ID 268

Ligament dynamics of a radially expanding circular liquid sheet

 

Abstract:

The present work analyzes the successive events leading to ligament formation during the disintegration of a radially expanding unstable circular liquid sheet. Further, the effects of surface tension and aerodynamic forces on the ligament breakup and spherization into droplets are considered. The circular liquid sheet is obtained by an orthogonal impingement of a cylindrical liquid (water) jet on a cone-disc deflector. The experiments are carried out at different Weber numbers over the range of 997<We_jet<7473. Time-resolved simultaneous high-speed volume laser induced fluorescent (VLIF) of the side and top views of the liquid sheet at 6 kHz repetition rates is conducted. The ligaments originate from two physical sites of liquid sheet. The first region is at the leading edge of a liquid sheet, where the long filigree-like threads of a continuous sheet break up due to Plateau-Rayleigh instability. Since it is a radially expanding liquid sheet, it is subjected to sheet thinning phenomenon, which creates perforations on it. The second region is at the coalescence of two or more perforations. A liquid bridge forms at the rims/boundaries, which is stretched due to unbalanced surface tension force and produces a wide spectrum of ligaments and droplets behind. Further, it is noted that the ligaments generated from the leading edge are larger in size as compared to those formed by coalescence of perforations. The correlations between ligament length and thickness with droplet Sauter mean diameter (SMD), and thus their volumes, are obtained to quantify the breakup and spherization of the ligaments.