The Taylor-Analog-Breakup (TAB) model [65] is used to model the secondary breakup of the droplets in hollow-cone sprays. The TAB model exploits an analogy between a distorted droplet and an oscillating spring-mass-system. The external forces acting on the mass, the restoring force of the spring, and the damping force are analogous to the gas aerodynamic force, the liquid surface tension force, and the liquid viscosity force, respectively. The force balance on the droplet gives
 | (6–66) |
where t is time, y is the normalized (by the drop radius) drop distortion parameter, σ is the surface tension coefficient, and the subscripts g and l denote the gas and liquid phase, respectively. It is assumed that breakup occurs if and only if y > 1 [65] . When this condition is satisfied, the droplet breaks up into smaller children droplets with sizes determined by an energy balance taken before (subscript 1) and after (subscript 2) the breakup as
 | (6–67) |
In Ansys Forte’s TAB model used in the present study, the droplet size after breakup, r 2, is assumed to follow a Rosin-Rammler distribution [4] .