Transition between coalescence and bouncing of droplets on a deep liquid pool

Abstract

This study focused on the bouncing of sub-millimetric droplets (below 0.7 mm) of three different fluids, distilled water, technical ethanol and 1-propanol on a deep liquid pool of the same fluids. Four different flow regimes including low-energy-collision coalescence, bouncing, high-energycollision coalescence, and partial coalescence were observed in the experiments. These regimes were plotted in velocity-diameter diagrams, which showed that there was a diameter limit, D ≈ 0.2 mm, above which the low-energy-collision coalescence was inhibited. 1964). Based on stable restitution coefficients, which varied with fluids, the effects from both viscosity and surface tension were discussed. Further, a correlation (K = We · Oh −0.58 ) was generalized to characterize the two transitions between coalescence (both high-energy-and low-energy-collision types) and bouncing, and a comparison with the model and data of Huang and Zhang (in Petrol Sci 5:62-66, 2008) showed that the generalized model characterized the coalescence-bouncing threshold well for the experimental fluids in the present study and oil with much higher viscosity.

A robust method for calculating interface curvature and normal vectors using an extracted local level set

“…Experimental results (top) and simulation results (bottom) for a 0.18 mm water droplet falling through air and impacting a deep pool of water at 0.29 m/s.Figure (a)is reprinted from[42], Copyright (2011), with permission from Elsevier.…”

Rebounding Droplet‐Droplet Collisions on Superhydrophobic Surfaces: from the Phenomenon to Droplet Logic

“…However, they did not observe rebounding collisions,4 illustrated in Figure 1 (bottom). Beyond the grazing collisions of droplets in free fall, bouncing has only been observed for a water droplet falling on a second droplet that wets a solid surface,5 in a similar fashion as a droplet can bounce when falling on a large pool of water 6, 7. Here we present the first demonstration of rebounding droplet‐droplet collisions of water droplets colliding at all impact angles, by using a superhydrophobic surface to support moving water droplets, as illustrated in Figure 1.…”

Recoil of Drops During Coalescence on Superhydrophobic Surfaces

“…The frequency of bouncing diminished in pinning dominated surfaces. Zhao et al (2011) studied the transition between coalescence and bouncing of droplets when a drop is impinged on a liquid pool. The impinging drop merged with the liquid pool due to inertia in the coalescence regime.…”