Numerical study of the evolution of bubbles during nucleation and droplets during condensation on a surface of variable wettability using the pseudopotential MRT-LBM method

Abstract

In this study, the behavior of bubbles and droplets during boiling and condensation processes on a wettable horizontal plate with variable density (${\rho }_w$) is investigated using pseudopotential lattice Boltzmann model for multiphase flow. The analysis focuses on the complete life cycle of bubbles and droplets, from their appearance to their disappearance under the effect of gravity. The main objectives of this study are to analyze the propagation of bubbles or droplets on the horizontal surface (l*) and to study their evolution as a function of time, characterized by h*, for different values of the wetting surface density. To ensure the reliability of our model in simulating these phenomena, the hydrodynamic effect and Laplace’s law were. This combination of approaches demonstrated a good compromise between our results and the references, confirming the model’s reliability. Furthermore, we present results that showcase the density behaviors for different wetting surfaces, allowing us to analyze droplet behavior on the horizontal plate. It was observed that for large values of ${\rho }_w,$ significant droplet spreading occurred, and this process took time to subside. Conversely, for small values of ${\rho }_w,$ spreading was minimal, enabling rapid droplet detachment. Interestingly, in the case of boiling, the observed behaviors were reversed compared to condensation. Moreover, the heat flux analysis for the single-density case provided insights into the temperature behavior around bubbles during the nucleation process and droplets during the droplet condensation process, while maintaining a fixed density value on average. These findings contribute to a better understanding of the thermal dynamics associated with boiling and condensation phenomena.

Keywords:

• Boiling
• condensation
• fluid flow
• lattice Boltzmann method
• phase change
• thermal exchange