Concurrent Droplet Coalescence and Solidification on Surfaces With Various Wettabilities

An experimental study is performed to analyze the shear driven droplet shedding on cold substrates with different airflow speeds typical of those in the flight conditions. Understanding the mechanism of simultaneous droplet shedding, coalescence, and solidification is crucial to devise solutions for mitigating aircraft in-flight icing. To mimic this scenario, the experimental setup is designed to generate shear flow as high as 90 m/s. The droplet shedding at high-speed is investigated on a cold surface (0 and −5 °C) of different wettabilities ranging from hydrophilic to superhydrophobic. Result analyses indicate that on a hydrophilic substrate, the droplets form a rivulet, which then freezes on the cold plate. In contrast, on the superhydrophobic surface, there is no rivulet formation. Instead, droplets roll over the substrate and detach from it under the effect of high shear flow.

Shear-driven droplet coalescence and rivulet formation

Icing on aerodynamic surfaces occurs due to the accumulation of rain droplets when the surrounding temperature is below the freezing temperature. It is well known that icing phenomenon alters the aircraft aerodynamic forces and may cause serious damage. Therefore, studying water droplet behavior, such as shedding and coalescence serves as the primary step which can lead to understanding the fundamental physics of aircraft icing. Hence, in this study an experimental approach is used to investigate the shear-driven droplet shedding and coalescence on a hydrophilic substrate which can serve as the building block for the formation of rivulets.

Concurrent Droplet Coalescence and Solidification on Surfaces With Various Wettabilities

Experimental study is performed to analyze the shear driven droplet shedding on cold substrates with different shear flow speeds typical of those in the flight conditions. Understanding the mechanism of simultaneous droplet shedding, coalescence and solidification is crucial to devise solutions for mitigating aircraft in-flight icing. To mimic this scenario experimental set up is designed to generate shear flow as high as 90 m/s. The droplet shedding at high speed is investigated on a cold surface (0 and −5 °C) of different wettabilities ranging from hydrophilic to superhydrophobic. Result analyses indicate that on a hydrophilic substrate, the droplets form a rivulet which then freezes on the cold plate. In contrast, on the superhydrophobic surface, there is no rivulet formation. Instead, droplets roll over the substrate and detach from it under the effect of high shear flow.