Fan noise shielding predictions with a coupled DG / FM-BEM method for installed aircraft engines

Proskurov, Stanislav; Moessner, Michael; Ewert, Roland; Lummer, Markus; Delfs, Jan

doi:10.2514/6.2021-2167

Cited by 4 publications

(5 citation statements)

References 24 publications

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“…In what follows, the main components of the proposed methodology are briefly described. For details on any of these, the reader is referred to respective publications 12 Here, focus is put on the overall coupled approach and the necessary steps.…”

Section: Methodsmentioning

confidence: 99%

“…Casenave et al 11 realized a coupling between a boundary integral method with a FEM solver in uniform flow for the sound scattering at a cylinder in potential cross flow. Proskurov et al 12 consequently coupled a Discontinuous Galerkin volume resolving code to solve the acoustic perturbation equations (APE) 13 for sound propagation in non-uniform flow with a fast multipole multidomain boundary element solver for the Helmholtz equation, derived from the Taylor transform of Möhring's wave equation.…”

Section: Problem Backgroundmentioning

confidence: 99%

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Extension of the concept of Ffowcs-Williams and Hawkings type wave extrapolation to non-trivial flow effects and exterior surfaces

Delfs

Mößner

Proskurov

et al. 2022

International Journal of Aeroacoustics

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In appreciation of Ffowcs-Williams and Hawkings’ seminal contribution on describing the sound radiation from moving objects, this article discusses a concept of taking into account local non-trivial flow effects on the sound propagation. The approach is motivated by the fact that the numerical simulation of the sound propagation from complete full scale aircraft by means of volume-discretizing (CAA = Computational AeroAcoustics) methods is prohibitively expensive. In fact, a homogeneous use of such CAA approach would waste computational resources since for low speed conditions the sound propagation around the aircraft is subject to very mild flow effects almost everywhere and may be treated by more inexpensive methods. The part of the domain, where the sound propagation is subject to strong flow effects and thus requiring the use of CAA is quite restricted. These circumstances may be exploited given a consistent coupling of methods. The proposed concept is based on the strong (alternatively weak) coupling of a volume discretizing solver for the Acoustic Perturbation Equations (APE) and a modified Ffowcs-Williams and Hawkings (FW-H) type acoustic integral. The approach is established in the frequency domain and requires two basic ingredients, namely a) a volume discretizing solver for the APE, or for Möhring-Howe’s aeroacoustic analogy, to take into account strong non trivial flow effects like refraction at shear flows wherever necessary, and b) an aeroacoustic integral equation for the propagation part in areas where non-potential mean flow effects are negligible. The coupling of this aeroacoustic integral and the APE solver may be realized in a strong (i.e. two-ways) form in which both components feed back information into one another, or in a weak form (i.e. one-way), in which the sound field output data from the APE solver serves as given input for the integral equation. If an aircraft geometry has minor influence on the sound radiation to arbitrary observer positions, the aeroacoustic integrals may simply be evaluated explicitly. If on the other hand, the presence of the geometry has an important influence on the sound radiation, then the acoustic integral equation is implicit and requires some sort of numerical solution, in this case a Fast Multipole Boundary Element solver. While conceptually the weak coupling follows the spirit of the FW-H approach to describe sound propagation from aeroacoustic sources the underlying aeroacoustic integral is not based on Lighthill’s analogy, but the aeroacoustic analogy of Möhring-Howe. This is a consequence of the fact that in the two way-coupling the acoustic particle velocity in a moving medium needs to be determined, which is non-trivial based on an acoustic integral. As an important feature of the strong coupling the acoustic integral also provides practically perfect non-reflection boundary conditions even when the desireably small CAA domain does not extend into the far field. The validity of the presented computation approach is demonstrated in two example use cases.

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Section: Methodsmentioning

confidence: 99%

Section: Problem Backgroundmentioning

confidence: 99%

Extension of the concept of Ffowcs-Williams and Hawkings type wave extrapolation to non-trivial flow effects and exterior surfaces

Delfs

Mößner

Proskurov

et al. 2022

International Journal of Aeroacoustics

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“…Hence, integral techniques that can predict far-field signals based solely on the near-field are in wide use. Alternate strategies, such as solving a simplified differential equation out to the midfield [1][2][3][4][5][6] have shown promise, but their success is highly dependent on the accuracy and stability of the method used to either model the source or extract some measure of the acoustic source from a numerical solution of the near-field. Nonetheless, the relative simplicity of implementation of integral solutions of the Ffowcs Williams and Hawkings 7 (FW-H) equation has led to widespread adoption with URANS, DES, 8 and now LES flow solvers.…”

Section: Introductionmentioning

confidence: 99%

Airframe noise predictions using the Ffowcs Williams-Hawkings equation

Lockard

2022

International Journal of Aeroacoustics

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This paper considers potential sources of error when using the Ffowcs Williams-Hawkings equation to make predictions of airframe noise, which entails a relatively low-speed, uniform incoming flow encountering geometry of varying complexity. Numerical simulations are used to investigate several model problems where Ffowcs Williams-Hawkings integration surfaces are placed on solid surfaces as well as in the flow. Comparisons with the pressure obtained directly from the simulations reveal that when solid surfaces are used, the acoustic calculations can produce erroneous results in upstream directions and when scattering bodies block the line of sight from observers to the source. Using solid surface input data implies ignoring all volumetric source effects, which include noise generation as well as flow effects. Nonuniform flow alone, such as is found in a steady boundary layer, was not found to be a significant source of error, so the amplitude and phase changes induced by turbulent eddies in massively separated flow regions is speculated to be the primary cause of the error.

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“…E ngine integration and the effects on noise source mechanisms are necessary to assess future agile aircraft designs in early design phases. The actual position of the propulsion system relative to the aircraft's planform directly impacts the noise sources and radiation directivities [1]. Intake and exhaust integration can cause complex propagation phenomena.…”

Section: Introductionmentioning

confidence: 99%

“…With the effect of engine noise shielding the integrated design can imply benefits regarding low noise technologies. Fan tone shielding and noise scattering of the MULDICON intake were numerically investigated by Proskurov with a Discontinuous Galerkin method for different frequency modes [1]. In order to validate the numerical methods a modular acoustic wind tunnel model of the MULDICON with a wing span of 2 m was manufactured.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigations on acoustic propagation effects for highly integrated intake ducts

Patrick

Kolb

Mancini

et al. 2022

28th AIAA/CEAS Aeroacoustics 2022 Conference

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Aeroacoustic assessment of highly integrated propulsionsystems is a challenging task at an early design stage and requires detailed physical understanding with validated numerical prediction capabilities. This work presents numerical studies of an UCAV configuration with a complex intake duct as a complementary analysis to measurements. The setup is based on the agile (unmanned) NATO air vehicle MULDICON UCAV (MULti-DIsciplinary CONfiguration) with an S-shaped intake duct to primarily shield the engine from radar. A laser-based sound source is modeled as monopole in the intake duct. The computation of the acoustic field is performed in the time domain with the Discontinuous Galerkin (DG) code DISCO++ developed by DLR. RANS mean flow fields are calculated with DLR's TAU solver as background flow input for the aeroacoustic noise propagation. A parametric study is conducted for the monopole sound source. Dependencies of the noise propagation on the intake mass flow rate and the ambient flow velocity are investigated by directivities and spectral characteristics.

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Fan noise shielding predictions with a coupled DG / FM-BEM method for installed aircraft engines

Cited by 4 publications

References 24 publications

Extension of the concept of Ffowcs-Williams and Hawkings type wave extrapolation to non-trivial flow effects and exterior surfaces

Extension of the concept of Ffowcs-Williams and Hawkings type wave extrapolation to non-trivial flow effects and exterior surfaces

Airframe noise predictions using the Ffowcs Williams-Hawkings equation

Numerical investigations on acoustic propagation effects for highly integrated intake ducts

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