A universal modelling approach of drop fragmentation after head-on drop collisions is presented. In this approach, the colliding drops are seen as liquid springs that coalesce, compress and relax, leading the merged drop to break up if it reaches a critical aspect ratio. Combining energetic balance of the compression and relaxation phases with a Rayleigh-like criterion, we deduce the fragmentation threshold velocity for the collision of two and three drops of the same liquid and of two drops of immiscible liquids. Predictions and experimental results obtained for these three kinds of collisions using various liquids and drop sizes are found to be in good agreement over a wide domain whose boundaries are discussed.
Head-on collisions of binary water droplets at high Weber numbers are studied by means of direct numerical simulations (DNS). We modify the lamella stabilization method of Focke & Bothe (J. Non-Newtonian Fluid Mech., vol. 166 (14), 2011, pp. 799-810), which avoids the artificial rupture of the thin lamella arising in high-energy collisions, and validate it in the regime of high Weber numbers. The simulations are conducted with and without initial disturbances and the results are compared with the experimental work of Pan et al. (Phys. Rev. E, vol. 80 (3), 2009, 036301). The influence of initial white noise disturbance on the collision dynamics is identified and good agreement between the simulation results and the experimental results is obtained when the initial noise disturbances are properly exerted. In order to include the stochastic nature of the disturbance, we conduct several simulations with white noise disturbance of same strength and average the spectrum diagram for the unstably developing rim of the collision complex. We show that the magnification of rim perturbation can be predicted by Plateau-Rayleigh theory over a long time span.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.