Dynamic Behaviors of Droplet Impact and Spreading: Water on Five Different Substrates

Abstract

The dynamic wetting behaviors, especially the droplet morphology, of a water droplet impinging on five substrate surfaces were investigated. A water drop was released from 13.6 mm above a solid surface and impinged on substrates. The images (the silhouette and 45 degrees top view) were sequentially recorded from the moment that the droplet impacted the solid surface until it reached equilibrium. The entire profile of each of the water droplets during spreading was obtained from the digitized recorded images. The digitized droplets were then used to detail the spreading mechanism, including information on the relaxations of the wetting diameter, droplet height, contact angle, and spreading velocity. A comparison of the full droplet profiles allows us to clarify the independent motion of two related but independent components, the central region and rim, of an impinging droplet. An interesting plateau region in the droplet height relaxation curve was observed in the first cycle for all substrate surfaces. For hydrophobic surfaces (paraffin and Teflon), three particular growth modes in the droplet height relaxation curve were detected in every oscillation cycle during the early spreading stages. It only took three and four oscillation cycles for a water droplet on the glass and quartz substrates, respectively, to dissipate its energy and reach its equilibrium state. However, it took 72 and 28 oscillation cycles for a water droplet on the Teflon and paraffin substrates, respectively. Moreover, several other new phenomena were also observed.

Interfacial temperature measurements, high-speed visualization and finite-element simulations of droplet impact and evaporation on a solid surface

“…For instance, using flash videography with 150 ns light pulses, Attinger et al [21] visualized the impact, spreading, oscillations and solidification of a molten solder microdroplet, a process that occurs in less than 300 µs. Another way to record the evaporation of microliter water droplets is to use a high-speed camera, as done by Mollaret et al [22] or Wang et al [23]. The images can then be processed to obtain evaporation parameters such as droplet volume, wetting angle, and wetted diameter.…”

Rejuvenated bouncing of non-Newtonian droplet via nanoparticle enwrapping

“…3 Therefore, it has aroused increasing research interest. [4][5][6][7][8] One of the most fascinating topics is to control the impact behavior of droplets, for instance, using tiny amount of polymer (weight $10 6 g/mol, in general) additives to prevent droplet rebound, which is essential in enhancing the pesticide spreading efficiency. The anti-rebound phenomenon is intrigue; however, the underlying physical mechanisms are still under debating.…”

Dynamic contact angle of water-based titanium oxide nanofluid

“…The fluid may be simple [1-3] or particulate such as paint, ink, or dye [4]. For many years, capillary flow of simple fluids has received considerable attention, and physics of capillary action is known for a long time [5-9].…”