Development of a Large-Scale Microphone Array for Aircraft Jet Plume Noise Source Characterization

2011 ◽  
Author(s):  
Kurt Veggeberg ◽  
Michael James
Keyword(s):  
Large Scale ◽  
Noise Source ◽  
Microphone Array ◽  
Source Characterization

A Study of the Correlation of Large-Scale Structure Dynamics and Far-Field Radiated Noise in an Excited Mach 0.9 Jet

2009 ◽  
Vol 8 (3) ◽  
pp. 231-259 ◽  
Author(s):  
Jeff Kastner ◽  
Jin-Hwa Kim ◽  
Mo Samimy
Keyword(s):  
Large Scale ◽  
Noise Source ◽  
Microphone Array ◽  
Polar Angle ◽  
Streamwise Velocity ◽  
Source Distribution ◽  
Far Field ◽  
Potential Core ◽  
Velocity Fluctuations ◽  
Field Noise

The main goal of the present work is to excite various instabilities of an axisymmetric Mach 0.9 jet with a ReD of 0.76 × 106, track the ensuing large-scale structures/instability waves, and investigate relations between the dynamics of these structures and the far-field sound. The jet was excited over a large range of Strouhal numbers and several azimuthal modes by eight localized arc filament plasma actuators, equally spaced around the circumference of the nozzle, near the nozzle exit. The flow field and far-field noise were investigated using particle image velocimetry and a three-dimensional array of 12 microphones at 30° polar angle to the downstream jet axis. The microphone array results show that the high amplitude noise radiated to 30° polar angle is originated just downstream of the end of the potential core, in agreement with our previous results and the results in the literature. The streamwise noise source distribution was only sensitive to azimuthal modes around the jet preferred mode. Otherwise, the general trend was that forcing the jet at low Strouhal numbers moves the distribution upstream compared to the baseline jet, and at high Strouhal numbers results in a source distribution similar to the baseline jet. ***Conditionally-averaged PIV data were used to relate the flow dynamics and noise sources. The growth, saturation, and decay of the conditionally-averaged velocity fluctuations along the jet centerline correlate well with the far-field noise and the noise source distribution estimated using the microphone array. For m = 0 mode excitation around the jet column Strouhal number, the conditionally-averaged streamwise velocity fluctuations correlate well with the noise source distribution. While for m = 1, the correlation is best with the conditionally-averaged cross-stream fluctuations.

scholarly journals Instability wave models for the near-field fluctuations of turbulent jets

2011 ◽  
Vol 689 ◽  
pp. 97-128 ◽  
Author(s):  
K. Gudmundsson ◽  
Tim Colonius
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Microphone Array ◽  
Near Field ◽  
Turbulent Jets ◽  
Instability Wave ◽  
Mean Flow ◽  
Velocity Fluctuations ◽  
The Mean ◽  
Scale Structures

AbstractPrevious work has shown that aspects of the evolution of large-scale structures, particularly in forced and transitional mixing layers and jets, can be described by linear and nonlinear stability theories. However, questions persist as to the choice of the basic (steady) flow field to perturb, and the extent to which disturbances in natural (unforced), initially turbulent jets may be modelled with the theory. For unforced jets, identification is made difficult by the lack of a phase reference that would permit a portion of the signal associated with the instability wave to be isolated from other, uncorrelated fluctuations. In this paper, we investigate the extent to which pressure and velocity fluctuations in subsonic, turbulent round jets can be described aslinearperturbations to the mean flow field. The disturbances are expanded about the experimentally measured jet mean flow field, and evolved using linear parabolized stability equations (PSE) that account, in an approximate way, for the weakly non-parallel jet mean flow field. We utilize data from an extensive microphone array that measures pressure fluctuations just outside the jet shear layer to show that, up to an unknown initial disturbance spectrum, the phase, wavelength, and amplitude envelope of convecting wavepackets agree well with PSE solutions at frequencies and azimuthal wavenumbers that can be accurately measured with the array. We next apply the proper orthogonal decomposition to near-field velocity fluctuations measured with particle image velocimetry, and show that the structure of the most energetic modes is also similar to eigenfunctions from the linear theory. Importantly, the amplitudes of the modes inferred from the velocity fluctuations are in reasonable agreement with those identified from the microphone array. The results therefore suggest that, to predict, with reasonable accuracy, the evolution of the largest-scale structures that comprise the most energetic portion of the turbulent spectrum of natural jets, nonlinear effects need only be indirectly accounted for by considering perturbations to the mean turbulent flow field, while neglecting any non-zero frequency disturbance interactions.

Wavepacket noise source model for microphone array data analysis of hot supersonic jets

2013 ◽  
Vol 134 (5) ◽  
pp. 4127-4127 ◽  
Author(s):  
Philip Morris ◽  
Robert Dougherty ◽  
Chris Nelson ◽  
Alan Cain ◽  
Kenneth Brentner
Keyword(s):  
Data Analysis ◽  
Noise Source ◽  
Microphone Array ◽  
Source Model ◽  
Supersonic Jets ◽  
Array Data

scholarly journals Anisotropic source modelling for turbulent jet noise prediction

2019 ◽  
Vol 377 (2159) ◽  
pp. 20190075 ◽  
Author(s):  
Xihai Xu ◽  
Xiaodong Li
Keyword(s):  
Large Scale ◽  
Noise Source ◽  
Jet Noise ◽  
Source Model ◽  
Noise Prediction ◽  
Reynolds Stresses ◽  
Acoustic Analogy ◽  
Mean Flow ◽  
Navier Stokes Equation ◽  
Anisotropic Source

An anisotropic component of the jet noise source model for the Reynolds-averaged Navier–Stokes equation-based jet noise prediction method is proposed. The modelling is based on Goldstein's generalized acoustic analogy, and both the fine-scale and large-scale turbulent noise sources are considered. To model the anisotropic characteristics of jet noise source, the Reynolds stress tensor is used in place of the turbulent kinetic energy. The Launder–Reece–Rodi model (LRR), combined with Menter's ω -equation for the length scale, with modified coefficients developed by the present authors, is used to calculate the mean flow velocities and Reynolds stresses accurately. Comparison between predicted results and acoustic data has been carried out to verify the accuracy of the new anisotropic source model. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.

Open-source software for the application of microphone array methods

2017 ◽  
Vol 48 (3-4) ◽  
pp. 44-51 ◽  
Author(s):  
Gert Herold ◽  
Ennes Sarradj
Keyword(s):  
Open Source ◽  
Open Source Software ◽  
Time Domain ◽  
Microphone Array ◽  
Synthetic Data ◽  
Object Oriented ◽  
Source Characterization ◽  
Acoustic Source ◽  
Array Data ◽  
Flexible Programming

The open-source Python library Acoular is aimed at the processing of microphone array data. It features a number of algorithms for acoustic source characterization in time domain and frequency domain. The modular, object-oriented architecture allows for flexible programming and a multitude of applications. This includes the processing of measured array data, the mapping of sources, the filtering of subcomponent noise, and the generation of synthetic data for test purposes. Several examples illustrating its versatility are given, as well as one example for implementing a new algorithm into the package.

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