水平固体表面温度梯度下硅油液滴运动
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摘要
液滴的操控技术成为当今微流体技术的重要发展方向,气-液、气-固、固-液等界面问题日益突出。首先通过实验方法,研究了在水平固体表面液滴由温度梯度引起的热毛细迁移行为,从理论方面分析了温度梯度、接触角滞后作用对液滴迁移速度的影响。然后通过数值模拟方法求解N-S方程耦合能量方程,获得硅油液滴运动过程内部温度场和流场的变化过程。结果表明:当基底存在温度梯度时,液滴在基底表面会向冷端迁移,并伴随着接触角滞后现象,表面张力梯度作用使液滴内部产生两个涡胞,涡胞的发展影响液滴的迁移过程,两个涡胞发展为单个涡胞,液滴迁移速度趋于稳定。
The droplet control technique has become an important development direction in microfluidics technology,gas-liquid,gas-solid and solid-liquid interface effect problems have become increasingly prominent.Firstly,the experimental method was used to research the droplet thermocapillary migration induced by the temperature gradient in the horizontal solid surface.The influences of the temperature gradient and the contact angle hysteresis on the droplet migration velocity were analyzed theoretically.Then,the numerical simulation method was used to solve the N-S equation coupled the energy equation,the change processes of the internal temperature and flow fields during the silicone oil droplet motion process were obtained.The results show that when there is a temperature gradient in the substrate,the droplet will migrate to the cold end on the substrate surface with the contact angle hysteresis phenomenon.A surface tension gradient of a droplet creates two vortex cells inside the droplet,and the development of the vortex cells affects the migration of droplet.Two vortex cells gradually develop into a single vortex cell,and the droplet migration velocity tends to be stable.
The droplet control technique has become an important development direction in microfluidics technology,gas-liquid,gas-solid and solid-liquid interface effect problems have become increasingly prominent.Firstly,the experimental method was used to research the droplet thermocapillary migration induced by the temperature gradient in the horizontal solid surface.The influences of the temperature gradient and the contact angle hysteresis on the droplet migration velocity were analyzed theoretically.Then,the numerical simulation method was used to solve the N-S equation coupled the energy equation,the change processes of the internal temperature and flow fields during the silicone oil droplet motion process were obtained.The results show that when there is a temperature gradient in the substrate,the droplet will migrate to the cold end on the substrate surface with the contact angle hysteresis phenomenon.A surface tension gradient of a droplet creates two vortex cells inside the droplet,and the development of the vortex cells affects the migration of droplet.Two vortex cells gradually develop into a single vortex cell,and the droplet migration velocity tends to be stable.
引文
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[4]BRZOSKA J B,BROCHARD-WYART F,RONDELEZ F.Motions of droplets on hydrophobic model surfaces induced by thermal gradients[J].Langmuir,1993,9(8):2220-2224.
[5]CHEN J Z,TROIAN S M,DARHUBER A A,et al.Effect of contact angle hysteresis on thermocapillary droplet actuation[J].Journal of Applied Physics,2005,97(1):014906-1-014906-9.
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[9]DAGGOLU P,YECKEL A,BLEIL C E,et al.Thermal-capillary analysis of the horizontal ribbon growth of silicon crystals[J].Journal of Crystal Growth,2012,355(1):129-139.
[10]李友荣,邓努波,吴双应,等.表面张力温度系数对硅单晶生长的影响[J].材料研究学报,2005,19(4):395-400.
[11]SETHIAN J A.Level set methods and fast marching methods[J].Journal of Computing&Information Technology,1999,11(1):400.
[12]SUSSMAN M,FATEMI E.An efficient,interface-preserving level set redistancing algorithm and its application to interfacial incompressible fluid flow[J].SIAM Journal on Scientific Computing,1999,20(4):1165-1191.
[13]段俐,康琦,胡文瑞.液层厚度对浮力-热毛细对流面型的影响[J].力学学报,2004,36(6):641-648.