Simulation of double droplets impact on liquid film by a simplified lattice Boltzmann model

Abstract

A simplified method is proposed to reduce the calculated quantity of two-phase lattice Boltzmann (LB) model for large density ratio. The simplified model not only apparently reduces the calculated quantity but also has a good stability for two-phase flow with large density ratio. Based on the simplified two-phase LB model, the impingement of droplet onto a stationary liquid film is simulated. The simulation of single droplet impacts onto liquid film is used to verify the applicability of the simplified model for the impingement process. It shows that the results calculated by the simplified model are in good agreement with experimental data in published paper. Then, the impingement process of double droplets with a horizontal distance and time interval onto a liquid film is simulated by two-phase lattice Boltzmann model. Different horizontal distances, droplet diameters, impact velocities, Reynolds numbers, relative film thicknesses and time intervals between the droplets are considered. The mechanism of the impingement process is analyzed. The rule of middle splash height is obtained. The changing rule of the middle splash height and the horizontal distance has a relationship with the droplet diameter. Larger Reynolds number makes height rise faster. Thicker liquid film leads a higher height but a slower rising rate. The time interval between the droplets would destroy the symmetry and make the flow become complex. It changes the middle splash direction and lowers the splash height. The flow mechanism of the impingement process is elaborated.