Bouncing behavior of a water droplet on a super-hydrophobic surface near freezing temperatures

A Modified Weber Number Capturing the Bouncing–Wetting Transition of Droplet Impact on Rough Surfaces

“…Impact dynamics of liquid droplet is of high significance to a variety of technological and scientific fields, such as spray bouncing-wetting transition is of particular importance to understand the liquid impact dynamics on rough hydrophobic surface. This transition has been extensively investigated through experimental studies, especially on manufactured patterned surfaces with micro-pillars, where the equilibrium contact angle of surface, [23] droplet impact velocity, [24,25] size and spacing of the pillar, [26,27] and surface temperature [28] are found to influence the droplet impact outcomes. A generalized transition criterion based on the force balance of water hammer pressure P WH , dynamic pressure P D , and capillary pressure P C is proposed to account for the bouncing-wetting transition on micro-structured surfaces, and the liquid penetration typically occurs when wetting force (P WH and P D ) is larger than anti-wetting force (P C ).…”

Suppression of wetting transition on evaporative fakir droplets by using slippery superhydrophobic surfaces with low depinning force

“…Impact dynamics of wetting transitions on micropillar surfaces were also investigated. Liu et al 34 found that in sub-millimeter scale tapered micro/nano textures, the capillary energy stored in the penetrating liquid is converted into upward motion, causing the droplet to jump without retracting, unlike conventional droplet repulsion 35 . They attributed this to the fact that on straight micropillars the stored capillary energy is not converted to upward motion because the transition from CB state to Wenzel state is more likely to occur.…”

Freezing of impact water droplets on cold surfaces

“…Instead, many researchers focused on qualitative and quantitative experimental studies [45,131,132] and numerical simulations [133][134][135][136][137]. In addition, the room temperature droplets were usually adopted because of their similar freezing features to the supercooled ones [135,[138][139][140][141][142][143][144][145].…”

“…At the early stage to investigate the freezing of the impact droplets, the molten metal droplets were usually adopted [137,[146][147][148][149]. Until the last decade, the freezing of impact water droplets on cold surfaces attracted increasing attention [145,150]. It was stated that the spreading stage on the cold surface is independent of the freezing process, but the receding stage is significantly restrained [150] and the influence of the cold temperature is less on the surface with lower wettability [151,152].…”

“…In addition, they found better water repellency against the impacting supercooled droplets was observed for the surfaces with roughness at the same scale of the critical nucleus radii. At room temperature, the water droplet can totally rebound from the superhydrophobic surfaces, as for the cold surfaces, the rebound behavior is dependent on the surface temperature and impact velocity [141,145]. To understand the freezing characteristics of the impact water droplet on the cold surfaces, many numerical works were carried out [26,43,45,168].…”