2 research outputs found
Sweeping by Sessile Drop Coalescence
During coalescence of liquid drops contacting a solid, the liquid sweeps
wetted and solid-projected areas. The extent of sweeping dictates the
performance of devices such as self-cleaning surfaces, anti-frost coatings,
water harvesters, and dropwise condensers. For these applications, weakly- and
non-wetting solid substrates are preferred as they enhance drop dynamical
behavior. Accordingly, our coalescence studies here are restricted to drops
with contact angle 90{\deg} 180{\deg}. Binary sessile drop
coalescence is the focus, with volume of fluid simulations employed as the
primary tool. The simulations, which incorporate a Kistler dynamic contact
angle model, are first validated against three different experimental substrate
systems and then used to study the influence of solid wettability on sweeping
by modifying . With increasing up to 150{\deg}, wetted
and projected swept areas both increase as drop center of mass heightens. For
150{\deg}, coalescence-induced drop jumping occurs owing to
the decreasing wettability of the substrate and a focusing of liquid momentum
due to the symmetry-breaking solid. In this regime, projected swept area
continues to increase with while wetted swept area reaches a maximum
and then decreases. The sweeping results are interpreted using the mechanical
energy balance from hydrodynamic theory and also compared to free drop
coalescence.Comment: 17 pages, 10 figures, 3 tables, to be published in Eur. Phys. J.
Special Topics: Challenges in Nanoscale Physics of Wetting Phenomen