The hydrodynamics and mixing during the nonaxisymmetry impingement of a micro-droplet and a sessile droplet of the same fluid are investigated by many-body dissipative particle dynamics (MDPD) simulation. In this work, the range of the impingement angle (θi) between the impinging droplet and the sessile droplet is 0° - 60° and the contact angle is set as 45° or 124°. The droplets impingement and mixing behavior is analyzed based on the droplet internal flow field, the concentration distribution and the time scale of the decay of the kinetic energy of the impinging droplet. The dimensionless total mixing time τm is calculated by a modified mixing function. With the Weber number(We) ranging from 5.65 to 22.7 and the Ohnesorge number(Oh) ranging from 0.136 to 0.214, we find τm hardly changes with We and Oh. Whereas, θi and surface wettability are found to have a significant effect on τm. We find that θi has no clear effect on τm on a hydrophobic surface, while on the hydrophilic surface, τm increase with the θi . Thus, reducing the impinging angle is a valid method to shorten the total mixing time.
- droplets impingement
- mixing behavior
- mixing time
- concentration distribution
- many-body dissipative particle dynamics