Coalescence-induced jumping of immersed and suspended droplets onmicrostructured substrates
DOI:
https://doi.org/10.13052/17797179.2017.1306830Keywords:
Lattice Boltzmann method, droplet coalescence, structured superhydrophobic substrate, self-propelled jumping, Wenzel–Cassie wettingAbstract
The coalescence-induced jumping of liquid droplets on superhydrophobic structured substrates is investigated numerically using a three-dimensional multiphase lattice Boltzmann method. The numerical experiments on evolution of droplets during jumping process show higher jumping velocity and height from superhydrophobic substrates structured with a periodic array of square pillars, than flat superhydrophobic substrateswith an equilibrium contact angle of 180◦. The results further reveal a strong effect of pillars on the vertical jumping velocity and the final quasiequilibrium height of the merged droplet as a function of air and liquid viscosity, as well as air inertia. As for substrate wettability, it is found that, compared to the flat superhydrophobic substrate, the critical contact angle where the merged droplet jumps away from substrate is reduced for pillared substrate and is about 120◦. It is also observed that the droplet initial placement on a substrate with a square array of pillars has an important effect on the spontaneous jumping of the coalesced droplet, and a Wenzel–Cassie wetting transition upon coalescence is observed for droplets that are initially immersed within the pillars.
Downloads
References
Boreyko, J. B., & Chen, C. H. (2009). Self-propelled dropwise condensate on
super-hydrophobic surfaces. Physics Review Letters, 103, 184501. doi:10.1103/Phys-
RevLett.103.184501
Cahn, J. W. (1977). Critical-point wetting. The Journal of Chemical Physics, 66, 3667–3672.
doi:10.1063/1.434402
Chen, C. H., Cai, C. L., Tsai, C. L., Chen, C. L., Xiong, G., Yu, Y., & Ren, Z. (2007).
Dropwise condensation on superhydrophobic surfaces with two tier roughness. Applied
Physics Letters, 90, 173108. doi:10.1063/1.2731434
Chen, X. M., Wu, J., Ma, R. Y., Hua, M., Koratkar, N., Yao, S. H., & Wang, Z. K.
(2011). Nanograssed micropyramidal architectures for continuous dropwise condensation.
Advanced Functional Materials, 21, 4617–4623. doi:10.1002/adfm.201101302
Chen, X., Patel, R. S.,Weibel, J. A.,&Garimella, S.V. (2016). Coalescence-induced jumping of
multiple condensate droplets on hierarchical superhydrophobic surfaces. Scientific Reports,
, 18649. doi:10.1038/srep18649
Farokhirad, S.,Morris, J. F.,&Lee, T. (2015). Coalescence-induced jumping of droplet: Inertia
and viscosity effects. Physics of Fluids, 27, 102102. doi:10.1063/1.4932085
Feng, J., Qin, Z. Q., & Yao, S. H. (2012). Factors affecting the spontaneous motion
of condensate drops on superhydrophobic copper surfaces. Langmuir, 28, 6067–6075.
doi:10.1021/la300609f
Forsberg, P., Nikolajeff, F., & Karlsson, M. (2011). Cassie-Wenzel and Wenzel-Cassie
transitions on immersed superhydrophobic surfaces under hydrostatic pressure. Soft
Matter, 7, 104–109. doi:10.1039/C0SM00595A
Kim, A., Lee, C., Kim, H., & Kim, J. (2015). Simple approach to superhydrophobic
nanostructured Al for practical anti-frosting application based on enhanced selfpropelled
jumping droplets. ACS Applied Materials and Interfaces, 7, 7206–7213.
doi:10.1021/acsami.5b00292
Lee, T. (2009). Effects of incompressibility on the elimination of parasitic currents in the
lattice Boltzmann equation method for binary fluids. Computers and Mathematics with
Applications, 58, 987–994. doi:10.1016/j.camwa.2009.02.017
Lee, T., & Liu, L. (2010). Lattice Boltzmann simulations of micron-scale drop impact on dry
surfaces. Journal of Computational Physics, 229, 8045–8063. doi:10.1016/j.jcp.2010.07.007
Liu, F., Ghigliotti,G., Feng, J. J.,&Chen, C. H. (2014). Numerical simulations of self-propelled
jumping upon drop coalescence on non-wetting surfaces. Journal of Fluid Mechanics, 752,
–65. doi:10.1017/jfm.2014.320
Liu, L.&Lee, T. (2009). Wall free energy based polynomial boundary conditions for non-ideal
gas lattice Boltzmann equation. International Journal of Modern Physics, 20, 1749–1768.
doi:10.1142/S0129183109014710
Liu, T. Q., Sun, W., Sun, X. Y., & Ai, H. R. (2012). Mechanism study of condensed
drops jumping on super-hydrophobic surfaces. Colloids and Surfaces A, 414, 366–374.
doi:10.1016/j.colsurfa.2012.08.063
Liu, X., & Cheng, P. (2015). 3D multiphase lattice Boltzmann simulations for
morphological effects on self-propelled jumping of droplets on textured superhydrophobic
surfaces. International Communications in Heat and Mass Transfer, 64, 7–13.
doi:10.1016/j.icheatmasstransfer.2015.03.002
Miljkovic, N., Enright, R., Nam, Y., Lopez, K., Dou, N., Sack, J., & Wang, E. N. (2013).
Jumping-droplet-enhanced condensation on scalable super-hydrophobic nanostructured
surfaces. Nano Letters, 13, 179–187. doi:10.1021/nl303835d
Miljkovic, N., Enright, R., & Wang, E. N. (2012). Effect of droplet morphology on growth
dynamics and heat transfer during condensation on superhydrophobic nanostructured
surfaces. NANO, 6, 1776–1785. doi:10.1021/nn205052a
Miljkovic, N., Enright, R., & Wang, E. N. (2013). Modeling and optimization of superhydrophobic
condensation. Journal of Heat Transfer, 135, 111004. doi:10.1115/1.4024597
Nam, Y., Kim, H., & Shin, S. (2013). Energy and hydrodynamic analysis of coalescenceinduced
jumping droplets. Applied Physics Letters, 103, 161601. doi:10.1063/1.4825273
Peng, B., Wang, S., Lan, Z., Xu, W., Wen, R., & Ma, X. (2013). Analysis of droplet jumping
phenomenon with lattice Boltzmann simulation of droplet coalescence. Applied Physics
Letters, 102, 151601. doi:10.1063/1.4799650
Shi, Y., Tang, G., & Xia, H. (2015). Investigation of coalescence-induced droplet
jumping on superhydrophobic surfaces and liquid condensate adhesion on slit
and plain fins. International Journal of Heat and Mass Transfer, 88, 445–455.
doi:10.1016/j.ijheatmasstransfer.2015.04.085
Wang, F. C., Yang, F., & Zhao, Y. P. (2011). Size effect on the coalescence-induced selfpropelled
droplet. Applied Physics Letters, 98, 053112. doi:10.1063/1.3553782
Wenzel, R. N. (1936). Resistance of solid surfaces to wetting by water. Industrial and
Engineering Chemistry Research, 28, 988–994. doi:10.1021/ie50320a024
Wisdom, K. M., Watson, J. A., Liu, F., Watson, G. S., & Chen, C. H. (2013). Selfcleaning
of super-hydrophobic surfaces by self-propelled jumping condensate. Proceedings
of the National Academy of Sciences of the United States of America., 110, 7992–7997.
doi:10.1073/pnas.1210770110
Zhang, R., Farokhirad, S., Lee, T., & Koplik, J. (2014). Multiscale liquid drop impact on
wettable and textured surfaces. Physics of Fluids, 26, 082003. doi:10.1063/1.4892083
