Deegan group

Drop impact

Drop impact

The splash from the impact of a drop on a pool or thin layer of the same liquid arises from the emission, expansion and breakup of one or more sheets. This process has important implication for diverse physical processes such as gas transfer across the air-sea interface, combustion, and cooling. The spray pattern and the distribution of secondary droplet sizes is in general highly complex and has yet to be understood. The simplest case is the formation and breakup of a sheet which results in the spray pattern immortalised by Harold Edgerton’s Milk Coronet. We showed for the first time that this spatially regular splash is governed by the Rayleigh-Plateau instability, amplifying random microscopic noise. The number of secondary droplets is determined by the most unstable wavenumber of this instability.

We are now using X-ray imaging to examine the interior of a splash, concentrating on the jets formed during the impact event.


L. V. Zhang, J. Toole, K. Fezzaa, R.D. Deegan, "Evolution of the ejecta sheet from the impact of a drop with a deep pool", Journal of Fluid Mechanics 690 , 5 (2012). see also Focus on Fluids article.

L. V. Zhang, P. Brunet, J. Eggers, & R.D. Deegan, "Wavelength selection in the crown splash", Physics of Fluids 22, 122105 (2010).

R.D. Deegan, P. Brunet, & J. Eggers, "Complexities of splashing", Nonlinearity 21, C1–C11 (2008).

Updated March 21, 2012