Broadband Turbomachinery Noise: Exhaust Noise Computations with Actran/TM and Actran/DGM

Manera, Julien; Leneveu, Romain; Mardjono, Jacky; Caro, Stéphane

doi:10.2514/6.2009-3292

Cited by 12 publications

(3 citation statements)

References 7 publications

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“…An alternative was proposed by Manera et al 20 For the continuity of displacement, ξ, across the vortex sheet, the displacement is related to the normal gradient of the velocity potential by way of the kinematic condition (6). Following the substitution of (6) into (8), the formulation on the vortex sheet is obtained:…”

Section: A Existing Formulations Of the Vortex Sheetmentioning

confidence: 99%

Implementation of a Vortex Sheet in a Finite Element Model Based on Potential Theory for Exhaust Noise Predictions

Prinn

Gabard

Bériot

2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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Predicting sound propagation through the jet exhaust of an aero-engine presents the specific difficulty of representing the refraction effect of the mean flow shear. This is described by the linearised Euler equations, but this model remains rather expensive to solve numerically. The other model commonly used in industry, the linearised potential theory, is faster to solve but needs to be modified to represent a shear layer. This paper presents a way to describe a vortex sheet in a finite element model based on the linearised potential theory. The key issues to address are the continuity of pressure and displacement that have to be enforced across the vortex sheet, as well as the implementation of the Kutta condition at the nozzle lip. Validation results are presented by comparison with analytical results. It is shown that the discretization of the continuity conditions is crucial to obtain a robust and accurate numerical model.

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Section: A Existing Formulations Of the Vortex Sheetmentioning

confidence: 99%

Implementation of a Vortex Sheet in a Finite Element Model Based on Potential Theory for Exhaust Noise Predictions

Prinn

Gabard

Bériot

2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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“…The simplest method to obtain uncorrelated modes is to perform one simulation per mode and sum the quadratic pressure value of each individual computation. 15 Obviously, this kind of approach is realistic only if very few modes are considered.…”

Section: Iiic Mode Coherence Cancelingmentioning

confidence: 99%

Prediction of BPF tones emitted by the inlet of an aero-engine model using in-duct angular mode spectrum measurements

Reboul

Polacsek

Billonnet

et al. 2014

20th AIAA/CEAS Aeroacoustics Conference

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The goal of this study was to realize predictions of tonal noise generated by a SNECMA turbofan mock up with a heterogeneous stator and radiated from the inlet using as input a modal decomposition made in the inlet duct wall. A numerical approach based on the CAA (Computational AeroAcoustics) code sAbrinA.V0 with an equivalent source term recently implemented is used as well as an analytical methodology using a Wiener-Hopf technique and an uniform flow assumption. Even if directivities from raw experimental data exhibit significant variations of noise level in the azimuthal direction proving that correlation effect between modes seems to be not negligible for tonal noise, the hypothesis of incoherent modes inducing axisymmetric directivities allow to compare reasonably well with measured data averaged azimuthally. Comparisons between theoretical and numerical predictions confirm the practical interest of using simplified analytical methods even if clear improvement are provided by more complex and time consuming methods like CAA. Especially, for polar angles between 20 • and 70 • , a very good agreement is obtained with a maximum discrepancy of 0.7 dB on overall sound pressure level for the three first tones.

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“…It is based on an acoustic velocity potential and is difficult to apply when the mean flow is rotational. This makes it unsuited to deal easily with turbofan exhaust noise [8] [9] although a modification of the method based on Möhring's formulation has recently been developed and shown to give promising results. The FE/IE approach also requires a direct solver for robust application, and memory usage increases very rapidly with problem size even when efficient out-of-core solvers are used.…”

Section: Introductionmentioning

confidence: 99%

Integrating CFD source predictions with time-domain CAA for intake fan noise prediction

Rarata

Gabard

Sugimoto

et al. 2014

20th AIAA/CEAS Aeroacoustics Conference

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A method is proposed for integrating a source prediction obtained from a Computational Fluid Dynamics (CFD) model for the fan stage of a turbofan engine with a Computational Aero-Acoustics (CAA) propagation code to predict tonal noise radiation in the far field. The Reynolds-Averaged Navier-Stokes equations are used to model the generation of the tones. Their propagation through the intake is simulated by applying the Discontinuous Galerkin Method to solve the linearized Euler equations in the time domain. The CFD and the CAA solutions are matched in a region where both solutions overlap and where non-linear effects, important close to the fan, can be considered to be less significant. An equivalent modal source on a notional source plane behind the fan is used to duplicate the sound field in this matching region and is then to drive a fully three-dimensional CAA radiation model for a near-field acoustic solution. The far-field sound pressure is obtained by applying the Ffowcs Williams-Hawkings formulation on a porous surface within the CAA domain. The accuracy and efficiency of this approach are investigated and results obtained are compared to measured data from a fan rig.

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Broadband Turbomachinery Noise: Exhaust Noise Computations with Actran/TM and Actran/DGM

Cited by 12 publications

References 7 publications

Implementation of a Vortex Sheet in a Finite Element Model Based on Potential Theory for Exhaust Noise Predictions

Implementation of a Vortex Sheet in a Finite Element Model Based on Potential Theory for Exhaust Noise Predictions

Prediction of BPF tones emitted by the inlet of an aero-engine model using in-duct angular mode spectrum measurements

Integrating CFD source predictions with time-domain CAA for intake fan noise prediction

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