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为探索重力瞬变引起的约束液滴自激振荡机理, 本文利用落塔装置模拟短时微重力环境并借助高速CCD记录圆形限位基片上液滴整个过程的运动情况. 自激振荡是微重力下液滴形态的重整恢复过程, 边界的限位作用使得液滴在整个运动过程接触线钉扎不变, 具体可分为两个阶段: 首先是振荡的高低点位置高度渐进上升的液滴形态变化阶段, 与重力环境渐进变化有关; 而后是平衡位置附近的阻尼衰减振荡阶段, 此时振荡的频率恒定, 振幅衰减类似孤立黏性液滴的指数衰减过程. 对于第二阶段, 在高低点等位置处存在高度不变过程, 高度起伏变化时液滴振荡模式类似自由液滴二阶振荡, 高度不变时振荡模式类似自由液滴三阶振荡. 此外, 对于本实验体系的恒定接触面积的钉扎约束, 液滴的体积量不同时, 内驱振荡的阶段和模式不变, 但具体的振荡过程有所不同. 对于大体积液滴, 会在初始振荡的中间位置出现高度不变现象, 并且随振荡逐渐消失; 而小液滴中间位置则不存在此现象, 波形较一致; 第二阶段小体积液滴振幅衰减的阻尼率更大, 无量纲频率也更高.In order to further explore the oscillation mechanism of constrained droplets in microgravity and extend the application and management of space fluid, the small-amplitude self-excited oscillation processes of droplets that are pinned on a confined substrate are investigated. The substrate has a 5 mm diameter contact circle, which is implemented through the use of a drop tower and high-speed photography technology. Oscillation is a recovery procedure for droplet configuration in microgravity with the confined effect at the boundary, making the contact line and diameter unchanged throughout the entire process. A self-excited oscillation could be divided into two stages: a morphological change process and a small-amplitude damping attenuation oscillation. The first stage is a morphological change process, where the heights of high and low oscillations rise gradually, which in turn correspond to the variation of gravity. And the deformation rate is inversely proportional to the droplet size. The second stage is the small-amplitude damping attenuation oscillation around the equilibrium position until it reaches the final steady state in microgravity. At this stage, the frequency is nearly constant and the attenuation of amplitude represents an exponential damping, like the free oscillation of isolated viscous droplets. The pinning contact line makes the oscillation waveform deviate from sine curve and in the process there exists a period when the heights keep constant at some positions, such as the highest, lowest and others. Studies confirm the hypothesis that the oscillation occurs with the similar second-order mode of free drop when the height fluctuates, and the third-order mode when the height is immobile. This is in agreement with the spectral analysis. Furthermore, when the liquid volume varies within this experimental system, the pinning constraint with fixed contact area on the confined substrate can generate droplets with various static contact angles and undisturbed radii. The deformation stage and oscillation mode of the droplets remains stable, although the concrete courses differ in some ways. In the case of bigger drops, the phenomenon of height unchanging should be in the middle position and vanishes with time. However, the smaller one shows no signs for this condition, and the waveform remains consistent all around. In the second stage, the amplitude decay damping rate and non-dimensional frequency of small droplet are higher.
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Keywords:
- microgravity /
- confined substrate /
- self-excited oscillation /
- droplet volume
[1] Rayleigh J 1879 Proc. R. So. London 29 71
[2] Lamb H 1932 Hydrodynamics (London: Cambridge University)
[3] Apfel R E, Tian Y, Jankovsky J, Shi T, Chen X, Holt R G, Trinh E, Croonquist A, Thornton K C, Sacco A Jr., Coleman C, Leslie F W, Matthiesen D H 1997 Phys. Rev. Lett. 78 1912
[4] Busse F H 1984 J. Fluid Mech. 142 1
[5] Patzek T W, Basaran O A, Benner R E, Scriven L E 1995 J. Comput. Phys. 116 3
[6] Miller C A, Scriven L E 1968 J. Fluid Mech. 32 417
[7] Basaran O A, Scott T C, Byers C H 1989 AIChE J. 35 1263
[8] Tsamopoulos J A, Brown R A 1983 J. Fluid Mech. 127 519
[9] Patzek T W, Benner R E, Basaran O A, Scriven L E 1991 J. Comput. Phys. 97 489
[10] Noblin X, Buguin A, Brochard W F 2004 Eur. Phys. J. E 14 395
[11] Zhou J C, Geng X G, Lin K J, Zhang Y J, Zhang D Y 2014 Acta Phys. Sin. 63 216801(in Chinese) [周建臣, 耿兴国, 林可君, 张永建, 臧渡洋 2014 63 216801]
[12] Jiang C G, Shi L T, Zhou P, Wu C W 2011 Chin. Sci. Bull. 56 3082
[13] Mukherjee S, Johnson W L, Rhim W K 2005 Appl. Phys. Lett. 86 014104
[14] Franses E I, Basaran O A, Chang C H 1996 Curr. Opin. Colloid Interface Sci. 1 296
[15] Basaran O A, Depaoli D W 1994 Phys. Fluids 6 2923
[16] James A J, Vukasinovic B, Smith M K, Glezer A 2003 J. Fluid Mech. 476 1
[17] James A J, Vukasinovic B, Smith M K, Glezer A 2003 J. Fluid Mech. 476 29
[18] Daniel S, Chaudhury M K, De Gennes P G 2005 Langmuir 21 4240
[19] Celestini F, Kofman R 2006 Phys. Rev. E 73 041602
[20] Fujii H, Matsumoto T, Nogi K 2000 Acta Mater. 48 2933
[21] Liang R, Chen Z 2009 Microgravity Sci. Technol. 21 247
[22] Bisch C, Lasek A, Rodot H 1982 J. Mec. Theor. Appl 1 165
[23] Basaran O A, DePaoli D W 1994 Phys. Fluids 6 2923
[24] Lopez C A, Hirsa A H 2008 Nat. Photon. 2 610
[25] Jonas A, Karadag Y, Tasaltin N, Kucukkara I, Kiraz A 2011 Langmuir 27 2150
[26] Rodot H, Bisch C, Lasek A 1979 Acta Astronaut. 6 1083
[27] Strani M, Sabetta F 1984 J. Fluid. Mech. 141 223
[28] Strani M, Sabetta F 1988 J. Fluid. Mech. 189 397
[29] Siekmann J, Schilling U 1989 Appl. Microgravity Technol. 2 17
[30] Olgac U, Izbassarov D 2013 Comput. Fluids 77 152
[31] Bostwick J B, Steen P H 2009 Phys. Fluids 21 032108
[32] Theisen E A, Vogel M J, Lopez C A, Hirsa A H, Steen P H 2007 J. Fluid Mech. 580 495
[33] Ramalingam S, Ramkrishna D, Basaran O A 2012 Phys. Fluids 24 082102
[34] Zhu Z Q, Wang Y, Liu Q S, Xie J C 2012 Microgravity Sci. Technol. 24 181
[35] Zhu Z Q, Brutin D, Liu Q S, Wang Y, Mourembles A, Xie J C, Tadrist L 2010 Microgravity Sci. Technol. 22 339
[36] Wu S, Li W B, Shi F, Jiang S C, Lan D, Wang Y R 2015 Acta Phys. Sin. 64 96101(in Chinese) [吴赛, 李伟斌, 石峰, 蒋世春, 蓝鼎, 王育人 2015 64 96101]
[37] Zhang W B 2013 Ph. D. Dissertation (Beijing: Institute of Physics, Chinese Academy of Sciences) (in Chinese) [张文彬 2013 博士学位论文(北京: 中国科学院物理研究所)] 2150
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[1] Rayleigh J 1879 Proc. R. So. London 29 71
[2] Lamb H 1932 Hydrodynamics (London: Cambridge University)
[3] Apfel R E, Tian Y, Jankovsky J, Shi T, Chen X, Holt R G, Trinh E, Croonquist A, Thornton K C, Sacco A Jr., Coleman C, Leslie F W, Matthiesen D H 1997 Phys. Rev. Lett. 78 1912
[4] Busse F H 1984 J. Fluid Mech. 142 1
[5] Patzek T W, Basaran O A, Benner R E, Scriven L E 1995 J. Comput. Phys. 116 3
[6] Miller C A, Scriven L E 1968 J. Fluid Mech. 32 417
[7] Basaran O A, Scott T C, Byers C H 1989 AIChE J. 35 1263
[8] Tsamopoulos J A, Brown R A 1983 J. Fluid Mech. 127 519
[9] Patzek T W, Benner R E, Basaran O A, Scriven L E 1991 J. Comput. Phys. 97 489
[10] Noblin X, Buguin A, Brochard W F 2004 Eur. Phys. J. E 14 395
[11] Zhou J C, Geng X G, Lin K J, Zhang Y J, Zhang D Y 2014 Acta Phys. Sin. 63 216801(in Chinese) [周建臣, 耿兴国, 林可君, 张永建, 臧渡洋 2014 63 216801]
[12] Jiang C G, Shi L T, Zhou P, Wu C W 2011 Chin. Sci. Bull. 56 3082
[13] Mukherjee S, Johnson W L, Rhim W K 2005 Appl. Phys. Lett. 86 014104
[14] Franses E I, Basaran O A, Chang C H 1996 Curr. Opin. Colloid Interface Sci. 1 296
[15] Basaran O A, Depaoli D W 1994 Phys. Fluids 6 2923
[16] James A J, Vukasinovic B, Smith M K, Glezer A 2003 J. Fluid Mech. 476 1
[17] James A J, Vukasinovic B, Smith M K, Glezer A 2003 J. Fluid Mech. 476 29
[18] Daniel S, Chaudhury M K, De Gennes P G 2005 Langmuir 21 4240
[19] Celestini F, Kofman R 2006 Phys. Rev. E 73 041602
[20] Fujii H, Matsumoto T, Nogi K 2000 Acta Mater. 48 2933
[21] Liang R, Chen Z 2009 Microgravity Sci. Technol. 21 247
[22] Bisch C, Lasek A, Rodot H 1982 J. Mec. Theor. Appl 1 165
[23] Basaran O A, DePaoli D W 1994 Phys. Fluids 6 2923
[24] Lopez C A, Hirsa A H 2008 Nat. Photon. 2 610
[25] Jonas A, Karadag Y, Tasaltin N, Kucukkara I, Kiraz A 2011 Langmuir 27 2150
[26] Rodot H, Bisch C, Lasek A 1979 Acta Astronaut. 6 1083
[27] Strani M, Sabetta F 1984 J. Fluid. Mech. 141 223
[28] Strani M, Sabetta F 1988 J. Fluid. Mech. 189 397
[29] Siekmann J, Schilling U 1989 Appl. Microgravity Technol. 2 17
[30] Olgac U, Izbassarov D 2013 Comput. Fluids 77 152
[31] Bostwick J B, Steen P H 2009 Phys. Fluids 21 032108
[32] Theisen E A, Vogel M J, Lopez C A, Hirsa A H, Steen P H 2007 J. Fluid Mech. 580 495
[33] Ramalingam S, Ramkrishna D, Basaran O A 2012 Phys. Fluids 24 082102
[34] Zhu Z Q, Wang Y, Liu Q S, Xie J C 2012 Microgravity Sci. Technol. 24 181
[35] Zhu Z Q, Brutin D, Liu Q S, Wang Y, Mourembles A, Xie J C, Tadrist L 2010 Microgravity Sci. Technol. 22 339
[36] Wu S, Li W B, Shi F, Jiang S C, Lan D, Wang Y R 2015 Acta Phys. Sin. 64 96101(in Chinese) [吴赛, 李伟斌, 石峰, 蒋世春, 蓝鼎, 王育人 2015 64 96101]
[37] Zhang W B 2013 Ph. D. Dissertation (Beijing: Institute of Physics, Chinese Academy of Sciences) (in Chinese) [张文彬 2013 博士学位论文(北京: 中国科学院物理研究所)] 2150
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