Simulation of ligament mode breakup of molten slag by spinning disk in the dry granulation process

This paper performed the numerical investigations on the physical mechanism of ligament mode breakup of molten slag at the spinning disk edge by volume of fluid methodology, the piecewise line interface calculation scheme is utilized to track the air-slag interface location. Ligament spacing, length and tip diameter, and droplet size have been analyzed, a ligament spacing model for viscous fluids is developed theoretically based on Rayleigh Taylor instability analysis. Viscosity always produces a damping effect on the ligament spacing and the appearance of ligament. The ratio of ligament length and tip diameter is proportional to We^0.447. Due to the circumferential surface tension, the ligaments tend to a pinch-off type droplet formation mode, and the breakup of ligament is a final result of destabilization of capillary waves. Due to ligament stretching caused by centrifugal effect, the pinch-off capillary wavelength is about 2.2-3.1 times of the ligament tip diameters. However, the actual dominant mode is the short-wave mode driven by propagative capillary wave from the ligament tip.