Re-spreading behavior of droplet impact on superhydrophobic surfaces at low Weber numbers
Jia Luo, Fuqiang Chu, Jun Zhang, Dongsheng Wen
Abstract
Despite extensive research on droplet impact behavior on superhydrophobic surfaces at high Weber numbers, there remains limited understanding of their dynamics at low Weber numbers, particularly during the retraction stage. In this study, we investigate the dynamic characteristics of droplet impact on superhydrophobic surfaces and reveal a unique re-spreading behavior during the retraction stage at smaller Weber numbers. A critical Weber number to trigger the re-spreading is identified as 4.9. A dimensionless analysis of the impact force, characterized by the dimensionless pressure, shows that the re-spreading phenomenon is the result of the competition between the inward motion driven by inertial effect and the outward expansion caused by the capillary oscillations on the contact line, which occurs only at low Weber numbers. Such a study offers insights into the dynamic characteristics of droplet impact on superhydrophobic surfaces at low Weber numbers and is of high implications for a number of related applications, such as trickle bed reactors and defrosting/deicing.