Direct noise predictions of fan broadband noise using LES and analytical models

Al-Am, Jean; Clair, Vincent; Giauque, Alexis; Boudet, Jérôme; Aguilera, Fernando Gea

doi:10.2514/6.2022-2882

Cited by 8 publications

(6 citation statements)

References 37 publications

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“…For fully compressible LES, the acoustic power can also be directly computed upstream and downstream of the fan stage. Good agreement was obtained between direct noise predictions from a periodic fan/OGV stage and analytical models [12]. To further reduce the computation cost, some studies use simplified configurations of the periodic sector, such as linear cascades [21] or radial slices [22].…”

Section: Introductionmentioning

confidence: 85%

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Direct noise predictions of a 360° full fan stage using LES

Al-Am

Clair

Giauque

et al. 2023

AIAA AVIATION 2023 Forum

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In the present study, the broadband noise of an ultra high bypass ratio fan/OGV stage, developed at École Centrale de Lyon, is studied numerically. Wall-modeled large eddy simulations (LES) over a 360°full fan stage are performed for the first time, at approach conditions. The noise emissions in the fan stage are directly obtained by the fully compressible LES, using a well refined unstructured grid. Additionally, a LES over a periodic sector of the fan stage is performed using the same configuration and numerical setup as for the 360°LES. The results of the 360°and the periodic sector configurations are compared in terms of mean and turbulent flow parameters and acoustic pressure spectra. The impact of the periodic boundary conditions, usually used for high-fidelity simulations of turbofan engines, is thus assessed. A slightly lower pressure difference between the pressure and suction sides of the blade is obtained in the 360°LES in the blade tip region. The acoustic azimuthal decomposition, which can only be estimated using the 360°LES configuration, is presented. The evolution of the coherence function in the azimuthal direction is also studied, particularly between monitor points located in separate blade channels. The coherence functions in the radial and azimuthal directions between monitor points located in the same blade channel are compared between the 360°and the periodic sector configurations. Lower coherence levels are obtained in the 360°LES mainly at low and mid frequencies.

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Section: Introductionmentioning

confidence: 85%

“…ES is compared to a periodic sector LES, which was performed in a previous work by the authors [12] using the same configuration and numerical setup.…”

Section: Introductionmentioning

confidence: 99%

Direct noise predictions of a 360° full fan stage using LES

Al-Am

Clair

Giauque

et al. 2023

AIAA AVIATION 2023 Forum

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“…The findings of this study regarding numerical modelling are relevant to modern ultra high bypass ratio (UHBR) fans such as the composite low-speed fan developed at Ecole Centrale de Lyon [29]. This geometry is known to have a laminar separation bubble at part-speed conditions [21], which is not captured by the URANS methods used for stability analysis [29]. The results presented in this paper indicate that coupled LES simulations or at least validation of transition models in aeroelastic context may be required to accurately predict aerodynamic damping of this configuration.…”

Section: Relevance To Modern Uhbr Fansmentioning

confidence: 99%

“…Properly resolved LES-Simulation is still too costly for aeroelastic studies, as timescales of blade vibration (10 −3 -10 −1 s) differ vastly from relevant turbulent scales (10 −9 -10 −7 s). Application of LES in turbomachinery is hence still limited to non-vibrating configurations [18][19][20][21]. Using unsteady Reynolds-averaged Navier-Stokes (URANS) and coarse large eddy simulations (LES), the flow is analysed and predictions are compared to experimental measurements.…”

Section: Introductionmentioning

confidence: 99%

Near-Stall Modelling of a Pitching Airfoil at High Incidence, Mach Number and Reduced Frequency

Brandstetter

Stapelfeldt

2022

IJTPP

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The prediction accuracy of aeroelastic stability in fans and compressors depends crucially on the accuracy of the underlying aerodynamic predictions. The prevalent approach in the field solves the unsteady Reynolds-averaged Navier—Stokes equations in the presence of blade vibration. Given the unsteady, three-dimensional and often separated nature of the flow in the regimes of aeroelastic interest, the confidence in URANS methods is questionable. This paper uses the simple test case of a pitching symmetric aerofoil with a sharp leading edge to illustrate the challenges of aeroelastic modelling. It compares coupled numerical simulations against time-resolved experimental measurements. The unsteady aerodynamic response of the pitching blade and its dependency on tip-clearance flow and time-averaged incidence angle are analyzed. The results indicate that differences in the unsteady aerodynamics between different numerical approaches close to stall can have a significant impact on local aerodynamic damping. Furthermore, for the chosen test case there is a strong correspondence between the local quasi-steady and unsteady behaviour which weakens, but is still present, towards stall.

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“…The goal of the study presented here is to provide a benchmark dataset on a geometry that is representative of near future architectures that allows detailed validation and calibration of prediction methods on multiple levels of fidelity for the whole research community. This ranges from reduced order models as described by [13,14] to scale resolving coupled methods which are on the verge of being accessible to this type of architecture [15,16,17,18,19].…”

Section: Introductionmentioning

confidence: 99%

Experiments on Tuned UHBR Open-Test-Case Fan ECL5/CATANA: Performance and Aerodynamics

Schneider,

Fiquet,

Paoletti

et al. 2024

Journal of Turbomachinery

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With the advancement of modern fan architectures the lack of experimental benchmarks for the research community became apparent in recent years. Enormous effort in method development could not be validated on representative geometries and motivated the development of the open-test-case ECL5/CATANA. A carbon fibre fan stage has been designed by Ecole Centrale de Lyon and shared with the community in 2021. The fan is representative of modern UHBR architectures with sonic design speed. The reference configuration has been investigated experimentally with multi-physical instrumentation. In this publication the results of the first experimental campaign are presented with a detailed analysis of the aerodynamic performance and system symmetry. The presented results comprise full stage mappings across the whole operating range for three main speedlines (55%, 80% and 100%) using performance rakes, unsteady wallpressure arrays, tip-clearance and stagger-angle measurements. Radial profiles of intake boundary layer and rotor-exit conditions at selected conditions complete the full validation dataset for steady and unsteady aerodynamic simulations. Results are discussed in comparison to blind-test RANS simulations of different international institutes. Significant predicition inaccuracies of the tip flow and corner separations of the stator are observed and reveal the requirement of real-blade-geometry measurements at running conditions. This paper is accompanied by a publication with a focus on aeroelastic instabilities observed near the stability limit. The results represent a comprehensive dimensional benchmark dataset and allow method validation on multiple levels of fidelity for the aerodynamic and aeroelastic research community.

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Direct noise predictions of fan broadband noise using LES and analytical models

Cited by 8 publications

References 37 publications

Direct noise predictions of a 360° full fan stage using LES

Direct noise predictions of a 360° full fan stage using LES

Near-Stall Modelling of a Pitching Airfoil at High Incidence, Mach Number and Reduced Frequency

Experiments on Tuned UHBR Open-Test-Case Fan ECL5/CATANA: Performance and Aerodynamics

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