Influence of the wettability on the liquid breakup in planar prefilming airblast atomization using a coupled lattice Boltzmann–large eddy simulation model

Abstract

In this paper, an efficient coupled lattice Boltzmann–large eddy simulation model [X. An et al., “Coupled lattice Boltzmann-large eddy simulation model for three-dimensional multiphase flows at large density ratio and high Reynolds number,” Phys. Rev. E 104, 045305 (2021)] based on the Allen–Cahn phase-field theory is introduced for simulating the liquid breakup in planar prefilming airblast atomization. This is the first time that the lattice Boltzmann method is used in the three-dimensional numerical investigation of prefilming airblast atomization to the best of our knowledge. The present model utilizes two evolution equations: one is used to capture the fluid interface, and another is adopted to solve hydrodynamic properties. An advanced multiple-relaxation-time scheme is also applied for the collision operator to enhance the numerical stability. To investigate the influence of the wettability on the liquid breakup accurately, a simple and efficient wetting boundary scheme is delicately designed and strictly validated. Additionally, to evaluate the atomization quality intuitively, an atomization efficiency coefficient is proposed for characterizing the liquid breakup process. The numerical results reveal that the influence of the wettability lies in the liquid accumulation phenomenon at the edge of the prefilmer and the droplet movement in the vertical direction. The atomization quality adopting a non-wetting prefilmer is better than other cases, according to the atomization efficiency coefficients, the mean droplet equivalent diameters with their size distribution proportions, and the atomization angles in the vertical direction. In addition, it is also found that the droplet proportion above the prefilmer increases as the contact angle increases, and the proportions on both sides of the prefilmer account for 50% at the contact angle of 90°.