EXPERIMENTAL INVESTIGATION OF JET BREAKUP AT LOW WEBER NUMBER

An experimental investigation on the disintegration of circular liquid jets, ejected into a stagnant ambient atmosphere at low Weber number, is presented. The process of breakup of the liquid jet was captured using real-time image processing with a high-speed digital camera system. Experiments were conducted for a range of Weber numbers from 5 to 110 using 12 stainless steel needles, whose diameters ranged from 0.279 to 1.753 mm, as nozzles to issue the liquid jet. Six viscous Newtonian liquids (water, ethylene glycol, propylene glycol, and glycerin water mixtures) with surface tension varying from 72.8 to 36.6 mN/m and viscosity ranging from 1 to 58 mPa-s were used. Based on the Weber number of the issuing jet, two types of jet breakup modes were observed, viz., dropwise and ligamented. At lower Weber numbers the jet is seen to disintegrate into droplets whereas at higher Weber numbers large ligaments are formed that further break up into drops. By scaling different forces acting on the jet, it is shown that the breakup length depends on the Weber number, Reynolds number, and Bond number as well as the dimensionless nozzle diameter. A correlation to predict the breakup length at low Weber numbers (We < 100) for Newtonian liquids is proposed. The predictions of breakup length from the correlation match well with the data available in the literature as well as measurements from this study.