Dynamics of free-surface mutually perpendicular twin liquid sheets and their atomization characteristics

Abstract

The radially expanding twin (circular and vertical) liquid sheets produced by impingement of a vertical cylindrical liquid jet onto a horizontally placed cone-disk deflector with a single slot were examined experimentally in the present work. Dynamics of these liquid sheets and the events leading to their breakup were studied by carrying out high-speed shadowgraphy simultaneously from side, front, and top views at a 5.4 kHz framing rate and for the jet Weber number (Wejet) range of 993 < Wejet < 3776. In the presence of the slot, the variation of the radial breakup distance of the circular sheet (Rb,CS) with Wejet changed from the monotonically decreasing trend (Rb,CS∼Wejet−0.44) to a nonmonotonic increasing and decreasing one. Furthermore, Rb,CS was found to be lowered by about 42% compared to the breakup distance Rb,CS,no-slot of the circular sheet for the no-slot deflector. The vertical sheet breakup distance (Rb,Vs) was found to increase monotonically with the slot Weber number Weslot0.44. Three primary sources of droplet production, namely, the lower and front edges of the vertical sheet and the rim of the circular sheet, were identified. The smallest droplets were seen to originate from the front edge (D32,FE) and the largest droplets from the lower edge (D32,LE) of the vertical sheet. The measured droplet diameters followed D32,LE∼Wejet−1/3 and D32,FE∼Wejet−1/4, whereas the droplets originating at the rim of the circular sheet followed D32,rim∼Wejet−2/3. The droplets at all three edges were found to depend more strongly on the ligament thickness than the ligament length. Following conservation of mass, a linear relation between the droplet diameter, D32, and the ligament thickness, tlig, at each edge has been obtained.