表面弹性对含可溶性活性剂垂直液膜排液的影响
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摘要
针对含可溶性活性剂的垂直液膜排液过程,在考虑表面弹性作用的基础上,采用润滑理论建立了液膜厚度、表面速度、表面和内部活性剂浓度的演化方程组,通过数值计算分析了表面弹性和活性剂溶解度耦合作用下的液膜演化特征.结果表明:表面弹性是影响可溶性活性剂垂直液膜排液过程中必不可少的因素.排液初期,随表面弹性增加,液膜初始厚度增大,表面更趋于刚性化.随排液进行,弹性不同的液膜呈现不同的典型排液特征:当弹性较小时,液膜上部表面张力高,下部表面张力低,产生正向的马兰戈尼效应,与重力作用相抗衡.当弹性较大时,膜上部表面张力低,下部表面张力高,产生逆向的马兰戈尼效应,促使液膜排液加速,更易发生失稳.活性剂溶解度通过控制液膜表面的活性剂分子吸附量,进而影响表面弹性:当活性剂溶解度较大时,液膜厚度较小,很快发生破断;随溶解度降低,液膜稳定性增加,初始表面弹性也随之增大,并随液膜变薄逐渐接近极限膨胀弹性值.
The aim of the present paper is to investigate the gravity-driven draining process containing soluble surfactant when considering the coupling effects of surface elasticity and surfactant solubility. A nonlinear coupling evolution equation including liquid film thickness, surface velocity and surfactant concentration(both on the surface and in the bulk) is established based on the lubrication theory. Assuming that the top of liquid film is attached to the wireframe and the bottom is connected to a reservoir, the drainage evolution is simulated with the software called FreeFem. The effects of surface elasticity and solubility on liquid film draining are discussed under their coupling. The simulation results show that the surface elasticity is an indispensable factor in the process of liquid film drainage with soluble surfactant,and the surfactant solubility also has an important influence on the process. At the initial stage of liquid draining, the initial thickness of liquid film increases with increasing surface elasticity, and the surface tends to be more rigid; with the drainage proceeding, the liquid film with high and low elasticity illustrate different notable draining features: in the case of low surface elasticity, the distribution of surfactant forms a surface tension gradient from top to bottom on the film surface, leading to positive Marangoni effect that counteracts gravity. However, in the case of high elasticity, the film surface presents a surface tension gradient from bottom to top, resulting in a reverse Marangoni effect, which accelerates the draining and makes the film more susceptible to instability. The solubility of surfactant dominates the number of adsorbent molecules on the film surface, which affects the surface elasticity. When the solubility of the surfactant is great(β → 0), the film is extremely unstable, and it breaks down quickly. As the solubility decreases(namely, β increases),the stability of the film increases, and the initial surface elasticity also rises. The surface elasticity gradually approaches to the limiting dilational elasticity modulus due to the film being thinner.
The aim of the present paper is to investigate the gravity-driven draining process containing soluble surfactant when considering the coupling effects of surface elasticity and surfactant solubility. A nonlinear coupling evolution equation including liquid film thickness, surface velocity and surfactant concentration(both on the surface and in the bulk) is established based on the lubrication theory. Assuming that the top of liquid film is attached to the wireframe and the bottom is connected to a reservoir, the drainage evolution is simulated with the software called FreeFem. The effects of surface elasticity and solubility on liquid film draining are discussed under their coupling. The simulation results show that the surface elasticity is an indispensable factor in the process of liquid film drainage with soluble surfactant,and the surfactant solubility also has an important influence on the process. At the initial stage of liquid draining, the initial thickness of liquid film increases with increasing surface elasticity, and the surface tends to be more rigid; with the drainage proceeding, the liquid film with high and low elasticity illustrate different notable draining features: in the case of low surface elasticity, the distribution of surfactant forms a surface tension gradient from top to bottom on the film surface, leading to positive Marangoni effect that counteracts gravity. However, in the case of high elasticity, the film surface presents a surface tension gradient from bottom to top, resulting in a reverse Marangoni effect, which accelerates the draining and makes the film more susceptible to instability. The solubility of surfactant dominates the number of adsorbent molecules on the film surface, which affects the surface elasticity. When the solubility of the surfactant is great(β → 0), the film is extremely unstable, and it breaks down quickly. As the solubility decreases(namely, β increases),the stability of the film increases, and the initial surface elasticity also rises. The surface elasticity gradually approaches to the limiting dilational elasticity modulus due to the film being thinner.
引文
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[28]Champougny L,Scheid B,Restagno F,Vermant J,Rio E 2015 Soft Matter 11 2758
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[30]Jensen O E,Grotberg J B 1993 Phys.Fluids A 5 58
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[32]Afsarsiddiqui A B,And P F L,Matar O K 2003 Langmuir 19 703
[33]Ruschak K J 2010 Aiche J.33 801
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[35]Angarska J K,Ivanova D S,Manev E D 2015 Colloids Surf.A 481 87
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[37]Xiong Y,Chen D J,Wang J,Zhang Q,Wu W G,Yao Y 2008 J.Oil Gas Techn.30 136(in Chinese)[熊颖,陈大钧,王君,张谦,吴文刚,尧艳2008石油天然气学报30136]
[38]Kumar N,Couzis A,Maldarelli C 2003 J.Colloid Interface Sci.267 272
[39]Hsu C,Chang C,Lin S 1999 Langmuir 15 1952
[40]Berg S,Adelizzi E A,Troian S M 2005 Langmuir 213867
[41]Karakashev S I,Nguyen A V 2007 Colloids Surf.A 293229
[2]Lee K S,Ivanova N,Starov V M,Hilal N,Dutschk V2008 Adv.Colloid Interface Sci.144 54
[3]Afsar-Siddiqui A B,Luckham P F,Matar O K 2003 Adv.Colloid Interface Sci.106 183
[4]Xe J N 2007 Int.Med.Health Guid.News 13 44(in Chinese)[谢绛凝2007国际医药卫生导报13 44]
[5]Couder Y,Chomaz J M,Rabaud M 1989 Physica D 37384
[6]Langevin D 2014 Annu.Rev.Fluid Mech.46 47
[7]Lucassen-Reynders E H,Cagna A,Lucassen J 2001 Colloids Surf.A 186 63
[8]Mysels K J,Shinoda K,Frankel S 1959 Soap Films:Studies of Their Thinning and a Bibilography(New York:Pergammon)p116
[9]Naire S,Braun R J,Snow S A 2001 Phys.Fluids 132492
[10]Ye X M,Yang S D,Li C X 2017 Acta Phys.Sin.66184702(in Chinese)[叶学民,杨少东,李春曦2017物理学报66 184702]
[11]Schwartz L W,Roy R V 1999 J.Colloid Interface Sci.218 309
[12]Seiwert J,Benjamin D,Isabelle C 2014 J.Fluid Mech.739 124
[13]Ye X M,Yang S D,Li C X 2017 Acta Phys.Sin.66194701(in Chinese)[叶学民,杨少东,李春曦2017物理学报66 194701]
[14]Ye X M,Li M L,Zhang X S,Li C X 2018 Acta Phys.Sin.67 164701(in Chinese)[叶学民,李明兰,张湘珊,李春曦2018物理学报67 164701]
[15]Yiantsios S G,Higgins B G 2010 Phys.Fluids 22 022102
[16]Lin C K,Hwang C C,Uen W Y 2000 J.Colloid Interface Sci.231 379
[17]Shi D,Gu H X,Liu X Y,Fan Q L 2004 China Surf.Deterg.Cosmet.34 229(in Chinese)[史东,谷惠先,刘晓英,樊全莲2004日用化学工业34 229]
[18]Luo J,Gao B J,Wang J F,Cao Y,Yuan H 2000 Acta Polym.Sin.1 262(in Chinese)[罗娟,高保娇,王久芬,曹远,袁宏2000高分子学报1 262]
[19]Bergeron V 1997 Langmuir 13 3474
[20]Monroy F,Kahn J G,Langevin D 1998 Colloids Surf.A 143 251
[21]Lucassen J,Tempel M V D 1972 Chem.Eng.Sci.271283
[22]Santini E,Ravera F,Ferrari M,Stubenrauch C,Makievski A,Kr?gel J 2007 Colloids Surf.A 298 12
[23]Beneventi D,Pugh R J,CarréB,Gandini A 2003 J.Colloid Interface Sci.268 221
[24]Georgieva D,Cagna A,Langevin D 2009 Soft Matter 52063
[25]Wang L,Yoon R H 2008 Int.J.Miner.Process.85 101
[26]Wang L,Yoon R H 2006 Colloids Surf.A 282 84
[27]Karakashev S I,Ivanova D S 2010 J.Colloid Interface Sci.343 584
[28]Champougny L,Scheid B,Restagno F,Vermant J,Rio E 2015 Soft Matter 11 2758
[29]Seiwert J,Cantat I 2015 Colloids Surf.A 473 2
[30]Jensen O E,Grotberg J B 1993 Phys.Fluids A 5 58
[31]Zhao Y P 2012 Physical Mechanics of Surface and Interface(Beijing:Science Press)pp185,186(in Chinese)[赵亚溥2012表面与界面物理力学(北京:科学出版社)第185,186页]
[32]Afsarsiddiqui A B,And P F L,Matar O K 2003 Langmuir 19 703
[33]Ruschak K J 2010 Aiche J.33 801
[34]Saulnier L,Restagno F,Delacotte J,Langevin D,Rio E2011 Langmuir 27 13406
[35]Angarska J K,Ivanova D S,Manev E D 2015 Colloids Surf.A 481 87
[36]Xiong Z 2012 Farm Prod.Process.3 67(in Chinese)[熊拯2012农产品加工3 67]
[37]Xiong Y,Chen D J,Wang J,Zhang Q,Wu W G,Yao Y 2008 J.Oil Gas Techn.30 136(in Chinese)[熊颖,陈大钧,王君,张谦,吴文刚,尧艳2008石油天然气学报30136]
[38]Kumar N,Couzis A,Maldarelli C 2003 J.Colloid Interface Sci.267 272
[39]Hsu C,Chang C,Lin S 1999 Langmuir 15 1952
[40]Berg S,Adelizzi E A,Troian S M 2005 Langmuir 213867
[41]Karakashev S I,Nguyen A V 2007 Colloids Surf.A 293229