Evolutionary modeling and mechanistic analysis of the impact dynamics between free-falling droplets and a sessile droplet on an anisotropic surface
Document Type
Article
Publication Date
3-5-2025
Department
Department of Manufacturing and Mechanical Engineering Technology
Abstract
The phenomenon of droplets impacting sessile droplets involves rebound and fusion between the two droplets, and is closely related to practical applications such as drug sprays and spray coatings. In this paper, the vertical lift method is utilized to realize a central collision between the two droplets, and evolutionary model of the impact dynamics is investigated by using a high-speed camera. By varying the Weber number of the falling droplets impinging on different volumes of residual droplets on a curved surface, three patterns exhibited are generalized: sphere-rebound (S-R), non-spherical-rebound (N-S-R) and extrusion-fusion (E-F). Phase diagrams are plotted to predict under what conditions satellite droplets appear. The height of the maximum stretching point (MSP) is mainly determined by the impact mode rather than the impact kinetic energy. We have also developed a mathematical model for the combined liquid's height in the E-F model, which is accurate to within 20 % for more than 80 % of the data which is a new contribution not found in previous work. Additionally, a computational model that captures the viscous dissipation of the spreading process in the S-R mode based on energy conservation has been developed. The greatest value of the viscous dissipation is shown to be less than 1.8 % of the kinetic energy of the falling droplet. Another technique, based on an “integral method”, was utilized to increase the robustness of the model based on the energy conservation principle. The results of both these methods are consistent, but differ significantly from the prior “1/2-rule” effect.
Publication Title
Colloids and Surfaces A: Physicochemical and Engineering Aspects
Recommended Citation
Tian, J.,
Wu, M.,
Mehendale, S. S.,
&
Zhang, Z.
(2025).
Evolutionary modeling and mechanistic analysis of the impact dynamics between free-falling droplets and a sessile droplet on an anisotropic surface.
Colloids and Surfaces A: Physicochemical and Engineering Aspects,
708.
http://doi.org/10.1016/j.colsurfa.2024.135948
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p2/1353