Fast droplets impacting liquid layer under a small angle: a numerical analysis of experimental observations.

• Droplet escapes initial crater at angles < 15° and remains inside it at angles > 45°. • Furrow is a chain of craters; between them, secondary entrainment may occur. • Surface tension, viscosity and reduced thickness dampen the craters inside the furrow. • Impact near wave crest leads to partial survival and detachment of the droplet. • Intensive bubble entrapment is not reproduced by the present model. In presence of a strong wind above a liquid surface, liquid droplets get accelerated and eventually hit the interface with a high speed under a small angle. Experimental studies demonstrate that such droplets may escape the initial crater and either get broken into secondary droplets in the air, or protrude along the interface, leaving behind agitated surface with entrapped bubbles. Here we aim at reproducing the observed phenomena in a numerical model based on Volume of Fluid technique using Basilisk package. On a flat interface, the impacting droplets partially escape the crater and get broken in front of it within the range of impact angles from 15° to 45°, in agreement to the experiments and simple theoretical considerations. In presence of waves, the escaping droplets fly into the air but, being adhered to the crater, get stretched and broken into secondary droplets. For smaller angles, the droplets escape the crater and glide along the interface. The gliding droplet creates a chain of small craters in its wake. The rims between the craters may grow and get scattered into secondary droplets. Large liquid viscosity and small thickness of the liquid layer suppress the growth of the craters and secondary entrainment. Bubble entrapment during such impacts most likely occurs due to crater collapse with trapping air inside. However, such air pockets are not formed systematically in the present model. This discrepancy requires further investigation. [Display omitted] [ABSTRACT FROM AUTHOR]