Numerical Investigations of Collision Modes of Double Droplets on a Spherical Surface Based on the Phase Field Method

Droplet collision on surface is widely existed in nature and industrial production. In our research, two-dimensional rotational models and three-dimensional symmetric models based on the phase field method have been developed to simulate the collisions of continuous droplets on spherical surfaces. Using parametric dimensionless, the spreading diameter of the coalescing droplets, the width of the liquid bridge between the droplets, and the moving velocity of the three-phase contact line are obtained. When the two droplets are coaxial, the collision velocity of the droplets increases, and the radial velocity of the liquid bridge also increases. Due to the increase of droplet energy, both the first and second maximum spreading are increased, but the characteristic spreading t_s time is reduced. When using the modified capillary inertia time \(\tau_{i}^{\prime }\) ${\tau }_i^{\prime }$ normalized spreading time t_s, it is found that it fits well with the Weber number (We) by the curve 1.505 We^−0.478. Increasing the ratio of curved surface to droplet diameter λ can reduce maximum spreading time and maximum rebound height of droplet. When there is a deviation between the centers of the droplets, the spread of the droplets no longer shows symmetry and the center of the condensed droplets moves towards the offset side of the tail droplets. These findings will provide insight into the dynamics of continuous droplet collisions.