Mechanisms of the breakup of liquid jets

A general theory of the onset of breakup of liquid jets in an ambient gas is given. The theory is based on the linear stability analysis of a viscous liquid jet with respect to spatially growing disturbances. The three independent parameters in the theory are the Reynolds number /?, the Weber number We, and the gas-to-liquid density ratio Q. The numerical results obtained from a single characteristic equation over a wide range of the parameter space reveal that there are two fundamentally different mechanisms of the jet breakup. The first is the capillary pinching that breaks up the jet into segments. The second is the capiUary wave resonance with the gas pressure fluctuation that generates droplets much smaUer than the jet diameter. An argument based on the boundary-layer instability theory is used to demonstrate that the shear waves at the liquid-gas interface plays a secondary role in the jet breakup.