Control of the vorticity mode in the linearized Euler equations for hybrid aeroacoustic prediction

Prax, Christian; Golanski, F.; Nadal, L.

doi:10.1016/j.jcp.2008.02.022

Cited by 11 publications

(7 citation statements)

References 26 publications

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“…While Deneuve et al have access to the instantaneous velocity field during the direct-time step, only the mean flow is measured in our experiment. It is nevertheless possible to account for the interaction of sound and mean flow by solving the linearized Euler equations (LEE) 23,24 instead of the full Euler equations. It is important to stress here that this approach makes possible the introduction of a base mean flow, obtained experimentally, upon which the Euler equations are linearized.…”

Section: Introductionmentioning

confidence: 99%

Experimental localization of an acoustic sound source in a wind-tunnel flow by using a numerical time-reversal technique

Padois

Prax

Valeau

et al. 2012

The Journal of the Acoustical Society of America

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The possibility of using the time-reversal technique to localize acoustic sources in a wind-tunnel flow is investigated. While the technique is widespread, it has scarcely been used in aeroacoustics up to now. The proposed method consists of two steps: in a first experimental step, the acoustic pressure fluctuations are recorded over a linear array of microphones; in a second numerical step, the experimental data are time-reversed and used as input data for a numerical code solving the linearized Euler equations. The simulation achieves the back-propagation of the waves from the array to the source and takes into account the effect of the mean flow on sound propagation. The ability of the method to localize a sound source in a typical wind-tunnel flow is first demonstrated using simulated data. A generic experiment is then set up in an anechoic wind tunnel to validate the proposed method with a flow at Mach number 0.11. Monopolar sources are first considered that are either monochromatic or have a narrow or wide-band frequency content. The source position estimation is well-achieved with an error inferior to the wavelength. An application to a dipolar sound source shows that this type of source is also very satisfactorily characterized.

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Section: Introductionmentioning

confidence: 99%

Experimental localization of an acoustic sound source in a wind-tunnel flow by using a numerical time-reversal technique

Padois

Prax

Valeau

et al. 2012

The Journal of the Acoustical Society of America

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“…To avoid the numerical singularity at the center of the vortices, the vortex core model 20 is used, and the other method involves placing the mesh points far enough from the vortex centers. 22 The original point vortex, Rankine vortex and Scully vortex tangential velocity variation against the radial distance are plotted in Fig. 4.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the SEM has been widely used in wave propagation studies, 15,16 CFD 17 and CAA. [18][19][20] The motivation for simulating the sound generated by a corotating vortex pair 5,[21][22][23] in this work is that various vortices occupy only a very small portion in a flow but play a key role in organizing the flow, 24 as "the sinews and muscles of the fluid motion" 25 and "the sinews of turbulence". 26 Vortices are also "the voice of fluid motion" 27 because they, at low Mach numbers, are the only source of aeroacoustic sound and noise.…”

Section: Introductionmentioning

confidence: 99%

Application of Spectral Element Method Combining Dilatation Theory to Sound Generated by a Co-rotating Vortex Pair

Bao¹,

Qin²

2018

IJAV

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A spectral element method for the simulation of an acoustic field is applied to the case of a co-rotating vortex pair in both stationary medium and mean flow. Based on the dilatation theory, the second time derivative of the pseudopressure is used as the source of the inhomogeneous convected wave equation which is discretized by a spectral element method in space and the Newmark-β method in time marching. In addition, the nonreflecting boundary condition is adopted too. Then we compared the numerical results with the analytical solution. Numerical results are in good agreement with the analytical solution. Moreover, different grid spacings and time steps are investigated for evaluating the numerical accuracy. To study the frequency content of the sound, spectral analysis is also carried out. Finally, sound propagation in uniform flows and sheared mean flows are simulated and analyzed. This study shows the capabilities of the spectral element method combined with dilatation theory for the aeroacoustic problems.

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“…In the present study these input data are generated numerically. The two-dimensional simulation of acoustic waves propagation is performed through the resolution of the Linearized Euler Equations (LEE) in the space-time domain [20,21,10].…”

Section: Numerical Data Generationmentioning

confidence: 99%

Array processing for the localisation of noise sources in hot flows

Rakotoarisoa

Marx

Prax

et al. 2019

Mechanical Systems and Signal Processing

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This paper investigates the problem of localizing a sound source in a heated flow using a microphone array. Applications are found in studies dealing with the identification of sound sources in hot turbulent jets, or with the sound radiation from installed turbofans. Two configurations have been investigated: a shear layer flow (wind-tunnel type) and a jet flow. In the present study acoustic data are generated using a simulation based on the Linearized Euler Equations. For heated flows, refraction by temperature gradients is superimposed with refraction by velocity gradients, and the objective of this study is to assess whether this effect is important and how it can be accounted for in different source localisation methods. For this purpose, a time-reversal-based imaging method has been compared with a beamforming-based method in which the time-delays are computed based on ray tracing. For the shear flow, the results show that for high subsonic Mach numbers and steep thermal gradients, the thermal stratification must be taken into account to ensure a satisfactory precision of localisation for both methods. However, including the gradients of velocity and temperature is less crucial for imaging sound sources in the jet flow. The results indicate also that the localisation error is lower with the beamforming and ray-tracing technique than with the time-reversal technique, the latter being more sensitive to the limited array aperture.

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Control of the vorticity mode in the linearized Euler equations for hybrid aeroacoustic prediction

Cited by 11 publications

References 26 publications

Experimental localization of an acoustic sound source in a wind-tunnel flow by using a numerical time-reversal technique

Experimental localization of an acoustic sound source in a wind-tunnel flow by using a numerical time-reversal technique

Application of Spectral Element Method Combining Dilatation Theory to Sound Generated by a Co-rotating Vortex Pair

Array processing for the localisation of noise sources in hot flows

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