Effect of Compressibility and Density Ratio on Two Phase Shear Layers*

Atomization occurs when a liquid jet from a nozzle is discharged into a stagnant or moving gas causing the gas-liquid interface to become unstable and break up into a collection of droplets. The objective is to simulate a simplified problem of planar two-phase mixing layer between a co-flowing liquid and high-speed gas stream in a compressible regime. A 6^th order staggered, compact finite difference method with the 5-equation model, 2^nd interface sharpening, localized artificial diffusivity, and no filtering is found to be robust for multiphase flows particularly high-density ratios with shocks and to have excellent agreement with linear stability theory when finite interface thickness effects are included¹.  The effect of compressibility is explored in the nonlinear regime in 2D simulations varying gas Mach number for a moderate gas Reynolds number and high gas Weber number. Overall, gas Mach number reduces the interface perturbation, growth rates, and momentum thickness  at density ratio of 10 but does not significantly impact these attributes at density ratio of 1000. Preliminary simulations of the shear layer breakdown in 3D are planned.