Damping and Droplet Deformation: A Cantilever-Droplet System

The interactions of a cantilever-droplet system represent an elaborate mechanism that is applicable to many interdisciplinary fields. One such application is the study of raindrop impact on plant leaves. Previous studies have focused on the positive correlation between the length of an elastic, hydrophilic cantilever and its vibrational damping ratio, however, we observe that shorter cantilevers(< 100 mm) deviate from this trend. To investigate this, we impacted thin polycarbonate beams of varying lengths with a water droplet of precisely controlled momentum, and used high-speed cameras to record the vibrational responses. The damping ratio of the beams exhibits significant dependence on beam length prior to ~50 mm, and a flattening droplet is also observed during the upward motion of beams longer than ~45 mm. We hypothesize that both phenomena are due to the interplay between a phase shift in beam and droplet oscillations (for beams shorter than ~45 mm), and an acceleration difference depending on increasing beam length. These beam-droplet interactions can be helpful for future developments in energy-conversion techniques by understanding how energy could be harvested from raindrops.