Aerodynamically driven coalescence of drops on parallel fibers

In fog harvesting and filtration, drops continuously impact or condense on the fibers of a mesh. Efficiency is sometimes limited by inadequate drainage of the collected liquid. In such situations, controlled coalescence of the accumulated drops would be helpful to achieve higher efficiencies. Building on previous work, we study regimes of interaction of drops on fibers in a cross flow using a model system of fibers under tension and perpendicular to an air flow. Our parameter space straddles critical and subcritical conditions for flow past a circular cylinder. Our experiments also address two regimes of steady asymmetry present for flow past a sphere at intermediate Reynolds numbers that were identified by linear stability analysis. We relate our findings regarding coalescence to the aforementioned transitions and the aspect ratio of the drops. Our findings will allow for improved designs for facile coalescence and drainage.