Detailed numerical simulation of multi-scale interface-vortex interactions of liquid jet atomization in crossflow

Abstract

In this paper, a detailed numerical simulation of liquid jet atomization in crossflow is performed based on the volume of fluid method coupled with the adaptive mesh refinement technique. The multi-scale phase interface evolution and the interface-vortex interaction are reported. It is found that the momentum flux ratio, Weber number, density ratio and viscosity ratio are key variables for the empirical correlation to accurately predict the atomization characteristics. Three breakup regimes, i.e., column bag breakup, surface breakup and ligament breakup, occur due to the great mass and momentum exchanges at the interface. Specially, the Kelvin-Helmholtz instability induces axial surface waves that eventually develop into column bag breakup while the Rayleigh-Taylor instability and surface thinning can induce surface breakup. Relatively, the column bag breakup generates larger liquid structures, presenting a bimodal feature. The produced ligaments either shrink to droplets or further breakup into droplets depending on their size and shape, leading to a log-normal distribution of droplet size. The interface-vortex interaction is distinctive compared to single-phase flows. A vortex core is observed to simultaneously form, grow and dissipate within each bag during the life circle of the bag, and three types of counter-rotating vortex pair exist around the column root, bag membrane and liquid droplets. Vortical structures tend to concentrate near the interface with large deformations, possessing a strong perpendicularity between the phase interface and the vortex. This work offers fundamental basis for better understanding and organization of atomization.