Lattice Boltzmann Simulation of Drop Collision and Surface Impingement at High Density Ratio

Abstract

In this work, a novel two-phase lattice Boltzmann method (LBM) has been employed to study droplet impact dynamics in the presence of a surrounding lighter phase. All the simulations are conducted in a three-dimensional Cartesian coordinate system, and the density ratio of the liquid phase to the gas phase is fixed at 50. First, simulations of binary droplet collisions are conducted to validate the methodology for 20<We<80. Three different types of outcome, namely coalescence collision, separating collision and stretching collision, are presented. Secondly, the normal impact of a liquid drop impinging on a perfectly smooth dry surface is simulated at various liquid Weber and Reynolds numbers. Results are shown in order to compare the spread factor dependence on impact velocity, liquid density, liquid viscosity, surface tension and surface wetting characteristics. The results are validated with experimental data. Two different outcomes are obtained: deposition and splashing break-up. The transition to splashing is found to be dependent on the liquid Weber and Reynolds numbers. Nomenclature a,b,T = free parameter determining φ B = impact parameter ei = particle velocity D = diameter of the droplet d = diameter of the liquid lamella Ei, Fi, Hi = coefficients in equilibrium distribution functions i f = particle distribution function for an order parameter eq i f = equilibrium particle distribution function for i f i g = particle distribution function for predicted velocity u * eq i