Role of nozzle-exit boundary layer in producing jet noise

Karon, Aharon Z.; Ahuja, K. K.

doi:10.1177/1475472x221107375

Cited by 4 publications

(8 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It has been shown in a number of studies including by the current authors 13 that high-frequency jet noise reduces with thicker, more-developed nozzle-exit boundary layers. This indicates that if the boundary layer states of the jets compared in the any of the above studies were significantly different, the jet noise level differences observed could in-part be due to these differences.…”

Section: Introductionmentioning

confidence: 69%

Reynolds number and jet noise scaling

Karon,

Ahuja

2023

International Journal of Aeroacoustics

Self Cite

View full text Add to dashboard Cite

The Reynolds number and Mach number are classical quantities used to determine the similarity of aerodynamic flows. Existing studies on the role of Reynolds Number on jet noise show inconsistent results, casting doubt on how small a nozzle diameter can be for the classical jet noise scaling laws to hold. A systematic study was therefore undertaken to resolve this issue. The Reynolds number of jet flows was adjusted using a Mach number variation between 0.4 and 0.8, and nozzle-exit diameters of 0.25, 0.5, and two inches. When the jet noise measurements were normalized, spectral collapse was observed for the spectra across the whole Reynolds number range. It was found that the Reynolds number does not have a significant effect on jet noise, and jet noise can be scaled from even the smallest of nozzle to larger nozzles.

show abstract

Section: Introductionmentioning

confidence: 69%

Reynolds number and jet noise scaling

Karon,

Ahuja

2023

International Journal of Aeroacoustics

Self Cite

View full text Add to dashboard Cite

show abstract

“…An observation on nozzle size effect is made here based on the present and earlier results of. 5,45 The differences between the ASME design and the Conic cases are somewhat less pronounced with the 2 00 nozzles compared to the 1 00 nozzles in. 5 For example, in, 5 the transition to turbulence with the Conic nozzle around M J =0.3 was much sharper, and the difference in peak turbulence between the two cases was larger.…”

Section: Results For Conic and Asme Nozzlesmentioning

confidence: 99%

“…Relatively recently, a large number of numerical as well as a few experimental studies have been conducted on the initial BL effect as well as the effect of upstream conditions on flow and noise. [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] Most of the studies on initial BL effect were comprehensive also analyzing the flow field evolution and its stability characteristics but here we focus on the far field noise vis-à-vis the exit BL state and thickness.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Initial boundary layer state of typical model-scale jet nozzles and its impact on noise

Zaman

2023

International Journal of Aeroacoustics

View full text Add to dashboard Cite

A set of 2-inch diameter nozzles is used to investigate the effect of varying exit boundary layer (BL) states on the radiated noise from high-subsonic jets. It is confirmed that nozzles involving turbulent boundary layers are the quietest while others, involving nominally-laminar BLs, are noisier. A turbulent BL is thicker and there is simply an effect of thickness on noise. A thicker BL results in a decrease in the sound pressure spectral amplitudes due to a less vigorous growth of instability waves in the jet’s shear layer. A nominally-laminar BL, besides being thinner, may also involve significantly higher turbulence intensities, much higher than that in a turbulent BL. Such a BL state, referred to as ‘highly disturbed laminar’, results in the largest noise amplitudes especially on the high-frequency side of the spectrum. This transitional state, often encountered with model scale nozzles, involves a ‘Blasius-like’ mean velocity profile but large velocity fluctuation intensities and intermittency. The higher initial turbulence adds to the increase in high-frequency noise. The results leave little doubt that an anomaly noted with subsonic jet noise databases in the literature is due to similar effects of differences in the initial boundary layer state.

show abstract

“…These results were in agreement with experimental data presented in [12,13] where the noise emitted by tripped and un-tripped jets was investigated. Karon and Ahuja [14] found that a jet cexhausting from nozzles designed to reduce the axial velocity variation and the turbulence intensity, produces more noise compared to a nozzle with a fully developed flow at the exit. Furthermore, as speculated by Zaman [5], an increase of turbulence intensity in the initial region of the jet shear layer leads to an increase of highfrequency noise.…”

Section: Introductionmentioning

confidence: 99%

On the influence of the nozzle exhaust initial conditions on the near field acoustic pressure

2022

View full text Add to dashboard Cite

In this paper, the acoustic pressure generated in the near field of a single stream cold jet is investigated. The analysis is focused on the effect of the initial conditions at the nozzle exit parametrized by considering two different turbulence levels and two different boundary layer thicknesses. The study has been performed by processing a numerical database obtained by large-eddy simulations (LES) of a jet flow at M = 0.9 and Re = 105. Pressure time series are obtained from pointwise virtual probes located in several radial and axial positions in the jet near-field. The acoustic pressure is extracted by the application of a consolidated wavelet-based procedure and the achieved acoustic signals are analyzed in terms of global quantities as well as by computing wavelet-reconstructed Fourier spectra. The results show that both the boundary-layer thickness and the turbulence level significantly affect the acoustic pressure in terms of its intensity and directivity whereas the distribution of energy in the frequency domain depends appreciably, only on the boundary-layer thickness.

show abstract

Role of nozzle-exit boundary layer in producing jet noise

Cited by 4 publications

References 37 publications

Reynolds number and jet noise scaling

Reynolds number and jet noise scaling

Initial boundary layer state of typical model-scale jet nozzles and its impact on noise

On the influence of the nozzle exhaust initial conditions on the near field acoustic pressure

Contact Info

Product

Resources

About