Experimental investigation of a nonspherical water droplet falling in air

Abstract

We experimentally investigate the shape oscillations of an initially nonspherical water droplet falling in air using high-speed imaging. We design a customized experimental setup that allows us to study the freely falling droplets of initially oblate/prolate/tilted configurations. The setup uses a pneumatic piston-cylinder arrangement and a superhydrophobically coated plate to propel a droplet upwards in air whose motion is then recorded using a high-speed camera. Due to the propulsive force imparted to the droplet, it undergoes oblate–prolate oscillations and eventually comes to rest at a maximum height, at which time the droplet has a zero vertical velocity and a nonspherical shape with an inclination to the horizontal. We study the effect of the initial aspect ratio and size of the droplet on its shape oscillations during its downward motion.

Experimental Study of the Effect of the Surfactant on the Single Bubble Rising in Stagnant Surfactant Solutions and a Mathematical Model for the Bubble Motion

“…2 cap 0.5 0.5 2 cap 0.5 0.5 (26) Equations 9, 14, 15, and 26 constitute a set of equations. There are four unknown variables, d, u, s, and ψ, in the above equations.…”

“…During the bubble rise, the bubble shape becomes irregular and oscillates considerably, especially for larger bubbles. Researchers conducted precise experiments to measure the bubble dynamics and derived semi-empirical or empirical models to predict the rising velocity, − shape deformation, − drag coefficient, − and rising path oscillation . From the models available in the literature, the impurity in liquids plays an important role in determining the bubble behavior.…”

Droplet size distribution in a swirl airstream using in-line holography technique

“…All these investigations are for straight airflow in the no-swirl condition. The deformation and breakup of a water droplet falling in air have also been investigated (Szakall et al 2009;Agrawal et al 2017;Balla, Tripathi & Sahu 2019;Agrawal et al 2020).…”

Influence of the pre-impact shape of an oil droplet on the post-impact flow dynamics at air–water interface

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