Water-drop-surface-wave interactions

Splashes of water drops on liquid surfaces are important phenomena in several fields, notably the geosciences where they determine some transport rates and atmospheric-electrification processes. Splashes on smooth liquid surfaces have been well described, but in actual field situations splashes usually occur on disturbed surfaces. This report describes two new types of splashes that occur in the presence of surface waves. These were studied with drops falling from a buret into the center of a circular battery jar filled with water. Each drop interacted with the reflected waves produced by the preceding drops. We find that a drop impacting near the time of a crest of the surface wave produces intense surface waves and a diminutive Rayleigh jet. A drop impacting near the time of a trough of the surface wave produces weak surface waves but an unusually high Rayleigh jet. The great difference in these two types of interactions implies that any study of transportation or electrification due to splashes must include drop surface-wave effects.