Influence of nozzle conditions and discrete forcing on turbulent planar jets

Planar turbulent jets are of great interest in a broad range of engineering applications such as combustion, propulsion, and environmental hows. The influence of the turbulence intensity at the inflow and the shear-layer momentum thickness, as well as the effects of discrete forcing on the initial development of the jet, are studied computationally. It is found that the inflow fluctuation intensity and shear-layer momentum thickness have significant impact on the initial growth of the jet. Higher fluctuation intensity and thinner shear layers lead to more rapid growth of the jet with an asymptotic approach of the centerline turbulent kinetic energy to the self-similar values. The influence of the shear-layer thickness suggests a strong dependence of the initial growth on the shear-layer instabilities near the nozzle. Two-dimensional discrete forcing enhances the growth and two-dimensionality of the large-scale structures in the near field of the jet. However, significant three-dimensional small-scale structures coexist with the large-scale structures. The influence of the forcing is rapidly lost downstream as the large-scale structures break down.