Spectral Broadening of Jet Engine Turbine Tones

Ewert, Roland; Kornow, Oliver; Powles, Christopher; Tester, Brian J.; Delfs, Jan; Rose, Marco

doi:10.2514/6.2008-2940

Cited by 21 publications

(29 citation statements)

References 6 publications

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“…It builds upon the models proposed by Careta et al [10] and Ewert et al [14,15] where the velocity field is defined in terms of a stream function that is obtained by filtering random data. The method requires as input several statistical properties of the turbulent flow such as the energy spectrum or velocity correlation, integral length and time scales.…”

Section: Random Particle Methodsmentioning

confidence: 99%

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Random particle methods applied to broadband fan interaction noise

Dieste

Gabard

2012

Journal of Computational Physics

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Predicting broadband fan noise is key to reduce noise emissions from aircraft and wind turbines. Complete CFD simulations of broadband fan noise generation remain too expensive to be used routinely for engineering design. A more efficient approach consists in synthesizing a turbulent velocity field that captures the main features of the exact solution. This synthetic turbulence is then used in a noise source model. This paper concentrates on predicting broadband fan noise interaction (also called leading edge noise) and demonstrates that a Random Particle Mesh method (RPM) is well suited for simulating this source mechanism. The linearized Euler equations are used to describe sound generation and propagation. In this work, the definition of the filter kernel is generalized to include non-Gaussian filters that can directly follow more realistic energy spectra such as the ones developed by Liepmann and von Kármán. The velocity correlation and energy spectrum of the turbulence are found to be well captured by the RPM. The acoustic predictions are successfully validated against Amiet's analytical solution for a flat plate in a turbulent stream. A standard Langevin equation is used to model temporal decorrelation, but the presence of numerical issues leads to the introduction and validation of a second-order Langevin model.

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Section: Random Particle Methodsmentioning

confidence: 99%

“…The method used in this work is a variant of the random particle method, following the ideas developed by Careta et al [10] and Ewert et al [14,15]. In the present work we will concentrate on several aspects.…”

Section: Introductionmentioning

confidence: 99%

Random particle methods applied to broadband fan interaction noise

Dieste

Gabard

2012

Journal of Computational Physics

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“…This hypothesis is true for the vortex flow defined in Eq.(1). The second assumption introduced by Ewert et al 13 is that the scattering of the incident acoustic field is mainly induced by the unsteady velocity fluctuations. Thus the effects of the unsteady density and pressure fluctuations are negligible.…”

Section: Iia Description Of the Configuration Studiedmentioning

confidence: 99%

“…10,11,14 In order to capture the interaction between the incident acoustic field and the convected vortex, the equations solved have to contain terms involving products between the acoustic fluctuations and the vortex flow. A set of equations has been developed by Ewert et al 13 by considering small perturbations (ρ , u , p )…”

Section: Iia Description Of the Configuration Studiedmentioning

confidence: 99%

“…This model is able to consider frozen or evolving turbulence, and the variations of the source/flow parameters show behaviors of the spectra agreeing with existing experimental results. Ewert et al 12,13 perfomed first attempts of numerical calculations for such configurations solving the linearized Euler equations (LEE) in the time domain with a finite difference solver and using the stochastic RPM method in order to synthesize and introduce the turbulence in the numerical domain. The method showed promising results in its ability to recover features of the spectral broadening and its evolution with several parameters of the source or the flow.…”

Section: Introductionmentioning

confidence: 99%

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Numerical assessment of the scattering of acoustic waves by turbulent structures

Clair

Gabard

2015

21st AIAA/CEAS Aeroacoustics Conference

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The scattering of harmonic sound waves by a single vortex is studied to provide some insight into the more complex problem of sound scattering by a turbulent layer. Two different methods are used to model the scattering by a steady vortex or by a vortex convected in a uniform mean flow. The first method is based on the linearized Euler equations in the frequency domain and is used to study the scattering by a steady vortex. The speed of this method allows to perform a study of the spatial scattering of a plane wave over a wide range of frequencies, where analytical models previously developed are restricted either to low or high frequencies. The second method uses a finite difference solver, also based on the linearized Euler equations but in the time domain. This method is used to study the scattering by a vortex convected in a uniform mean fow, where a spectral scattering occurs in addition to the spatial scattering. A parametric study is realized, focusing on four parameters including the source frequency and the convection velocity. The spectra deduced from this study show a pattern similar to the haystacking observed in existing studies of the scattering by a turbulent shear layer. Some of the trends deduced from the parametric study are also in agreement with these previous observations. Thus, the detailled study of the scattering by a single eddy is able to provide further understanding of the turbulence scattering.

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