Lattice Boltzmann simulation of droplet condensation on a surface with wettability gradient

Abstract

In this paper, a free energy lattice Boltzmann model of vapor condensation on a surface with a wettability gradient is developed and numerically analyzed to understand the microscopic behaviors of self-propelled droplet condensation. The effect of wettability gradient on droplet self-motion and coalescence as well as vapor condensation is examined and investigated. The condensation rate is presented during the whole droplet condensation process to analyze the role of wettability gradient on droplet condensation. The results indicate that the surface with wettability gradient is preferred for vapor condensation owing to the appearance of self-propelled droplet condensation. Condensate film is initially spread on the high surface energy region, and liquid nucleation sites form, grow and, subsequently, coalesce with other droplets on low surface energy regions. The condensation rate is higher on a surface with a larger wettability gradient due to the more effective removal of condensate. In addition, the condensation rate fluctuates with time at the quasi-steady-state stage. During the condensation process, the droplet coalescence triggers a sudden peak of condensation rate, and the generation of new nucleation results in a rapid increase in the condensation rate.

Study on the motion characteristics of a single droplet impacting stationary wall based on the pseudopotential MRT-LBM model

“…Li et al [11][12][13][14][15][16] improved the pseudopotential force model, wall wettability model and adjustable surface tension model under large density ratio, combined with the MRT-LBM model of multi-relaxation, gas state equation, etc., and simulated and studied the multiphase ow boiling heat transfer and phase transition process. The simulation of droplet impact on stationary walls based on the lattice Boltzmann method has also been thoroughly studied, such as the study of droplets, walls, environment and other aspects [17][18][19][20][21] .…”

Nano-droplet jumping due to surface wettability variation: molecular modeling approach

“…7,19,20 In our previous study, it was shown that the behavior of a nano-droplet on a graphene surface can be influenced by the application of both constant and oscillating external electric fields. 20 Shen et al 21 considered the effect of surface wettability gradients on the dynamics of droplets, and they demonstrated droplet movement along the substrate gradient direction due to the non-uniform surface tension on the perimeter of a droplet base, which applied a directional force on the droplet. In some other studies, it was reported that the variation of wetting properties at the liquid-solid interface can provide outward forces caused by the surface energy variation, which may lead to drops spreading, partial bouncing, or complete bouncing depending on the impact conditions and surface wettability.…”

Lattice Boltzmann investigation of flow boiling in a microchannel

“…In this context, the lattice Boltzmann (LB) method has been recently emerged as a powerful method to study the fluid flow, 10,11 fluid-structure interaction, 12,13 and phase change problem. 14 In particular, the pseudo-potential multiphase LB model, that is, the Shan–Chen model imposes a short-range attraction between different phases to arise the phase segregation, thus directly capturing the phase interface in the absence of interface-tracking algorithms. 15 Besides, the nucleation sites in LB are activated by the natural evolution of the energy equation, which avoids the artificial assignment of the initial bubble nucleus.…”