Flow characteristics of the large scale wave-like structure of a supersonic round jet

A model is developed for the large scale coherent structure of subsonic and supersonic axisymmetric jets. A fluctuation in the jet flow is regarded as being separable into a time-averaged component, a periodic wave-like component and a random small scale component. The small scale fluctuation is viewed as both the driving and dissipative mechanism for the wave-like component. An energy balance model is developed which examines thinterchange of energy between the mean flow and the large scale motion. The effect of wave-like fluctuation amplitude on its own and the mean flow development is examined. Calculations of contours of equal pressure level in the jet near field are made. A model for the mechanism by which locally subsonic components of the wave-like structure may radiate noise to the far field is examined. The method for calculating the radiated noise is discussed.