Lattice Boltzmann modeling of primary liquid film breakup at the prefilmer edge: Effects of surface wettability

In this paper, numerical predictions are performed for a planar prefilming atomizer using the lattice Boltzmann (LB) method. The main target is to inspect the effects of surface wettability on the primary liquid film breakup at the prefilmer edge. To this end, a phase-field-based multiple-relaxation-time LB model for two-phase flow is derived and verified for the present study, as well as the wetting boundary scheme. After that, the effects of surface wettability are assessed by specifying different contact angles during the simulations. Numerical results indicate that the whole primary breakup process of the liquid film can be roughly divided into three interactive stages: (i) liquid accumulation at the trailing edge; (ii) ligament formation and its flapping movements; (iii) ligament breakup and droplet formation. It is visible that the liquid accumulation and the following ligament breakup show similar periodic patterns with quite consistent frequencies. Besides, when the contact angle is increased, the volume of liquid accumulated at the prefilmer edge declines, the maximum flapping region of ligaments shrinks, the ligament breakup length reduces, but the ligament breakup frequency increases. Based on the above-mentioned results, it can be concluded that the prefilmer with hydrophobic surfaces benefits the primary liquid film breakup in the close vicinity of the prefilmer edge.