Experimental investigation of drag coefficient of free-falling deformable liquid gallium droplet

In this article, the effect of shape and deformation on the drag coefficient of a free-falling liquid gallium droplet in water in a terminal state is investigated experimentally. The temperature of the dispersed and continuous liquid was varied in order to examine the effect on the liquid-metal droplets. The falling droplets were imaged using a high-speed camera, and a simple model was developed to predict drag coefficient over a Reynolds number range of 10(3) < Re < 10(4). The drag coefficients of the deformed liquid gallium droplets were found to be larger than that associated with a solid sphere and the associated Weber number was below 4.5. It was found that the shape of all droplets in our experiment were oblate spheroid. A correlation has been established to predict the aspect ratio of a liquid gallium droplet moving in quiescent water. The deformation is highly dependent on interfacial surface tension and inertial force, while the viscosity ratio and pressure distribution have negligible effect.