Experimental investigation of the impaction of water droplets on cylindrical objects

The impaction of water droplets on isothermal cylindrical wires has been in vestigated experimentally in the present study. Mono-size droplets of 110, 350 and 680 mu m in diameter were generated using piezoelectric droplet gen erators. The effects of droplet velocity and wire size were varied parametr ically to reveal the impacting phenomena. Typical modes of the impaction ou tcome are disintegration and dripping. For droplets impacting on small wire s, finer drops are disintegrated if the impacting droplet velocity is high, and larger dripping drops are observed if the velocity is low. For droplet s impacting on large wires, bigger pendent drops are gradually formed which would eventually detach from the wires under the influence of gravity. In addition, droplets impacting on wires with waxy surface generate smaller dr ipping drops than that of the non-waxed wires. A non-dimensional regime map and new formulations in terms of the droplet Weber number, the wire Bond n umber and the size ratio of the wire diameter to incoming droplet diameter have been established to identify the regime for each mode of outcome and t o predict the size of the dripping drops within the experimental limits. (C ) 1999 Elsevier Science Ltd. All rights reserved.