Aeroacoustic resonance and self-excitation in screeching and impinging supersonic jets – A review

Abstract

Supersonic jets, particularly shock-containing jets, often exhibit high-intensity, discrete-frequency acoustic tones. These tones are the signature of an aeroacoustic resonance loop established by the flow. This paper considers two of the classical forms of supersonic jet resonance: screech in shock-containing free jets and tones generated by the impingement of a jet against a surface. The first half of the paper provides a historical perspective on research into both forms of resonance, ranging from the seminal works of Alan Powell to recent contributions from high-fidelity numerical simulation, experiment, and stability theory. The second half of the paper provides a critical assessment of current understanding around the four processes that characterize jet resonance: a downstream propagation of energy, an acoustic generation mechanism, an upstream propagation of energy, and a receptivity mechanism.

Modelling of jet noise: a perspective from large-eddy simulations

“…Tam [72,73], and Raman [74] have provided a critical review of jet screech research (also see [75] for an update). They note that existing models of screech are capable of predicting the screech tone frequency, following the notion of a screech feedback loop pioneered by Powell [76], but no simple models capable of predicting the screech amplitude exist as yet.…”

Acoustic feedback loops for screech tones of underexpanded free round jets at different modes

“…The screech tone first observed by Powell (1953) has a high-amplitude discrete frequency. The development of the understanding of the screech tone is summarized in some detailed reviews, such as Raman (1999) and Edgington-Mitchell (2019). Based on the schlieren flow visualization, Powell (1953) suggested that the generation of the screech tone is due to an acoustic feedback cycle near the nozzle exit.…”

Self-oscillatory flow in the Hartmann resonator – Numerical simulation

“…It is worth noting that in many self-oscillatory processes in gas jets, either free or impinging, the key role is played by the feedback loop consisting of four components comprehensively described in recent overviews. 36,37 They include disturbances traveling downstream in the jet itself, sound production by the disturbed jet, the propagation of disturbances upstream, toward the nozzle, and the closure of the loop by excitation of new disturbances in the jet shear layer near the nozzle lip. Thus, this idea turned out to be very fruitful in developing the theory of the screech (discrete tone radiation) of free supersonic jets discovered by Powell as long ago as in 1953 38,39 and confirmed later in many experiments.…”

“…An expose of his views is given in the above-mentioned recent paper by Edgington-Mitchell. 37 The key phrase of that expose is that, according to Powell, “feedback to the nozzle is not suggested to form part of the resonance process, but instead the plate and the standoff shock”.…”