A linear temporal stability analysis of an inviscid incompressible gas jet injected with swirl into a co-flowing viscous liquid was conducted to study the growth of small three-dimensional disturbances that lead to the break-up of the gas jet. The presence of swirl was modeled as the velocity induced by an inviscid vortex. The primary flow parameters that governed the growth of the disturbances were the gas Weber number and the swirl number (ratio of the circulation to the product of the axial gas velocity and the radius of the jet). For small swirl numbers (less than O.S), the presence of swirl did not affect the growth of disturbances significantly. At higher swirl numbers, however, the growth rates of three-dimensional disturbances were significantly altered by gas swirl. Both the range of unstable wave numbers and the maximum growth rate were enhanced by the presence of swirl. Thus, the presence of gas swirl leads to the break-up of gas jets in liquids by three-dimensional disturbances, resulting in short break-up lengths and a wide distribution of resulting bubbles. The effects of gas swirl on the growth rates are documented for a wide range of conditions.
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