Abstract
In this paper, the mechanisms of breakup and frop formation of a radially thinning liquid sheet, which are attributed directly to the transition from laminar to turbulent flow, are described. A radial liquid film flow is generated by water discharge from one end of a cylindrical nozzle through a small gap present between the end of the nozzle and the flat surface of a disk. The liquid film spreads radially outward on the disk as a sheet, slowing from the edge of the disk into the air. Sudden laminar-turbulent transition occurs in the liquid sheet when the Reynolds number exceeds a critical value, resulting in both perforation and disintegration of the sheet under an extremely high Reynolds number. The breakup process through perforation, ligament formation and drop formation is observed both by zoom-in photography using a single pulse strobe and a steel camera and high-speed photography using a multipulse laser and a drum streak camera. These photographs clearly show that droplets a few tens of micrometers in size are produced from the liquid sheet. Flow conditions for the occurrence of atomization induced by the transition are also presented.
