Fast Multipole Boundary Element Method with Stochastic Sources for Broadband Noise Simulation

Reiche, Nils; Ewert, Roland; Lummer, Markus; Delfs, Jan

doi:10.2514/6.2017-3515

Cited by 6 publications

(4 citation statements)

References 16 publications

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“…The FMCAS 6 is a numerical algorithm developed at the Department of Technical Acoustics in DLR-Braunschweig to calculate the sound radiated from a sound source close to a body using the Boundary Element Method. The use of FRPM presented in Section 2.1 coupled with the Boundary Element Method to calculate the far-field noise was proposed and validated in Reiche et al 10,13 The Helmholtz equation relates the second-order spatial derivative of the pressure p to the sound source f, wherebrepresents parameters in the frequency domain,…”

Section: Fmcasmentioning

confidence: 99%

“…by substituting Equation (10) to Equation (9). Turbulence interaction with the surface is established by coupling the acoustic velocity, ûn,a , and the incompressible velocity, ûn,ic , or ûn ¼ ûn,a ¼ ûn,ic .…”

Section: Fmcasmentioning

confidence: 99%

“…A summary of the FRPM/FMCAS simulation that is relevant for the present study is given below. For a complete description, the authors suggest previous studies 7–10 …”

Section: Numerical Proceduresmentioning

confidence: 99%

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Noise simulations of flap devices for wind turbine rotors

et al. 2022

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The rotor of a large diameter wind turbine experiences more substantial and more dynamic loads due to the fluctuating and heterogeneous wind field. The project SmartBlades 2.0 investigated rotor blade design concepts that alleviate aerodynamic loading using active and passive mechanisms. The present work evaluates the acoustics of the two load alleviating concepts separately, an inboard slat and an outboard flap, using the Fast Random Particle Mesh/Fast Multipole Code for Acoustic Shielding (FRPM/FMCAS) numerical prediction toolchain developed at DLR with input from the averaged flow field from RANS. The numerical tools produce a comparable flap side-edge noise spectrum with that of the measurement conducted in the Acoustic Wind Tunnel Braunschweig (AWB). The validated FRPM/FMCAS was then used to analyze the self-noise from a slat at the inboard section of a rotor blade with a 44.45 m radius and compared with that from the outboard trailing edge. Furthermore, the rotational effect of the rotor was included in the post-processing to emulate the noise observed at ground level. The findings show an increase in the slat's overall sound pressure level and a maximum radiation upwind of the wind turbine for the case with the largest wind speed that represents the off-design condition. In operational conditions, the slat adds at most 2 dB to the overall sound pressure level.The toolchain evaluates wind turbine noise with conventional or unconventional blade design, and the problem can be scaled up for a full-scale analysis. As such, the tools presented can be used to design low-noise wind turbines efficiently.

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Section: Fmcasmentioning

confidence: 99%

Section: Fmcasmentioning

confidence: 99%

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Noise simulations of flap devices for wind turbine rotors

et al. 2022

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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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