The fragmentation of liquid jets within gaseous crossflows finds numerous applications in both natural and industrial situations. The thermophysical properties of the liquid and gaseous media significantly influence the instability waves along the liquid jet column, the breakup mechanisms, and the resulting droplet size and velocity distributions. The viscosity and density of liquid and gaseous phases can vary widely based on the application. In plasma spray processes, the gaseous Reynolds number and the liquid-to-gas density ratio reach approximately 30 and 12 000, respectively, well beyond the typical ranges in engines and wind tunnels. This study employs numerical simulations to gain insights into the breakup mechanisms within these unique and unexplored conditions, aiming to take a step towards comprehending the intricacies of liquid jet breakup in thermal spray environments. The finite volume scheme has been used to solve the incompressible variable-density Navier-Stokes equations, and a volume of fluid approach has been utilized to track the gas-liquid interfaces. The study presents a range of findings, including qualitative results such as instantaneous snapshots and liquid jet cross-section shapes, alongside quantitative data on breakup point locations, surface wavelengths, pressure distribution, and jet trajectory. Our observations demonstrate that a low momentum flux ratio predominantly drives the transition to Kelvin-Helmholtz instability, with high gaseous viscosity acting as a secondary factor that enhances liquid column breakup in plasma-like crossflow conditions. This behavior contrasts with the Rayleigh-Taylor instability, which is commonly reported at relatively high momentum flux ratios, high-density ratios $(\sim 1000)$, and high gaseous Reynolds numbers.

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• Atomization
• Kelvin-Helmholtz instability
• Multiphase flows
• Vortex dynamics
• Volume of fluid method