Bouncing of polymeric droplets on liquid interfaces

Abstract

The effect of polymers on the bouncing behavior of droplets in a highly viscous, vertically shaken silicone oil bath was investigated in this study. Droplets of a sample liquid were carefully placed on a vibrating bath that was maintained well below the threshold of Faraday waves. The bouncing threshold of the plate acceleration depended on the acceleration frequency. For pure water droplets and droplets of aqueous polymer solutions, a minimum acceleration amplitude was observed in the acceleration threshold curves as a function of frequency. The bouncing acceleration amplitude for a droplet of a dilute aqueous polymer solution was higher than the acceleration amplitude for a pure water droplet. Measurements of the center of mass trajectory and the droplet deformations showed that the controlling parameter in the bouncing process was the oscillating elongational rate of the droplet. This parameter can be directly related to the elongational viscosity of the polymeric samples. The large elongational viscosity of the polymer solution droplets suppressed large droplet deformations, resulting in less chaotic bouncing.

Impact of Droplets on Liquid Films in the Presence of Surfactant

“…The outcomes of the impact process directly affect the performance of these applications or even cause catastrophic accidents, such as spray cooling of hot surfaces, icing on aircraft wings, and droplet-impact erosion on turbine blades. Despite the numerous studies in this area spanning more than a century, the droplet impact phenomenon is still far from being fully understood. − Many outstanding questions are still attracting attention, such as the origin of splashing, , the evolution of the air layers below the impacting droplets, , and the entrapment of air bubbles. , The impact process is complicated by many controlling parameters, such as the properties of the fluids (e.g., surface tension, viscosity, density, and rheology), the parameters of impact (e.g., droplet speed, impact angle, and film velocity , ), and the ambient condition (e.g., temperature and pressure). A range of phenomena may occur depending on the relative magnitude of these parameters, such as bouncing, , partial coalescence, − “crown” splashing, − and “prompt” splashing. , …”

“…1−3 Many outstanding questions are still attracting attention, such as the origin of splashing, 4,5 the evolution of the air layers below the impacting droplets, 6,7 and the entrapment of air bubbles. 8,9 The impact process is complicated by many controlling parameters, such as the properties of the fluids (e.g., surface tension, viscosity, density, and rheology 10 ), the parameters of impact (e.g., droplet speed, impact angle, and film velocity 11,12 ), and the ambient condition (e.g., temperature 13 and pressure 14 ). A range of phenomena may occur depending on the relative magnitude of these parameters, such as bouncing, 15,16 partial coalescence, 17−19 "crown" splashing, 20−22 and "prompt" splashing.…”

Surface roughness effect on droplet impact characterization: Experimental and theoretical study

“…Bouwhuis et al [27] investigated the size of the entrapped air layer applying interferometry and found a maximum at which air compressibility can be ignored. Gier et al [28] investigated how polymers can change the bouncing behaviour of droplets. They conducted an experiment in which an aqueous polymer solution droplets impact on a highly viscous and vertically shaken silicone oil bath.…”

Resonant and antiresonant bouncing droplets

“…An air layer separates the droplet from the vibrated surface which can therefore bounce vertically upon the liquid without coalescing. BD have the great advantage to transport some quantities of liquid without chemical contamination [2,3]. Moreover, BD may be either fragmented [4] or used to create controlled microemulsions [5].…”