Experimental investigation of the turbulent density – Far-field sound correlations in compressible jets

2018 ◽  
Vol 17 (4-5) ◽  
pp. 521-540 ◽  
Author(s):  
Bertrand Mercier ◽  
Thomas Castelain ◽  
Christophe Bailly
Keyword(s):  
High Speed ◽  
Rayleigh Scattering ◽  
Photon Counting ◽  
Supersonic Jet ◽  
Density Fluctuations ◽  
Far Field ◽  
Noise Emission ◽  
Jet Mixing ◽  
Cross Correlations ◽  
Mixing Noise

Jet mixing noise is experimentally investigated by means of cross-correlations between density fluctuations inside the turbulent jet flow and the far-field acoustic pressure. The time-resolved density fluctuations are measured by an experimental device based on Rayleigh scattering, which is mounted in the large anechoic wind tunnel of Ecole Centrale de Lyon. An original signal processing developed in a previous study is implemented for the photon counting, combined with the use of a single photomultiplier to remove shot noise. A high-speed subsonic jet and a perfectly expanded supersonic jet with a subsonic convective velocity are considered to characterize mixing noise sources. In order to go beyond the classical Fourier analyses, conditional cross-correlations are determined, and the signature of turbulent events linked to the noise emission in the downstream direction is extracted.

Crackle - A dominant component of supersonic jet mixing noise

2000 ◽  
Author(s):  
A. Krothapalli ◽  
L. Venkatakrishnan ◽  
L. Lourenco
Keyword(s):  
Supersonic Jet ◽  
Jet Mixing ◽  
Dominant Component ◽  
Mixing Noise

Numerical and Experimental Studies on the Supersonic Coaxial Jet Mixing

2011 ◽  
Vol 354-355 ◽  
pp. 691-695
Author(s):  
N. Karthikeyan ◽  
B T N Sridhar
Keyword(s):  
High Speed ◽  
Cfd Simulation ◽  
Experimental Studies ◽  
Supersonic Jet ◽  
Vortex Structures ◽  
Engineering Systems ◽  
Experimental Conditions ◽  
Jet Mixing ◽  
Pressure Profiles ◽  
Mixing Characteristics

Coaxial nozzles are an integral part of many engineering systems where mixing of different fluid streams is required. Single noncircular nozzles have been shown to have better mixing characteristics than their axisymmetric counterparts. Therefore, a combination of such nozzles into coaxial configurations is promising. The aim of the present study is to quantitatively determine the effects of the geometry of the primary supersonic jet on the mixing characteristics with the secondary high speed subsonic jet. Measurements of pressure profiles at several positions along central axis of jets using identical facilities and nominally identical experimental conditions were done. The mixing is dominated by the vortex structures that are present in the inner shear layers. The interaction of the vortex structures govern the growth, and entrainment, and mixing of the jet. Also, the experimental results show that the radial and centerline pressure profiles through various coaxial jets has good correlation with the CFD simulation.

Acoustics measurements of military-style supersonic beveled nozzle jets with interior corrugations

2016 ◽  
Vol 16 (1-2) ◽  
pp. 21-43 ◽  
Author(s):  
Russell W Powers ◽  
Dennis K McLaughlin
Keyword(s):  
Noise Reduction ◽  
Acoustic Field ◽  
High Speed ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Operating Conditions ◽  
Military Aircraft ◽  
Azimuthal Dependence ◽  
Penn State ◽  
Mixing Noise

Increasingly powerful and noisy military aircraft have generated the need for research leading to the development of supersonic jet noise reduction devices. The hot, high speed supersonic jets exhausting from military aircraft during takeoff present a most challenging problem. The present study extends prior research on two methods of noise reduction. The first is the internal nozzle corrugations pioneered by Seiner et al. and the second is the beveled exit plane explored most recently by Viswanathan. A novel research idea of creating fluidic corrugations similar to the nozzle corrugations has been initiated by Penn State. To further the understanding and analysis of the fluidic corrugations, the present study focuses on the flow field and acoustic field of nozzles with two, three, and six conventional, hardwalled corrugations. The effect of the combination of the internal corrugations with a beveled nozzle is explored. The results show that significant noise reductions of over 3 dB of the mixing noise and the broadband shock-associated noise can be achieved. The combination of the beveled nozzle and the internal nozzle corrugations showed that there is less azimuthal dependence of the acoustic field than for the purely beveled nozzle. The combination nozzle was shown to reduce the noise over a wider range of polar angles and operating conditions than either the purely beveled nozzle or the purely corrugated nozzle.

Computation of supersonic jet mixing noise for an axisymmetric convergent-divergent nozzle

1994 ◽  
Vol 31 (3) ◽  
pp. 603-609 ◽  
Author(s):  
Abbas Khavaran ◽  
Eugene A. Krejsa ◽  
Chan M. Kim
Keyword(s):  
Supersonic Jet ◽  
Jet Mixing ◽  
Mixing Noise

scholarly journals The sources of jet noise: experimental evidence

2008 ◽  
Vol 615 ◽  
pp. 253-292 ◽  
Author(s):  
CHRISTOPHER K. W. TAM ◽  
K. VISWANATHAN ◽  
K. K. AHUJA ◽  
J. PANDA
Keyword(s):  
High Speed ◽  
Noise Source ◽  
Jet Noise ◽  
Polar Angle ◽  
Sound Field ◽  
Source Distribution ◽  
Far Field ◽  
Noise Sources ◽  
Directional Information ◽  
Jet Mixing

The primary objective of this investigation is to determine experimentally the sources of jet mixing noise. In the present study, four different approaches are used. It is reasonable to assume that the characteristics of the noise sources are imprinted on their radiation fields. Under this assumption, it becomes possible to analyse the characteristics of the far-field sound and then infer back to the characteristics of the sources. The first approach is to make use of the spectral and directional information measured by a single microphone in the far field. A detailed analysis of a large collection of far-field noise data has been carried out. The purpose is to identify special characteristics that can be linked directly to those of the sources. The second approach is to measure the coherence of the sound field using two microphones. The autocorrelations and cross-correlations of these measurements offer not only valuable information on the spatial structure of the noise field in the radial and polar angle directions, but also on the sources inside the jet. The third approach involves measuring the correlation between turbulence fluctuations inside a jet and the radiated noise in the far field. This is the most direct and unambiguous way of identifying the sources of jet noise. In the fourth approach, a mirror microphone is used to measure the noise source distribution along the lengths of high-speed jets. Features and trends observed in noise source strength distributions are expected to shed light on the source mechanisms. It will be shown that all four types of data indicate clearly the existence of two distinct noise sources in jets. One source of noise is the fine-scale turbulence and the other source is the large turbulence structures of the jet flow. Some of the salient features of the sound field associated with the two noise sources are reported in this paper.

Computation of jet mixing noise due to coherent structures: the plane jet case

1997 ◽  
Vol 335 ◽  
pp. 261-304 ◽  
Author(s):  
F. BASTIN ◽  
P. LAFON ◽  
S. CANDEL
Keyword(s):  
Coherent Structures ◽  
Large Scale ◽  
Supersonic Jet ◽  
Low Frequency ◽  
Coherent Motion ◽  
Mean Flow ◽  
Jet Mixing ◽  
Deterministic Modelling ◽  
Plane Jets ◽  
Mixing Noise

A computational approach to the prediction of jet mixing noise is described. It is based on Lighthill's analogy, used together with a semi-deterministic modelling of turbulence (SDM), where only the large-scale coherent motion is evaluated. The features of SDM are briefly illustrated in the case of shear layers, showing that suitable descriptions of the mean flow and of the large-scale fluctuations are obtained. Aerodynamic calculations of two cold fully expanded plane jets at Mach numbers 0.50 and 1.33 are then carried out. The numerical implementation of Lighthill's analogy is described and different integral formulations are compared for the two jets. It is shown that the one expressed in a space–time conjugate (κ, ω)-plane is particularly convenient and allows a simple geometrical interpretation of the computations. Acoustic results obtained with this formulation are compared to relevant experimental data. It is concluded that the radiation of subsonic jets cannot be explained only by the contribution of the turbulent coherent motion. In this case, directivity effects are well recovered but the acoustic spectra are too narrow and limited to the low-frequency range. In contrast at Mach number 1.33, especially in the forward quadrant, results are satisfactory, showing that coherent structures indeed provide the main source of supersonic jet mixing noise.

Experimental study on the flow and noise characteristics of underexpanded notched slot jets

2001 ◽  
Vol 105 (1047) ◽  
pp. 267-276 ◽  
Author(s):  
S. B. Verma ◽  
E. Rathakrishnan
Keyword(s):  
Major Axis ◽  
Minor Axis ◽  
Mean Flow ◽  
Noise Emission ◽  
Shock Cell ◽  
Low Velocity ◽  
Jet Mixing ◽  
Noise Characteristics ◽  
Notch Geometry ◽  
Mixing Noise

AbstractAn experimental investigation has been carried out to study the effect of notches on the flow and noise characteristics of 2:1 elliptic-slot jets. The effect of variation in notch geometry is also investigated. The presence of the notch is found to provide low-velocity regions in the notched-minor-axis plane thereby intensifying the jet growth along that plane. The interaction of these low-velocity regions with the mean flow results in shorter core-lengths. At under-expansion, the shock-cell lengths are weakened considerably in notched jets resulting in significant reductions in the overall jet noise level. Azimuthal directivity of elliptic jets indicate higher noise intensity radiated along major-axis ends relative to minor-axis sides. Notches seem to circumferentially modify the noise emission characteristics and significantly bring down the noise levels along major-axis-unnotched plane. Polar directivity indicates reduction in both shock noise and jet mixing noise in the forward quadrant.

On the Limitations of High Speed Jet Noise Suppression (Keynote Paper)

2003 ◽  
Author(s):  
Anjaneyuly Krothapalli ◽  
Brenton Greska ◽  
Vijay Arakeri
Keyword(s):  
High Speed ◽  
Noise Suppression ◽  
Jet Noise ◽  
Current Data ◽  
Wave Radiation ◽  
Far Field ◽  
Noise Sources ◽  
Turbulence Suppression ◽  
Mixing Noise ◽  
Large Eddies

This paper deals with an experimental investigation on the suppression of high-speed jet noise using air/water microjet injection at the nozzle exit. The far-field acoustic measurements from a high temperature Mj = 1.38 and Mj = 0.9 axisymmetric jet issuing from a converging nozzle show the suppression of screech tones, Mach wave radiation/crackle and mixing noise due to the use of microjets. Estimations of the contributions of different noise sources to the far-field sound are made using the current data supported by observations of previous investigators. It appears that the mixing noise reduction due to elimination of large eddies is found to be about 3–5 dB. Any further reduction of noise may only be accomplished by significant turbulence suppression and thermodynamic changes in the jet.

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