Behavior of a water droplet in silicone oil with electric field formed by wire-cylinder electrode system

Abstract

This study has been carried out experimentally to reveal motion behaviors of a water droplet in silicone oil with an electric field. The study used the radial electric field formed by the inner surface of a metal cylinder, and a thin metal wire which had been installed coinciding with the central axis of the cylinder. After a water droplet was supplied between the electrodes, a high voltage of 10 - 16 kV DC was applied between the electrodes. The motion behavior of single water droplet in each experiment was recorded using a high-speed video camera and then observed precisely and analyzed. As a result, it was observed that the water droplet reciprocated repeatedly between each electrode. Detailed observation revealed that the water droplet always stopped a few millimeters in front of the wire electrode, and the water droplet interface contacted and exchanged charges by forming an interface with a shape like a Taylor cone with a pointed tip extending to the surface of the wire electrode. The contact time of the water droplet on each electrode was approximately 5ms in contact with the wire electrode and 25 ms with the inside surface of the cylindrical electrode. From these results, it was clarified that the reciprocating behavior under a non-uniform electric field and the contact behavior for each electrode were different, and especially, water droplets stopped just before the wire electrode. By using the general solution of the equation of motion of the water droplet, its charge quantity was estimated through four view points, and calculated velocity by use of each calculated charge. The evaluation was carried out by comparing the calculated result with the experimental value.

Keywords

• liquid-liquid direct contact
• non-uniform electric field
• water droplets
• silicone oil
• droplet motion