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Atomization and Sprays

Journal of the International Institutes for Liquid Atomization and Spray Systems

ISSN for PRINT: 1045-5110

Institutional price:	$787.00
Issues per year:	8

Best Paper Award Selection - Editorial Board Site

2006, Volume16

159 pages

Issue price - $80.00

EFFECTS OF AIR ON SPLASHING DURING A LARGE DROPLET IMPACT: EXPERIMENTAL AND NUMERICAL INVESTIGATIONS

Richard A. Jepsen
Mechanical Environments, Sandia National Laboratory, P.O. Box 5800, Albuquerque, New Mexico 87185-1135, USA

Sam S. Yoon
Mechanical Engineering Department, Korea University, Anamdong, 5-Ga, Sungbukgu, Seoul, 136-713, Korea

Byron Demosthenous
Applied Diagnostics, Sandia National Laboratory, P.O. Box 5800, Albuquerque, New Mexico 87185-1135, USA

ABSTRACT

Recent studies have shown the importance of air in causing the splashing phenomenon (L. Xu, W. Zhang, and S. R. Nagel, Phys. Rev. Lett., vol. 94, 184505, 2005) and the subsequent finger formation for a large-scale liquid droplet impact. The experimental investigation and the relevant computational modeling have been performed to obtain additional insight on the large-scale splashing phenomenon. Previous modeling efforts did not consider the effect of air by starting the simulation at the time of droplet-liquid contact with the substrate. Here we start the simulation using the volume of fluid method at a location one diameter upstream so that the compressed air effect due to a falling droplet is properly taken into account. Both the experiments and simulations demonstrate that the displaced air obtains momentum from a falling droplet and induces a vortex motion right above the contact surface. The splashing (or ejection) occurs when the initial edge of the impacting and spreading liquid is entrained into the displaced and accelerated air. It is also hypothesized that the perturbation generated during the splashing process is radially propagated and is the fundamental instability that eventually forms fingers at the rim of the spreading liquid.