Quantification of Hydrometeor Breakup in High Weber Number Flows

High-speed vehicles that encounter hydrometeors experience intense aerodynamic loading and surface erosion arising from hydrometeor deformation, fragmentation, and mist generation in the post–shock flow. This work quantifies the aerobreakup of non–spherical droplets at ultra high Weber numbers ($We>10^5$) using megahertz rate diffuse backlight extinction imaging synchronized with railgun impacts. The results show that droplet deformation, liquid volume fraction, and surface area evolution collapse to a consistent scaling with the initial Weber and Ohnesorge numbers, indicating that the breakup dynamics are dominated by inertial-to-capillary interactions. Accounting for initial droplet aspect ratio reveals that geometry influence the droplet deformation and onset of atomization, after which all droplets converge toward a common, quasi–steady aerodynamic configuration. Empirical fits based on these measurements demonstrate that the complete geometric evolution, from bulk deformation to mist generation, can be described by a single characteristic parameter, enabling a simplified prediction of catastrophic hydrometeor breakup.