A fully non-linear model for atomization of high-speed jets

A non-linear model has been developed to assess the time evolution of an axisymmetric liquid jet using a boundary-element method. Vorticity transported from the boundary layer in the orifice passage to the free surface is modeled using a potential ring vortex placed at the orifice exit plane. The vortex strength is uniquely determined from the Kutta condition and information regarding the boundary layer thickness at the orifice exit plane. It is shown that primary breakup can occur even in the absence of the gas phase. Using a secondary stability analysis after Ponstein [Appl. Scientific Res. 8 (1959) 425], the size of the droplets is estimated based on the size of the ring-type structures shed from the periphery of the jet. Computed droplet sizes are in reasonable agreement with experimental data, although turbulence effects obscure some comparisons.