Dynamic Characteristics Of Droplet Impaction On Superhydrophobic Surface Of Submillimeter Textured Column

The phenomenon of droplet impingement on solid superhydrophobic wall surface is common and widely exists in production and life,such as anti-corrosion,anti-ice deicing and wall self-cleaning and so on.The dynamic behavior and contact time of liquid droplet on superhydrophobic wall directly affect its practical application effect.Therefore,it is of great practical significance to master the dynamic behavior characteristics and contact time of liquid droplet impact on solid superhydrophobic wall.The dynamic behaviors of droplet impinging on solid wall,such as complete rebound,fracture rebound,fragmentation,crown sputtering and deposition,are mainly affected by the structural characteristics of solid wall,wall wettability,droplet impinging Angle,droplet Weber number and physical properties of droplet,such as density,viscosity and surface tension.At present,the research on changing the dynamic characteristics and contact time of droplets by changing the structural characteristics of solid walls is in the initial stage,so it is necessary to further study the influence mechanism of wall structure on droplet dynamics and contact time,so as to explore better superhydrophobic wall structure to reduce the contact time of droplets.In this paper,the dynamic characteristics of droplets on the superhydrophobic surface of textured square column,ridge and textured ring column were investigated.The purpose of this paper is to reveal the droplet impact on the superhydrophobic surface of submillimeter structure,the droplet dynamic characteristics and contact time variation law,and to provide a theoretical basis for efficient anti-icing and dust,deicing and dust removal and anti-corrosion.The results show that droplet impact on superhydrophobic surface of different structures presents different dynamic processes and contact time.Droplet impact on superhydrophobic surface of submillimeter textured square column and ridge structure has asymmetric spreading,while droplet impact on superhydrophobic surface of submillimeter textured ring column structure has symmetrical spreading.Compared with symmetric shrinkage,the contact time can be reduced significantly.Meanwhile,the grain spacing can effectively inhibit droplet spreading and increase the icing barrier to inhibit icing.The spread asymmetry is enhanced with the increase of the distance between the square column structures,but the contact time is not shorter with the stronger the asymmetry,and the contact time of droplets is minimum with the optimal submillimeter column distance.The spread,retraction and contact time characteristics of droplet impact on square column and ring column structure are similar to those of droplet impact on smooth superhydrophobic surface,which are not affected by the change of Weber number.However,the contact time of droplets on the superhydrophobic surface of the ridge structure decreased significantly with the increase of Weber number,and the contact time decreased by42.5% when the Weber number was between 8.1 and 111.11.The droplet impinges on the ridge structure and spreads asymmetrical on the superhydrophobic surface.On the ridge,the liquid film spreads thinner and enters the retraction stage faster,or the droplet breaks into two daughter droplet shrink separately.The droplet impact on the superhydrophobic surface of the ridge with different shapes showed different dynamic characteristics.Compared with the triangular ridge and the square column ridge,the semi-circular ridge could reduce the contact time between the droplet and the solid wall more effectively.Simply changing the ridge height can not reduce the contact time,but only the droplet storage of sufficient kinetic energy and reasonable ridge height can effectively reduce the contact time.The droplet impings on the superhydrophobic surface of the axisymmetric textured ring column structure and spreads symmetrically.During the phase of liquid film retraction,the dimensionless diameter changes and napping occurs.The droplet diameter has a significant influence on the non-dimensional diameter of the droplet impacting on the superhydrophobic surface of different structures and the contact time of the droplet.The larger the diameter,the larger the droplet spreading,the longer the spreading time and the longer the retraction time.