Impact of inlet gas turbulence on longitudinal and transverse instabilities in a two-phase mixing layer

Understanding the development and breakup of interfacial waves in a two-phase mixing layer between the gas and liquid streams is paramount to atomization. Due to the velocity difference between the two streams, the shear on the interface triggers a longitudinal instability, which develops to interfacial waves that propagate downstream. Depending on the injection and geometric conditions, the longitudinal instability can be convective instability, absolute instability controlled by surface tension, and absolute instability controlled by geometric confinement. As the interfacial waves grow spatially, transverse modulations arise, turning the interfacial waves from quasi-2D to fully 3D. The inlet gas turbulence intensity has a strong impact on the longitudinal instability. The dominant frequency and the spatial growth rate of the longitudinal instability are found to increase with the inlet gas turbulence intensity. The vertical interfacial motion induces Rayleigh-Taylor instability in the transverse direction. The dominant transverse wavenumber, scaling with the longitudinal frequency, also increases with the inlet gas turbulence intensity. Eventually, the sheet breakup dynamics and the statistics of the droplets formed also change accordingly.