A theoretical model has been proposed to incorporate internal flow mechanics to better predict the deformation and the resulting breakup of a liquid drop in a continuous uniform air jet in the multimode breakup regime. A Weber-number-dependent breakup criterion predicts the deformation of the drop at the time of the breakup, which occurs at the time the internal pressure at the drop equator exceeds internal pressure at the pole. This breakup criterion is used to determine an improved coefficient used in the Taylor Analogy Breakup (TAB) model. The TAB model is also extended to include the effects of turbulence within the drop. Hill vortices form within the drop as a result of viscous forces and flow around the drop. It is proposed that these vortices contribute to the deformation that eventually leads to the outer ring and smaller drop within the ring that is classic to multimode breakup. Instability analysis is used to model the breakup of the outer ring and predict the resultant droplet sizes. The model-predicted breakup times and ring breakup droplet diameter are compared with experimental results collected using digital in-line holography.

Characterization of the spray resulting from a 1 mm diameter liquid ethanol jet injection into a supersonic air crossflow is presented. The isentropic Mach number at the injection location is 1.94, while the momentum flux ratio is varied between 3 and 13. Steady and unsteady components of the penetration depth are retrieved using backlit imaging perpendicular to the spray at a frame rate of 20 kHz, coupled with a telecentric lens to accommodate the test section's width and ensure equal magnification through the spray's width. Spray width at specific axial locations downstream of injection is measured by imaging Mie scattered light from a planar laser sheet directed perpendicular to the flow direction so that a cross section of the spray is recorded by a camera placed at a known angle between camera axis and flow direction.

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