Droplet Upward Movement on an Inclined Surface Under Wetting Gradient: Lattice Boltzmann Simulation

doi:10.19596/j.cnki.1001-246x.8325

Abstract

Abstract:

A lattice Boltzmann method based on Shan-Chen pseudo-potential model was used to simulate the process of a droplet overcoming gravity and moving upward on a inclined plane with wetting gradient. Effects of wetting gradient, droplet size, Bond number and surface inclination angle on droplet motion were investigated. It shows that velocity vector appears in the droplet moving upwards along the slope. The greater the wetting gradient is, the faster the droplet moves, and the longer the wetting length is, and the faster the dynamic contact angle decreases. Droplet size and Bond number have weak influence on droplet motion, but there is a critical Bond number, beyond which the droplet moves down along the gradient wetting surface. The surface inclination angle has a significant effect on the droplet motion. As the inclination angle increases, the droplet motion speed and wetting length are significantly reduced.

Key words: lattice Boltzmann method, wetting gradient, droplet, Bond number, inclination angle

CLC Number:

O359

Lu CHEN, Ming GAO, Jia LIANG, Dongmin WANG, Yugang ZHAO, Lixin ZHANG. Droplet Upward Movement on an Inclined Surface Under Wetting Gradient: Lattice Boltzmann Simulation[J]. Chinese Journal of Computational Physics, 2021, 38(6): 672-682.

Figures/Tables 14

Fig.1 Physical model

Fig.2 D2Q9 model

Fig.3 Verification of Young-Laplace law

Fig.4 Relation between interaction strength and contact angle

Fig.5 Schematic of a droplet in a horizontal wetting gradient movement

Fig.6 Comparison of simulation result and theoretical prediction

Fig.7 Morphological change of a droplet moving upward on a surface with different inclined wetting gradients

Fig.8 Velocity field of droplet movement under different wetting gradients

Fig.9 (a) Variation of droplet velocity with position and (b) variation of wetting length with time under different wetting gradients

Fig.10 Variation of (a) dynamic advancing contact angle and (b) receding contact angle and (c) their difference with position

Fig.11 (a) Velocity of droplet with different size changes with position and (b) wetting length changes with time

Fig.12 (a) Variation of droplet velocity with position and (b) variation of wetting length with time at different Bond numbers (r=15, 19.3°/14 lu)

Fig.13 Relation between critical Bond number and wetting gradient

Fig.14 (a) Variation of droplet velocity with position and (b) variation of wetting length with time at different tilt angles

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