Identification of Discrete Tonal Noise in Inclined Jet Impingement Using Pressure-Sensitive Paint

Abstract

This paper presents the utilization of fast-responding pressure-sensitive paint (fast PSP) to identify the discrete tonal noise generated in 55 deg inclined jet impingement. Cases of subsonic ( $\mathit{Ma}=0.80$ ) and supersonic ( $\mathit{Ma}=1.21$ ) jet impingement with nozzle-to-plate distances of $h/d=2,4,6$ , and 8 are investigated. The fluctuating wall-pressure field measured using fast PSP at high spatiotemporal resolutions provides unique insights into the discrete tonal noises associated with inclined jet impingement. A far-field microphone is used to validate the frequency of each tonal noise. The fast PSP data are subjected to spectral proper orthogonal decomposition, and the results demonstrate wave propagation along the wall surface. At $\mathit{Ma}=0.80$ , the circumferential propagation characteristics of the identified discrete tones correspond to the toroidal mode of the shear layer instability wave. As $h/d$ increases, the dominant tone decays, and several secondary tones disappear. Screech tones are identified at $\mathit{Ma}=1.21$ and $h/d=6$ and 8. Two perpendicular flapping modes are identified at the discrete tone for each $h/d$ , and the dominant flapping direction varies with $h/d$ .