The present investigation considers the stability of a mixing layer when a wake or a jet component is present. This components represent a finite thickness spliter plate or a fuel jet issuing from a nozzle at the center of a mixing layer. Previous investigations available in the literature show that superposed free-shear layers are more unstable than the simple mixing layer. Compressibility and different chemical species on the upper and lower streams also have an impact on the stability of the shear layer. Those investigations used canonical hyperbolic tangent and Gaussian profiles for the base flow. The aim of the present investigation is to extend results available in the literature for the stability of hyperbolic tangent and Gaussian profiles to the stability of superposed free-shear layer profiles obtained through solution of the binary compressible parabolic boundary layer type equations. The study is based on the local normal mode stability analysis using the compressible version of the Rayleigh equation for a binary system. The more realistic laminar flow profiles allows the investigation of variable viscosity, conductivity and other properties across the shear layer. The effects of temperature, and velocity ratios are taken into account with the correct density variation for a mixture of hydrogen and oxygen, but the model can be used to investigate any other gas mixture of interest.
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