-
摘要: 以Flow-3D为基础, 对不同微织构表面上液滴的铺展过程进行了动力学仿真, 提出了三相接触线的移动机制, 并用接触线铺展标定律、铺展速度和最终铺展半径评价液滴在微织构表面上的铺展特性。试验结果表明: 液滴在微织构表面和光滑表面上分别满足相应的铺展标定律, 微织构增大了固-液接触面积, 液滴铺展过程获得了额外驱动力, 因而, 铺展速度和最终铺展半径都增大; 在正方形凹坑表面, 最终铺展半径由1.05mm增大到1.30mm, 而在正方形凸起表面, 最终铺展半径达到最大值1.62mm; 相比于微凹坑, 微凸起更有利于液滴的铺展, 由于微凸起的存在, 固-液间接触面积迅速增大, 液滴铺展获得了额外的驱动力, 加上微凸起之间形成的微通道, 三相接触线始终保持连续性特征; 反观微凹坑表面, 虽然固-液间的接触面积增大, 但是三相接触线钉扎在微凹坑内, 随着铺展速度逐渐降低, 液滴最终稳定在平衡位置; 液滴在长方形织构表面上的铺展过程具有各向异性, 平行于微织构方向的铺展速度大, 最终铺展半径为1.13mm, 铺展特性较好, 而垂直于微织构方向的铺展速度小, 由于三相接触线的不连续性, 最终铺展半径为0.94mm, 铺展特性较差。Abstract: The dynamics simulation of droplet spreading process on the different micro-textured surfaces was studied on the basis of Flow-3 D, and the moving mechanism of triple contact line was proposed. The spreading scaling laws of contact line, the spreading velocity and the final spreading radius were used to evaluate the spreading features of droplet on the micro-textured surfaces. Test result shows that droplet on the micro-textured and smooth surfaces meets two corresponding spreading scaling laws respectively. The contact area between solid and liquid increases because of the micro-textures. Because the excess driving force is obtained in the spreading process of droplet, both the spreading velocity and the final spreading radius increase. The final spreading radius on the micro-textured surface with square pits increases from 1.05 mm to 1.30 mm, and the maximum radius on the surface with square bulges is 1.62 mm. Micro-bulge is more beneficial to promote droplet spreading compared with micro-pit. Because of the existence of micro-bulges, the contact area between solid and liquid increases rapidly, the excess driving force is obtained in spreading process of droplet, the micro-channels between micro-bulges form, so the triple contact line keeps continuous feature all the time. While on the textured surface with micro-pits, the triple contact line is pinned in the micro-pits despite of the increase of contact area between solid and liquid, and the droplet eventually stays at the equilibrium position with the decrease of spreading velocity. Moreover, droplet spreading process has anisotropy on the surface with rectangle texture. The flow velocity parallelled to the micro-texture direction is higher, and the final spreading radius is 1.13 mm, which shows a good spreading feature. While the flow velocity vertical to the micro-texture direction is smaller, the spreading radius is 0.94 mm because of the discontinuity of triple contact line, so the spreading feature is poorer.
-
图 11 对数坐标系下铺展半径与时间曲线
Figure 11. Curves of spreading radius and time in logarithmic coordinate
-
[1] PAWLAK Z, URBANIAK W, OLOYEDE A. The relationship between friction and wettability in aqueous environment[J]. Wear, 2011, 270 (9/10): 1745-1749. [2] 杨淑燕, 郭峰, 马冲, 等. 固液润湿性对流体动压润滑薄膜的影响[J]. 摩擦学学报, 2010, 30 (2): 203-208. https://www.cnki.com.cn/Article/CJFDTOTAL-MCXX201002019.htmYANG Shu-yan, GUO Feng, MA Chong, et al. Influences of the liquid/solid wettability on thin hydrodynamic lubrication films[J]. Tribology, 2010, 30 (2): 203-208. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-MCXX201002019.htm [3] 朱海燕, 张翼, 赵怀瑞, 等. 基于边界层控制的高速列车减阻技术[J]. 交通运输工程学报, 2017, 17 (2): 64-72. doi: 10.3969/j.issn.1671-1637.2017.02.007ZHU Hai-yan, ZHANG Yi, ZHAO Huai-rui, et al. Drag reduction technology of high-speed train based on boundary layer control[J]. Journal of Traffic and Transportation Engineering, 2017, 17 (2): 64-72. (in Chinese). doi: 10.3969/j.issn.1671-1637.2017.02.007 [4] 周海超, 梁晨, 杨建, 等. 提升轮胎抗滑水性能的仿生方法[J]. 机械工程学报, 2015, 51 (8): 125-130. https://www.cnki.com.cn/Article/CJFDTOTAL-JXXB201508018.htmZHOU Hai-chao, LIANG Chen, YANG Jian, et al. Bionic method for improving tire anti-hydroplaning performance[J]. Journal of Mechanical Engineering, 2015, 51 (8): 125-130. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-JXXB201508018.htm [5] YOUNG T. An essay on the cohesion of fluids[J]. Philosophical Transactions of the Royal Society of London, 1805, 95: 65-87. doi: 10.1098/rstl.1805.0005 [6] WENZEL R N. Resistance of solid surfaces to wetting by water[J]. Industrial and Engineering Chemistry, 1936, 28 (8): 988-994. doi: 10.1021/ie50320a024 [7] CASSIE A B D, BAXTER S. Large contact angles of plant and animal surfaces[J]. Nature, 1945, 155 (3923): 21-22. doi: 10.1038/155021a0 [8] 程帅, 董云开, 张向军. 规则粗糙固体表面液体浸润性对表观接触角影响的研究[J]. 机械科学与技术, 2007, 26 (7): 822-827. doi: 10.3321/j.issn:1003-8728.2007.07.002CHENG Shuai, DONG Yun-kai, ZHANG Xiang-jun. Study of the influence of apparent contactangle on regular rough surface considering liquid wetting properties[J]. Mechanical Science and Technology for Aerospace Engineering, 2007, 26 (7): 822-827. (in Chinese). doi: 10.3321/j.issn:1003-8728.2007.07.002 [9] 杨常卫, 何枫, 郝鹏飞. 微结构疏水表面上液滴的表观接触角[J]. 中国科学: 化学, 2010, 40 (10): 1545-1549. https://www.cnki.com.cn/Article/CJFDTOTAL-JBXK201010010.htmYANG Chang-wei, HE Feng, HAO Peng-fei. The apparent contact angle on the micro-structured hydrophobic surface[J]. Scientia Sinica: Chimica, 2010, 40 (10): 1545-1549. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-JBXK201010010.htm [10] 陈晓玲, 吕田. 粗糙表面液滴表观形态研究[J]. 中国科学: 物理学力学天文学, 2009, 39 (1): 58-62. https://www.cnki.com.cn/Article/CJFDTOTAL-JGXK200901009.htmCHEN Xiao-ling, LU Tian. Study of apparent shape of the droplet on rough surface[J]. Scientia Sinica: Physics, Mechanica and Astronomica, 2009, 39 (1): 58-62. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-JGXK200901009.htm [11] BLAKE T D. The physics of moving wetting line[J]. Journal of Colloid and Interface Science, 2006, 299 (1): 1-13. doi: 10.1016/j.jcis.2006.03.051 [12] ORAN A, DAVIS S H, BANKOFF S G. Long-scale evolution of thin liquid films[J]. Reviews of Modern Physics, 1997, 69 (3): 931-980. doi: 10.1103/RevModPhys.69.931 [13] DE GENNES P G. Wetting: statics and dynamics[J]. Reviews of Modern Physics, 1985, 57 (3): 827-863. doi: 10.1103/RevModPhys.57.827 [14] LEGENDRE D, MAGLIO M. Comparison between numerical models for the simulation of moving contact lines[J]. Computer and Fluids, 2015, 113: 2-13. doi: 10.1016/j.compfluid.2014.09.018 [15] BARENBLATT G I, BERETTA E, BERTSCH M. The problem of the spreading of a liquid film along a solid surface: a new mathematical formulation[J]. Proceedings of the National Academy of Sciences of the United States of America, 1997, 94 (19): 10024-10030. doi: 10.1073/pnas.94.19.10024 [16] TANNER L. The spreading of silicone oil drops on horizontal surfaces[J]. Journal of Physics D: Applied Physics, 1979, 83 (9): 1473-1484. [17] YUAN Quan-zi, ZHAO Ya-pu. Multiscale dynamic wetting of a droplet on a lyophilic pillar-arrayed surface[J]. Journal of Fluid Mechanics, 2013, 716 (2): 171-188. [18] YUAN Quan-zi, ZHAO Ya-pu. Wetting on flexible hydrophilic pillar-arrays[J]. Scientific Reports, 2013, 3 (6), DOI: 10.1038/srep01944. [19] BONN D, EGGERS J, INDEKEU J, et al. Wetting and spreading[J]. Reviews of Modern Physics, 2009, 81 (2): 739-805. [20] PUJADO P R, HUH C, SCRIVEN L E. On the attribution of an equation of capillarity to Young and Laplace[J]. Journal of Colloid and Interface Science, 1972, 38 (3): 662-663. [21] 焦云龙, 刘小君, 逄明华, 等. 固体表面液滴铺展与润湿接触线的移动分析[J]. 物理学报, 2016, 65 (1): 016801-1-10. https://www.cnki.com.cn/Article/CJFDTOTAL-WLXB201601040.htmJIAO Yun-long, LIU Xiao-jun, PANG Ming-hua, et al. Analyses of droplet spreading and the movement of wetting line on a solid surface[J]. Acta Physica Sinica, 2016, 65 (1): 016801-1-8. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-WLXB201601040.htm [22] KIM S J, MOON M W, LEE K R, et al. Liquid spreading on superhy drophilic micropil lararrays[J]. Journal of Fluid Mechanics, 2011, 680: 477-487. [23] SHANAHAN M E R. Simple theory of"stick-slip"wetting hysteresis[J]. Langmuir, 1995, 11 (3): 1041-1043. [24] 焦云龙, 刘小君, 刘焜. 离散型织构表面液滴的铺展及其接触线的力学特性分析[J]. 力学学报, 2016, 48 (2): 353-360. https://www.cnki.com.cn/Article/CJFDTOTAL-LXXB201602011.htmJIAO Yun-long, LIU Xiao-jun, LIU Kun. Mechanical analysis of a droplet spreading on the discrete textured surfaces[J]. Chinese Journal of Theoretical and Applied Mechanics, 2016, 48 (2): 353-360. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-LXXB201602011.htm [25] 焦云龙, 刘小君, 逄明华, 等. 液滴平壁铺展过程中的滞后效应及力学机制研究[J]. 应用数学和力学, 2016, 37 (1): 14-26. https://www.cnki.com.cn/Article/CJFDTOTAL-YYSX201601003.htmJIAO Yun-long, LIU Xiao-jun, PANG Ming-hua, et al. Study of contact angle hysteresis at moving contact lines based on CFD simulation and mechanical analysis[J]. Applied Mathematics and Mechanics, 2016, 37 (1): 14-26. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-YYSX201601003.htm -
下载:
点击查看大图
图(14) / 表(1)
计量
- 文章访问数: 634
- HTML全文浏览量: 145
- PDF下载量: 670
- 被引次数: 0
