This paper describes the experimental study of the noise generating characteristics of high-temperature, shock-containing jets emanating from conic-section, converging-diverging (C-D) nozzles. Conic C-D nozzles consist of two conic sections, one contracting and the other expanding, joined to form a supersonic nozzle with a very sharp radius of curvature at the nozzle throat. An experiment is co...

A wave-packet ansatz is used to model noise generation by organized, large-scale structures. The spectrum of the acoustic field is expressed in terms of two-point space-time correlations of hydrodynamic pressure on a conical surface surrounding the jet plume. The surface is sufficiently near the turbulent flow region to be dominated by hydrodynamic disturbances, yet sufficiently far that the wa...

Through the sound spectrum analysis, this paper indicates that the noise peak frequency comes from mechanical shock, investigating the frequencies of noise sources, the noise peak frequency is found --the impact pairs of the valve plate and the spring~ The cause to raise the noise is on the phenomenon detachment between the valve plate and the spring. For this reason the valve plate produces hi...

Turbulence statistics that are relevant to jet noise modeling but difficult to measure in experiments are computed using a previously validated simulation database of a Mach 0.9 cold jet. Initial focus is on fourth-order statistics that are at the core of acoustic analogy based models built on both the Lilley and Lighthill equations. Common simplifications of fourth-order correlations based on ...

This research is motivated by the need for physical models for the jet noise source to be used in practical noise prediction schemes for propulsion-airframe integration concepts. The emphasis is on jets with high-subsonic velocities typical of modern turbofan engines. The basis for the source model is an amplitude-modulated traveling wave the wavepacket. Its parameters are determined by minimiz...

A nonlinear interaction model is used to study sources of sound in jets. The model uses quadratic interactions of instability modes, which are obtained by solving the linear parabolized stability equations. Source terms involving nonlinear interactions are evaluated and a linear wave equation is solved with direct injection of the source terms. Thus the complete method solves only linear partia...