Research On Dynamic Characteristics Of Droplet Impacting On Magnesium Alloy Hydrophobic/Superhydrophobic Surface

The phenomenon of droplets impacting on a solid wall can be widely found in many fields, such as aerospace, biomedical and industrial production. Based on the fabrication of hydrophobic/superhydrophobic magnesium alloy surfaces, an experiment with high-speed camera system was carried out to study the dynamic characteristic of droplets impacting on magnesium alloy surfaces in this paper. Meanwhile, Computational Fluid Dynamic method was used to simulate the impacting process of droplet. This paper focused on the influences of surface wettability, dripping height and droplet size. The main contents are as follows:In order to change the surface wettability of magnesium alloy, the magnesium alloy was treated into regular dot matrix structure by laser manufacturing, and Self-Assembled Monolayers (SAMs) were deposited on these texturing surfaces. The experiment results indicated that the contact angle decreases with the increase of the dot spacing. It also shows that the surface deposited with FOTS shows the strongest hydrophobicity, and the contact angle of the surface is the biggest. While the surface deposited with MPS shows weakest hydrophobicity on which the contact angle is the smallest.The high-speed camera system was used to shot and record the process of droplets impacting on magnesium alloy surfaces. The influences of surface wettability, droplet dripping height and droplet size on the dynamic characteristic of droplet were studied. Experimental results show that, the contact diameter increases with the increase of surface wettability, dripping height and droplet size. The increase of surface hydrophobicity or the decrease of droplet size will increase the rebound height of droplets. While, on surfaces with different wettability, dripping height has different effects on the rebound factor.Computational Fluid Dynamics method was used to carry out the simulation of droplets impacting on hydrophobic/superhydrophobic walls. The influences of surface wettability, dripping height and droplet size were further discussed by analyzing the distributions of droplet’s internal pressure and velocity. The simulation results show that, the maximum contact diameter increases when the surface hydrophobicity decreases. The contact diameter also increases along with the increase of dripping height and droplet size.