Numerical Investigation of Off-center Collision between Two Equal-sized Water Droplets

Droplet collision is a basic phenomenon in numerous natural and industrial processes, while the understanding of collision dynamics is still lacking. In this work, a numerical investigation of off-center collision of two equal-sized water droplets is performed with the Weber number of 14 to 196 and impact parameter of 0 to 0.8. The incompressible Navier-Stokes equations are solved by the finite volume method. Volume of Fluid (VOF) method and adaptive mesh technique are used to capture the gas-liquid interface. Firstly, by comparing with reliable published experimental data, the reliability of the numerical results is verified. Then the shape evolution for coalescence, reflexive separation and stretching separation is described detailly. The effect of the Weber number and impact parameter on the collision of two equal-sized water droplets is analyzed. Moreover, the analysis of the surface energy and kinetic energy is conducted for the collision process. Furthermore, the dimensions of ligament and bridge for high impact parameter stretching separation are presented quantitatively. Finally, the collision outcome for the simulation cases in this work is depicted and discussed. This study is helpful for fundamentally understanding the mechanism of collision dynamics of droplets, as well as applying droplet collision model to related processes.