Jet Noise Turbulence Measurements

Harper-Bourne, Marcus

doi:10.2514/6.2003-3214

Cited by 78 publications

(69 citation statements)

References 13 publications

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“…The rate of decay in the peak value of the measured spatial correlations with increasing downstream separation was used to deduce a turbulent eddy convection velocity, which was found not to be equal to the local mean velocity, but rather ~0.6 times the jet velocity and varying slightly over the maximum shear region -this concept has been used in many acoustic source models ever since. It was also noted that this factor varied if the spectral content of turbulence was considered; length scales associated within different frequency bands were observed to travel at different speeds, an observation later confirmed by Harper-Bourne (2003), and made use of in the recently proposed modification to the Lighthill acoustic analogy of Self (2004). The most comprehensive early HWA investigation into 2-point quantities was that of Bradshaw et al (1964).…”

Section: Introductionmentioning

confidence: 96%

“…The paper also contains the statement that "measurement of the fluctuating stress tensor, which is the forcing term in Lighthill's equation for noise emissions, seems out of the question". In spite of this statement (although 40 years later) Harper-Bourne (2003) and Morris and Zaman (2010) were successful in extending the HWA technique to measurements of both 2 nd -and 4 th -order correlations in round jets and providing a data set that included streamwise, radial, and circumferential separations, although only for the streamwise velocity component. Morris and Zaman (2010) described how various definitions may be used to describe the 4 th -order 2-point 2-time correlation functions and their corresponding correlation coefficients.…”

Section: Introductionmentioning

confidence: 99%

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Stereo-PIV measurements of spatio-temporal turbulence correlations in an axisymmetric jet

Pokora

McGuirk

2015

J. Fluid Mech.

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Stereoscopic three-component particle image velocimetry (3C-PIV) measurements have been made in a turbulent round jet to investigate the spatio-temporal correlations that are the origin of aerodynamic noise. Restricting attention to subsonic, isothermal jets, measurements were taken in a water flow experiment where, for the same Reynolds number and nozzle size, the shortest time scale of the dynamically important turbulent structures is more than an order of magnitude greater that in equivalent airflow experiments, greatly facilitating time-resolved PIV measurements. Results obtained (for a jet nozzle diameter and velocity of 40 mm and $1~\text{m}~\text{s}^{-1}$, giving $\mathit{Re}=4\times 10^{4}$) show that, on the basis of both single-point statistics and two-point quantities (correlation functions, integral length scales) the present incompressible flow data are in excellent agreement with published compressible, subsonic airflow measurements. The 3C-PIV data are first compared to higher-spatial-resolution 2C-PIV data and observed to be in good agreement, although some deterioration in quality for higher-order correlations caused by high-frequency noise in the 3C-PIV data is noted. A filter method to correct for this is proposed, based on proper orthogonal decomposition (POD) of the 3C-PIV data. The corrected data are then used to construct correlation maps at the second- and fourth-order level for all velocity components. The present data are in accordance with existing hot-wire measurements, but provide significantly more detailed information on correlation components than has previously been available. The measured relative magnitudes of various components of the two-point fourth-order turbulence correlation coefficient ($R_{ij,kl}$) – the fundamental building block for free shear flow aerodynamic noise sources – are presented and represent a valuable source of validation data for acoustic source modelling. The relationship between fourth-order and second-order velocity correlations is also examined, based on an assumption of a quasi-Gaussian nearly normal p.d.f. for the velocity fluctuations. The present results indicate that this approximation shows reasonable agreement for the measured relative magnitudes of several correlation components; however, areas of discrepancy are identified, indicating the need for work on alternative models such as the shell turbulence concept of Afsar (Eur. J. Mech. (B/Fluids), vol. 31, 2012, pp. 129–139).

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Stereo-PIV measurements of spatio-temporal turbulence correlations in an axisymmetric jet

Pokora

McGuirk

2015

J. Fluid Mech.

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“…In Figure 11(a) both simulations have a slightly lower peak value at η = 0.2D j than that of Pokora et al However, this is reduced by η = 0.4D j . Figure 11 The relative amplitude of the second order correlations at x/D j = 4.0 is compared to the experimental results of Harper-Bourne, 7 Pokora's water tunnel data 17 and Pokora el al. 's simulation in Table 1.…”

Section: B Correlation Resultsmentioning

confidence: 98%

Large Eddy Simulation of High Reynolds Number Jets with Microjet Injection

Rife

2011

17th AIAA/CEAS Aeroacoustics Conference (32nd AIAA Aeroacoustics Conference)

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“…From the early work of Abramovich 3 passing by Towsend, 4 Lilley, 5 and Lau & Tester, 6 among many others, have found that hot-wire Particle Image Velocimetry (PIV) and modern Laser Doppler (LD) applications have an important role in turbulent jet measurements, including the case of jet noise. Measurements made in a low speed air jet (Mach = 0.18) with associated cross-spectra and spectral length scales of the axial and lateral velocity components were performed by Harper-Bourne 7 and enhanced by Morris and Zaman, 8 thus providing a more complete picture of the relevant turbulent statistics, including a wider range of reference points in the jet through cross spectra and cross correlations, second and fourth order statistics, and comparisons with a RANS prediction method. Non-intrusive techniques have been employed by Mielke et al 9 to measure velocity, density, temperature, and turbulence velocity fluctuations in sparsely seeded, high-speed gas flows, used to make measurements in a 25.4 mm diameter free jet at subsonic and supersonic flow conditions.…”

Section: According Tomentioning

confidence: 99%

Aerodynamics and Aeroacoustics Investigation of a Low Speed Subsonic Jet

Souza¹,

Proenca²,

Almeida³

et al. 2017

IJAV

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Low and high speed subsonic jets have been studied in the last 50 years mainly due to their many applications in industry, such as the discharge of turbojets and turbofan engines. The purpose of this work is to investigate the aerodynamics and the acoustical noise generated by a single stream jet flow operating at low Mach number 0.25 and Reynolds number of 2.1 × 10 5 . The main focus is the flow and acoustical characterization of this low speed jet by applying different experimental techniques for evaluating the velocity field by using measurements with a Pitot tube, hot-wire anemometry, and farfield noise acquisition by free field microphones. In order to verify the validity of aeroacoustic predictions for such a low speed jet, a Computational Fluid Dynamics by means of RANS simulations via k-ω SST model have been employed coupled with a statistically low-cost Lighthill-Ray-Tracing method in order to numerically predict the acoustic noise spectrum. The sound pressure level as a function of frequency is contructed from the experiments and compared with the noise calculations from the acoustic modeling. The numerical results for the acoustics and flow fields were well compared with the experimental data, thus showing that this low-cost flow-acoustic methodology can be used to predict the acoustic noise of subsonic jet flows, even at low speeds. R Observer's radius [m] NOMENCLATURE

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Jet Noise Turbulence Measurements

Cited by 78 publications

References 13 publications

Stereo-PIV measurements of spatio-temporal turbulence correlations in an axisymmetric jet

Stereo-PIV measurements of spatio-temporal turbulence correlations in an axisymmetric jet

Large Eddy Simulation of High Reynolds Number Jets with Microjet Injection

Aerodynamics and Aeroacoustics Investigation of a Low Speed Subsonic Jet

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