Water entry of cups and disks

• DOI: 10.1017/jfm.2023.330
• Publication Date: 2023-05-16T10:53:13Z
• Authors: Jesse Belden; Nathan B. Speirs; Aren M. Hellum; Matthew Jones; Anthony J. Paolero; Tadd T. Truscott
• Keywords: Dimensionless quantity; Drop Impact; Air entrainment; Entrainment (biomusicology); Solid surface

It is known that the water entry of a body with recessed, cupped nose can suppress splash and air cavity typically observed for solid (Mathai, Govardhan & Arakeri, Appl. Phys. Lett. , vol. 106, 2015, 064101). However, interplay between captive gas in cup, quite subtle has not been thoroughly explored. Here we study dynamics associated vertical cups find variety regimes over range Weber numbers ( $We_D$ ) dimensionless cup depths. Our parameter space spans transition slow-developing cavities long closure times (low to fast-sealing (high ). An important dynamic event evacuation trapped from within which drives ensuing behaviour. Through modelling, predict conditions evacuating inflates opens atmosphere versus inflating submerged suppresses entrainment above surface. We also compare our findings impact phenomena flat disks, entrap on front surface similar cups. In doing so, reveal sensitivity disk behaviour angle, show disks share common regime cups, thin quickly seals body. deduce mechanisms by increasing depth delays seal time this regime. These may fact promote or growth, depending conditions.