The connection between sound production and jet structure of the supersonic impinging jet

Abstract

An experimental investigation into the sound-producing characteristics of moderately and highly underexpanded supersonic impinging jets exhausting from a round convergent nozzle is presented. The production of large plate tones by impingement on a square plate with a side dimension equal to 12 nozzle exit diameters is studied using random and phase-locked shadowgraph photography. Discrete frequency sound is produced in the near-wall region of the jet when a Mach disk occurs upstream of the standoff shock wave. Tones cease when the plate distance is approximately 2.2 free-jet cell lengths and the first and second shock waves are located in the free-jet positions. The production of impulsive sound appears to be associated with the collapse of the standoff shock wave during a portion of the oscillation cycle. Results from unsteady plate-pressure measurements indicate that plane-wave motion occurs in the impingement region and a secondary pressure maximum is observed on the plate adjacent to the flow region where sound appears to originate.

Flow Features near Plate Impinged by Ideally Expanded and Underexpanded Round Jets

“…On the contrary, only two or three dominant tones are found for the nonideally expanded jets, as already noted in various experimental studies [6,7,34,35].…”

Self-excited oscillations of a high-speed impinging planar jet

“…Various aspects of the feedback excitation mechanism for the subsonic axisymmetric case have been investigated by Ho and Nosseir (1981), Nosseir and Ho (1982), Tam and Ahuja (1990) and Panickar and Raman (2007), among many others. Extensive work on the axisymmetric case involving supersonic flows has been performed by Henderson and Powell (1993), Krothapalli et al (1999) and Henderson (2001). In addition, the planar impinging jet case using supersonic jets has received some attention in the literature, e.g.…”

Flow Field and Acoustic Investigations of the Launch Vehicle Environment during Lift-off

“…Apart from diverting the flow of the jet, the jet deflectors also influence the noise radiation from the jet. Studies on the acoustics of a single jet impinging on a flat plate [29][30][31][32][33], showed presence of new noise sources in addition to the conventional ones associated with undeflected jets. However, the primary goal of these studies had been to reduce the noise from aircraft engine exhausts.…”