Effect of Distortion on Turbofan Tonal Noise at Cutback with Hybrid Methods

Daroukh, Majd; Moreau, Stéphane; Gourdain, Nicolas; Boussuge, Jean‐François; Sensiau, Claude

doi:10.3390/ijtpp2030016

Cited by 12 publications

(12 citation statements)

References 27 publications

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“…Winkler et al considered the effect of an inlet distortion on short engine inlets [39]. But only recently Daroukh et al considered all the effects together by computing the 360 • of a typical UHBR turbofan including a short nacelle, a strong OGV heterogeneity and the IGV of the primary engine stream, both at approach [11] and cutback conditions [40]. The flow field at approach for the axisymmetric air inlet is shown by the Q-criterion (second invariant of the velocity gradient) colored by vorticity in Figure 8.…”

Section: Resultsmentioning

confidence: 99%

“…Goldstein has proposed an extension of the FWH analogy by replacing the free-field Green's function with the Green's function in an infinite cylinder in the presence of an axial uniform flow [10]. This can be further generalized by considering the Green's function in an infinite annular duct [11]. Note that the assumption of a constant axial flow does not hold in the interstage region, which is bound to play a more important role in UHBR with shorter nacelles.…”

Section: Analytical Modelsmentioning

confidence: 99%

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Turbomachinery Noise Predictions: Present and Future

Moreau

2019

Acoustics

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In future Ultra-High By-Pass Ratio turboengines, the turbomachinery noise (fan and turbine stages mainly) is expected to increase significantly. A review of analytical models and numerical methods to yield both tonal and broadband contributions of such noise sources is presented. The former rely on hybrid methods coupling gust response over very thin flat plates of finite chord length, either isolated or in cascade, and acoustic analogies in free-field and in a duct. The latter yields tonal noise with unsteady Reynolds-Averaged Navier–Stokes (u-RANS) simulations, and broadband noise with Large Eddy Simulations (LES). The analytical models are shown to provide good and fast first sound estimates at pre-design stages, and to easily separate the different noise sources. The u-RANS simulations are now able to give accurate estimates of tonal noise of the most complex asymmetric, heterogeneous fan-Outlet Guiding Vane (OGV) configurations. Wall-modeled LES on rescaled stage configurations have now been achieved on all components: a low-pressure compressor stage, a transonic high-pressure turbine stage and a fan-OGV configuration with good overall sound power level predictions for the latter. In this case, hybrid Lattice–Boltzmann/very large-eddy simulations also appear to be an excellent alternative to yield both contributions accurately at once.

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Section: Resultsmentioning

confidence: 99%

Section: Analytical Modelsmentioning

confidence: 99%

Turbomachinery Noise Predictions: Present and Future

Moreau

2019

Acoustics

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“…However, the SPL directivity was impacted by the distortion in the forward arc due to the asymmetric flow gradients at the inlet. Contrarily to that, the work done by Daroukh et al [27] shows that the emitted sound of an engine considering an asymmetric intake can significantly increase -in their case by about 3 dB compared to an equivalent setup considering an axisymmetric intake. Also, the P2T2 sensor could create a tone by the interaction of its wake with the rotor.…”

Section: Comparison Of Numerical and Experimental Far Field Datamentioning

confidence: 95%

“…To account for these uncertainties, an established practice is to aim for 40 PPW in all directions for the acoustically cut-on modes. This is conservative compared to other meshing routines used by different authors [25,26,27] in the community, who typically aim for a resolution of at least 20 to 25 PPW. Thus, the configuration studied in this work is comparatively rather well resolved.…”

Section: Mesh Generationmentioning

confidence: 99%

The Challenge of Tonal Fan Noise Prediction for an Aircraft Engine in Flight

Kissner¹,

Guérin²,

Enghardt³

et al. 2019

Acta Acustica united with Acustica

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Expensive flyover tests are needed to verify that noise certification standards are fulfilled. Currently, no numerical alternative exists to perform a holistic "virtual fly-over" test. As a step towards enabling such evaluations in the future, the authors focus on an isolated noise source-the tonal rotor-stator-interaction (RSI) of the fan stage. A high-fidelity simulation relying on a state-of-the-art yet computationally efficient method is performed for a V2527 aircraft engine in approach conditions. The computational domain includes the noise generation in the fan stage, its propagation in the engine inlet and bypass duct, as well as its radiation into the far field. Installation effects due to bifurcations and struts in the duct, ESS (engine section stator), liners, and inflow distortions are not considered. Post-processing methods are introduced and applied to the numerical data to allow for a meaningful comparison of the results to microphone data recorded during flyover experiments. In particular, great care is taken to quantify the numerical dissipation of the simulation inside the nacelle and to enable a suitable correction of the numerical data. The numerical simulation cannot fully reproduce the experimental data indicating that its level of complexity is not yet sufficient. As there is no obvious cause for the mismatch, it would be necessary to incrementally increase the complexity of the simulation in order to pinpoint the most significant sources and effects.

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“…This is typically the case during landing or take-off operations (angle of attack around 10°-15°) where airport neighbours are the most exposed to noise nuisance. Several recent studies have therefore focused on the impact of distortion on the noise emitted by turbofan engines [1][2][3][4][5][6][7][8]. They have shown that the tone noise characteristics can be significantly modified by: (a) introducing new acoustic sources caused by the distortion/fan blades interaction [3][4][5], (b) modifying the conventional fan-blade wakes/Outlet Guide Vanes (OGVs) interaction [3][4][5]8], and (c) modifying the generation and propagation of fan-blade shocks at transonic speeds [1][2][3][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Shockwave Generation and Radiation from an UHBR Engine with Flow Distortion Using a CFD/CAA Chaining Strategy

Daroukh¹,

Polacsek²,

Chelius³

2019

25th AIAA/CEAS Aeroacoustics Conference

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This paper presents aeroacoustic investigations on a full-scale Ultra High Bypass Ratio (UHBR) engine with inflow distortion at transonic conditions. Computational Fluid Dynamics (CFD) simulations are first realized to compute the shocks in the vicinity of the fan. The shocks are then radiated outside of the nacelle thanks to Computational AeroAcoustics (CAA) simulations. The same solver is used for both CFD and CAA simulations and the chaining is done by injecting the shocks in terms of usual conservative variables using a non-reflecting boundary condition. The CAA solver is based on the non-linearized Euler equations which allows to define the CFD/CAA interface close to the fan where the propagation of shocks is highly non-linear. Both shock generation and shock propagation mechanisms are investigated and the effects of inflow distortion are highlighted by comparison with a baseline case without distortion. It is shown that the distortion, characterized by an acceleration of the flow at the bottom of the nacelle, is responsible for a modification of the shock amplitudes that depends on the circumferential position. Thus, azimuthal modes appear in addition to the rotor-locked mode present without distortion. The near-field radiation is also highly impacted with most of the noise being directed towards the sky. This is due to the blockage of shocks by a supersonic flow region in the bottom of the nacelle. The radiation is in addition highly heterogeneous in the other directions because of the various angles of the shocks that leave the nacelle.

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Effect of Distortion on Turbofan Tonal Noise at Cutback with Hybrid Methods

Cited by 12 publications

References 27 publications

Turbomachinery Noise Predictions: Present and Future

Turbomachinery Noise Predictions: Present and Future

The Challenge of Tonal Fan Noise Prediction for an Aircraft Engine in Flight

Shockwave Generation and Radiation from an UHBR Engine with Flow Distortion Using a CFD/CAA Chaining Strategy

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