A Two-Microphone Method For The Estimation Of The Mode Amplitude Distribution on Multimode Broadband Sound Field in Finie-Length Ducts With Uniform Mean Flow

2014 ◽  
Author(s):  
Phillip Joseph ◽  
Fabien Mouries ◽  
Lars Enghardt
Keyword(s):  
Sound Field ◽  
Amplitude Distribution ◽  
Mean Flow ◽  
Mode Amplitude ◽  
Broadband Sound

scholarly journals Construction and Analysis of an Adapted Spectral Finite Element Method to Convective Acoustic Equations

2016 ◽  
Vol 20 (1) ◽  
pp. 1-22 ◽  
Author(s):  
Andreas Hüppe ◽  
Gary Cohen ◽  
Sébastien Imperiale ◽  
Manfred Kaltenbacher
Keyword(s):  
Finite Element ◽  
Sound Field ◽  
Mean Flow ◽  
Fe Method ◽  
Spurious Solutions ◽  
Acoustic Equations ◽  
The Mean ◽  
Spectral Finite Element Method ◽  
Flow Effects ◽  
Spectral Finite Element

AbstractThe paper addresses the construction of a non spurious mixed spectral finite element (FE) method to problems in the field of computational aeroacoustics. Based on a computational scheme for the conservation equations of linear acoustics, the extension towards convected wave propagation is investigated. In aeroacoustic applications, the mean flow effects can have a significant impact on the generated sound field even for smaller Mach numbers. For those convective terms, the initial spectral FE discretization leads to non-physical, spurious solutions. Therefore, a regularization procedure is proposed and qualitatively investigated by means of discrete eigenvalues analysis of the discrete operator in space. A study of convergence and an application of the proposed scheme to simulate the flow induced sound generation in the process of human phonation underlines stability and validity.

Aerodynamic sound generation in a pipe

1968 ◽  
Vol 32 (4) ◽  
pp. 765-778 ◽  
Author(s):  
H. G. Davies ◽  
J. E. Ffowcs Williams
Keyword(s):  
Acoustic Waves ◽  
Large Scale ◽  
Sound Field ◽  
Convective Motion ◽  
Energy Output ◽  
Small Scale ◽  
Mean Flow ◽  
Limited Region ◽  
Aerodynamic Sound ◽  
Scale Turbulence

The paper deals with the problem of estimating the sound field generated by a limited region of turbulence in an infinitely long, straight, hard-walled pipe. The field is analysed in a co-ordinate system moving with the assumed uniform mean flow, and the possibility of eddy convection relative to that reference system is considered. Large-scale turbulence is shown to induce plane acoustic waves of intensity proportional to the sixth power of flow velocity. The same is true of small-scale turbulence of low characteristic frequency. In both cases convective effects increase the acoustic output and distribute the bulk of the energy in a mode propagating upstream against the mean flow. Small-scale turbulence of higher frequency excites more modes, the sound increasing with very nearly the eighth power of velocity (U7.7) as soon as the second mode is excited. In the limit, when more than about 20 modes are excited, the energy output is unaffected by the constraint of the pipe walls, increasing with the eighth power of velocity, and being substantially amplified by convective motion.

The Effect of Sound on Vortex Shedding From Single and Tandem Cylinders

2002 ◽  
Author(s):  
Joseph W. Hall ◽  
Samir Ziada ◽  
David S. Weaver
Keyword(s):  
Vortex Shedding ◽  
Sound Field ◽  
Open Circuit ◽  
Mean Flow ◽  
Number Range ◽  
Single Cylinder ◽  
Tandem Cylinders ◽  
Vortex Shedding Frequency ◽  
The Mean ◽  
Lock In

A single cylinder and two tandem cylinders configurations with longitudinal pitch ratios L/D = 1.75 and 2.5 were rigidly mounted in an open circuit windtunnel and a sound field was applied so that the acoustic particle velocity was normal to both the cylinder axis and the mean flow velocity. Tests were performed for a Reynolds number range of 5000 < ReD < 24000. The effect of sound on the vortex shedding was investigated by instrumenting the cylinders with pressure taps and hot-wire probes. These tests show that applied sound can entrain and shift the natural vortex shedding frequency to the frequency of excitation and produce nonlinearities in the wake. The lock-in envelope for the tandem cylinders is considerably larger than for the single cylinder. The lock-in range for the smaller tandem cylinder spacing (L/D = 1.75) was broader still than either the single cylinder, or the L/D = 2.5 tandem cylinder case.

Direct Calculation of Sound Radiated From Bodies in Nonuniform Flows

1993 ◽  
Vol 115 (4) ◽  
pp. 573-579 ◽  
Author(s):  
H. M. Atassi ◽  
J. Fang ◽  
S. Patrick
Keyword(s):  
Acoustic Pressure ◽  
Three Dimensional ◽  
Sound Field ◽  
Direct Calculation ◽  
Significant Rise ◽  
Mean Flow ◽  
Unsteady Pressure ◽  
Potential Part ◽  
The Mean ◽  
Radiated Sound

Sound radiated from a single airfoil and a cascade of airfoils in three-dimensional gusts is directly calculated. Euler’s equations are linearized about the mean flow of the airfoil or cascade. The velocity field is split into a vortical part and a potential part. The latter is governed by a single nonconstant-coefficient convective wave equation. For a single airfoil, the radiated sound is calculated using Kirchhoff’s method from the mid field of the unsteady pressure obtained through the unsteady aerodynamic solver. The results indicate the importance of the contribution of the quadrupole effects to the sound field. For a cascade of airfoils, the acoustic pressure is directly obtained by solving the partial differential equation. The results show that, as the maximum Mach number on the blade surface nears unity, there is a significant rise in the local unsteady pressure, and also a significant increase in the upstream acoustic pressure.

Understanding Roughness Noise: Progress in Analytical Modeling and Testing, Part 1—Shear Rapid Distortion Theory

2008 ◽  
Author(s):  
R. Martinez ◽  
J. S. Uhlman ◽  
C. M. Ting ◽  
B. S. Paul ◽  
J. M. Anderson ◽  
...  
Keyword(s):  
Broadband Noise ◽  
Operating Conditions ◽  
Recent Experimental Data ◽  
Mean Flow ◽  
Rapid Distortion Theory ◽  
Roughness Elements ◽  
Scaling Parameters ◽  
Layer Flow ◽  
Broadband Sound

This is the first of a two-part paper that lays out a theory of broadband noise from rough surfaces and uses it to interpret recent experimental data. The analysis in Part 1 is based on an application of Rapid Distortion Theory to an incident field of correlated micro-velocities defined upstream of the roughened region. Those velocity disturbances are linked to the frequency-wavenumber spectrum of wall pressures from a standard model of turbulent boundary-layer flow. The field of incident microvelocities distorts as it is convected irregularly around and over the roughness elements and thereby generates the predicted broadband sound. Computed results in the Part-2 paper will gauge the role of a boundary layer’s mean shear in the noise-production process relative to the rapid distortions carried by an artificially irrotational mean flow (for reasons to be described in Part 2, shear effects turn out to be insignificant for the application of immediate interest). Calculations in support of recent measurements will be presented for a range of operating conditions and for their associated set of dimensionless scaling parameters.

The influence of jet flow on jet noise. Part 1. The noise of unheated jets

1976 ◽  
Vol 73 (4) ◽  
pp. 753-778 ◽  
Author(s):  
R. Mani
Keyword(s):  
Plug Flow ◽  
Jet Noise ◽  
Sound Field ◽  
Point Of View ◽  
Noise Generation ◽  
Acoustic Analogy ◽  
Mean Flow ◽  
Supersonic Regime ◽  
Noise Data ◽  
Jet Velocity

The present paper and part 2 (adjacent) study the sound field produced by a convected point quadrupole embedded in and moving along the axis of a round plug-flow jet. Only subsonic eddy convection velocities are considered. We examine cold jets here and hot jets in part 2. A principal feature of the study is extensive comparison with jet-noise data. It appears that this simple model problem succeeds in explaining all the major interesting features of jet-noise data, on both hot and cold jets, for jet exit velocities in the low supersonic range. Particular success is achieved in explaining aspects of the data not explainable by the Lighthill acoustic-analogy approach. The picture of jet-noise generation that emerges (at least for jet velocities in the low supersonic regime) is in many respects a striking reaffirmation of the Lighthill point of view. It appears that there is an intrinsic or universal distribution of compact quadrupoles, whose strength and frequency distribution scale with the jet velocity and nozzle diameter as would be expected from simple dimensional reasoning, responsible for jet-noise generation. These quadrupoles are of course convected by the mean flow and satisfactory agreement with the data is obtained by assuming that they are devoid of any intrinsic directionality. There appears to be no significant jet Mach number (compressibility) or jet temperature effect on the scaling of this intrinsic distribution. The essential improvement over the Lighthill analysis is the incorporation of mean-flow shrouding effects on the radiation of the convected quadrupoles. It is perhaps no exaggeration to claim that, with the incorporation of such a shrouding effect, the problem of scaling jet noise with regard to the jet velocity, jet temperature, jet size and the angle from the jet axis appears to be completely resolved. (The ‘scaling’ principle cannot of course be very simply expressed and in fact needs calculations of the sort contained in the present paper to implement it.)

scholarly journals 123 Effect of Mean Flow on Sound Field in a Curved Duct with Splitter

2000 ◽  
Vol 2000.49 (0) ◽  
pp. 45-46
Author(s):  
Ryosuke MORI ◽  
Yasuji TSUBAKISHITA
Keyword(s):  
Sound Field ◽  
Mean Flow ◽  
Curved Duct

Radial Mode Analysis of Broadband Noise in Flow Ducts Using Azimuthal Sensor Array

2017 ◽  
Author(s):  
Kunbo Xu ◽  
Weiyang Qiao ◽  
Fan Tong ◽  
Renke Wei
Keyword(s):  
Sensor Arrays ◽  
Sound Field ◽  
Broadband Noise ◽  
Power Measurement ◽  
Mode Analysis ◽  
Sound Power ◽  
Sound Waves ◽  
Axial Fan ◽  
Circular Duct ◽  
Broadband Sound

For the evaluation and improvement of fan noise reduction notions and the verification of broadband sound power measurement in flow ducts, special interest was given to the analysis of the broadband noise fields in duct. Two axial sensor arrays were wall-flush mounted upstream of a single-stage axial fan in the circular duct section of the fan inlet, staggered by 180° in the circumferential direction. During the tests, the rotating drum was rotated by step of 6 degrees to give a total 840 measurement points. There are two static reference microphones mounted upstream of rotating measurement section. Time-series of 12 seconds duration were recorded at each of the 30 azimuthal positions of the rotating duct in order to allow for a statistically accurate cross-correlation data analysis. This method is able to discriminate the sound waves propagating in upstream and downstream directions. Special attention was given to the blade passing frequencies of the axial fan. Rotor-stator interaction mode dominates the incident sound field, while modes with low azimuthal order play an important role in the reflected sound field. The reflected broadband sound power is almost 10dB lower than the transmitted sound field in a broad-frequency range. On the whole, this method behaves robustly in decomposition of broadband noise in flow duct and delivers physically meaningful broadband mode amplitudes.

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