Numerical investigation of liquid jet breakup in crossflow with high-density ratio and high gaseous viscosity

Liquid jets injected into crossflows characterized by very low gaseous Reynolds numbers, low momentum flux ratios, and extreme density ratios experience intensified bending, rapid surface stripping, and early column fracture compared with classical air-flow conditions. In this regime, ligament formation becomes strongly aligned with the crossflow, and instability waves wrap around the entire jet circumference rather than remaining on the windward side. Our results show that Kelvin--Helmholtz, rather than Rayleigh--Taylor, controls the breakup dynamics, with surface wavelengths remaining independent of the Weber number.