrophobic surface[J].Guangzhou chemical industry,2011,39(22):39-41.(in Chinese).