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Droplet passing through a film is a ubiquitous phenomenon in nature, such as a rain drop impacting on a rain bubble in paddle and pouring beer onto the beer foam, etc. This phenomenon has not been sufficiently investigated and many interfacial interaction mechanisms are still unknown. In this paper, the passing modes and the kinematics of a droplet impacting on a soap film are studied with the help of a high-speed cameral. The impacting Weber number of the droplet varies from 10 to more than 350. The droplet position and velocity are extracted from the video by a self-designed Matlab codes. Experimental results show that the droplet may pass through the soap film in five modes, i.e., bouncing, bagless packaging, package peeling, bag packaging, and instaneous coalescence. A " drop-cushion-shell”-type compound droplet can be formatted in bag-[We ∈ (10.8, 60)] and bagless [We ∈ (120, 240)] packaging mode, while in the package peeling [We ∈ (60, 120)] and coalescence [We ∈ (240, 350)] mode it will form single phase droplets, however, with the surface coated with a soap solution layer (original soap film). Although compound droplets have three surfaces, i.e., the droplet’s original surface and the inner and outer surface of the soap film, the apparent surface tension for the bagless-packed droplet is just that of the soap solution, while for the bag-packed droplet it is the sum of the three surface tensions. The outer shell of the compound droplet may peel off and eject a bubble when the Weber number is in the certain range (We ∈ (60, 120) for droplet with D0 = 3.0 mm), the lower limit decreases and the upper limit increases with the increase of the initial diameter of the droplets and thus expands the bubble-shooting range. The droplet performs a free fall motion, however, it is interfered by the soap film. The droplet can be stopped and rebounded when We < 10.8, and penetrate the film and start another free fall when We > 10.8. The velocity loss before and after the penetration decrease with impact velocity increasing, hence the motion of the higher We droplet is less retarded by the soap film, the motion curve approaches to the free fall curve. The approaching is not a linear but an accelerating behavior. -
Keywords:
- droplet /
- soap film /
- impact /
- passing modes /
- bubble shooting
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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图 1 液滴撞击肥皂膜实验台架示意图
Figure 1. Schematic diagram of the experimental platform.
图 2 液滴的反弹与穿越
Figure 2. Rebounding and penetration of droplets.
图 3 穿越后复合液滴(D0 = 3.0 mm)的直径振荡曲线与振荡周期 (a)液滴振荡; (b)振荡周期实验值与理论曲线对比
Figure 3. Droplet (D0 = 3.0 mm) oscillation phenomenon and its oscillation periods: (a) Droplet oscillation; (b) comparison of the experimental and theoretical oscillation periods.
图 4 液滴包膜的剥落与射泡现象
Figure 4. Shell peeling and bubble shooting.
图 5 厚气垫层复合液滴的形成
Figure 5. Formation of compound droplet with thick air cushion.
图 6 液滴与液膜融合穿越现象
Figure 6. Penetration by instant coalescence of droplet with film.
图 7 不同We数下液滴穿越模式分布图
Figure 7. Distribution of passing modes under various Weber numbers.
图 8 液滴前锋的绝对位移与无量纲位移特性曲线(虚线为液膜液滴的分离时刻与分离高度) (a)绝对位移; (b)无量纲位移
Figure 8. Absolute and dimensionless displacements of the droplet front, the dashed line shows the departure height and time of the droplet and film: (a) Absolute displacement curves; (b) dimensionless displacement curves.
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[1] Bartolo D, Jossereand C, Bonn D 2006 Phys. Rev. Lett. 96 124501
Google Scholar
[2] Xu W, Leeladhar R, Kang Y T, Choi C H 2013 Langmuir 29 6032
[3] Pan K L, Hung C Y 2010 Colloid Interface Sci. 352 186
[4] Thoraval M J, Takehara K, Etoh T G, Thoroddsen S 2013 J. Fluid Mech. 724 234
[5] Hu H B, Huang S H, Chen L B 2013 Chin. Phys. B 22 84702
Google Scholar
[6] Pearson T, Maynes D, Webb B W 2012 Exp. Fluids 53 603
[7] Aziz D S, Chandra S 2000 Int. J. Heat Mass Tran. 43 2841
[8] Tran T, de Maleprade H, Sun C, Lohse D 2013 J. Fluid Mech. 726 R3
Google Scholar
[9] Josserand C, Zaleski S 2003 Phys. Fluids 15 1650
Google Scholar
[10] Eggers J, Fontelos M A, Josserand C, Zaleski S 2010 Phys. Fluids 22 062101
Google Scholar
[11] Kim I, Wu X L 2010 Phys. Rev. E 82 026313
Google Scholar
[12] Yarin A L 2006 Annu. Rev. Fluid Mech. 38 159
[13] Fell D, Sokuler M, Lembach A, Eibach T F, Liu C J, Bonaccurso E, Auernhammer G K, Butt H J 2013 Colloid Polym. Sci. 291 1963
Google Scholar
[14] Gilet T, Bush J W M 2009 J. Fluid Mech. 625 167
Google Scholar
[15] Courbin L, Stone H A 2006 Phys. Fluids 18 91105
Google Scholar
[16] Bai L, Xu W, Wu P F, Lin W J, Li C, Xu D L 2016 Colloids Surf. A 509 334
Google Scholar
[17] Kim P G, Stone H A 2008 Europhys. Lett. 83 54001
Google Scholar
[18] Dorbolo S, Caps H, Vandewalle N 2003 New J. Phys. 5 161
Google Scholar
[19] Dorbolo S, Reyssat E, Vandewalle N 2005 Europhys. Lett. 69 966
Google Scholar
[20] Thoroddsen S T, Takehara K, Etoh T G 2005 J. Fluid Mech. 530 295
Google Scholar
[21] Hicks P D, Purvis R 2011 Phys. Fluids 23 062104
Google Scholar
[22] Tang X Y, Saha A, Law C K, Sun C 2019 Phys. Fluids 31 013304
Google Scholar
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