Session D13: Drop Impact on Liquids

The impact of perfluorocarbon liquid drop onto a water pool

The impact of a drop onto a liquid pool portrays a plethora of interesting fluid-dynamical phenomena, from ejecta sheets to regular Edgerton crowns and Worthington jets.  When the drop has different composition than the pool, even more intricate forms can emerge.   Herein we use high-speed cameras to image the impact of a heavy perfluorocarbon liquid drop onto a water-pool.  The two liquids are immiscible and the drop is much heavier than water.  We focus on crater evolution, the formation of an internal air cylinder and the entrapment of a small bubble inside the drop during the crater-collapse.  We also show the formation of fine Worthington jets.   

Simulations of complex drop impacts on Interfaces

A numerical investigation of complex drop impact configurations is carried out using a hybrid front-tracking/level-set CFD solver. As part of this work, several key set-ups are investigated: oblique drop impacting a ‘deep’ pool, instantaneous and successive multiple drops impacting a ‘deep’ pool, and vertical drop impact on a thin film in the presence of surfactants. We highlight through these simulations the temporal evolution of asymmetrical crowns, craters, and jets obtained as a result of these complex drop impact situations. We provide both qualitative and quantitative comparisons with a number of experimental studies (e.g. Bisighini 2010, Gielen et al. 2017, Che and Matar 2017, Spiers et al. 2018).   

Investigation of the impact of a raindrop on oil slicks at the sea surface

 The various phenomena related to the impact of a water droplet on a layer of oil located at the surface of salted water are investigated. These conditions mimic raindrops on the sea surface after oil spill, which generate both oil dispersion in the water, and marine aerosol. Direct Numerical Simulations (DNS) are performed, using the GERRIS solver: the local dynamic grid refinement capabilities make it especially appropriate for the present application where multiple interfaces and a large number of droplets and bubbles are obtained. As the motivation of this project is the characterization of the small scale mechanisms involved in the droplet splash, behavior of the oil layer, and aerosol formation, it is mandatory to be able to resolve the very small scales of the flow (typically a few  microns) while ensuring a global computational cost in accordance with the current HPC resources. Validation of the numerical results is performed using the experimental data obtained previously at Johns Hopkins Univ. Then, the attention is focused on the analysis of the physical mechanisms that could not be extracted from the high speed visualization and the variation of the airborne droplets statistical size and behavior according to test conditions.