Searched for: subject%3A%22noise%22
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Fiscaletti, D. (author), Lima Pereira, L.T. (author), Ragni, D. (author)
The present study focuses on the application of finlet rails as a passive technique of flow control to mitigate trailing-edge noise. Finlet rails are small cylinders whose axes are aligned along the streamwise direction, transversally positioned with respect to the trailing edge. In the first part of this study, the effects of finlet geometry...
journal article 2024
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Zamponi, R. (author), Avallone, F. (author), Ragni, D. (author), Schram, C. (author), van der Zwaag, S. (author)
This paper elucidates the link between the near-wake development of a circular cylinder coated with a porous material in a low Mach-number flow and the related aerodynamic sound attenuation. It accomplishes this by formulating the cylinder flow-induced noise as a diffraction problem. The necessity for such an approach is driven by...
journal article 2024
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Lima Pereira, L.T. (author), Avallone, F. (author), Ragni, D. (author), Scarano, F. (author)
This work discusses the physics of noise reduction achieved from serrated trailing–edges and its impact by the serration design. An experimental campaign is carried out with a benchmark 2D model based on a NACA 63<sub>3</sub>–018 airfoil. Different trailing-edge serrations are tested under several flow speeds and angles of attack conditions...
journal article 2023
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Yunus, F. (author), Casalino, D. (author), Avallone, F. (author), Ragni, D. (author)
Efficient calculation of urban air mobility noise footprint in a vertiport environment, considering acoustic effects of various designs, operational conditions, and environmental factors, is essential to limit the noise impact on the community at an early stage. To this purpose, the computationally efficient low-fidelity approach presented by...
journal article 2023
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Avallone, F. (author), Ragni, D. (author)
Noise reduction is one of the major challenges to the societal acceptance of wind turbines. Aerodynamic noise sources are the dominant ones, assuming that mechanical noise can be reduced by correct insulation and periodic maintenance of the gearbox and drive train and by adding insulating material in the wind-turbine nacelle. The dominant...
book chapter 2023
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Meloni, S. (author), de Paola, E. (author), Grande, E. (author), Ragni, D. (author), Stoica, L. G. (author), Di Marco, A. (author), Camussi, R. (author)
Propeller noise generally exhibits a rich mixture of tonal and broadband components related to different physical mechanisms. Specifically, the tones are characterized by having deterministic and persistent characteristics, while the broadband counterpart has random behaviour. The separation is essential for the experimenters as they provide...
journal article 2023
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Teruna, C. (author), Rego, Leandro (author), Casalino, D. (author), Ragni, D. (author), Avallone, F. (author)
This manuscript presents the application of a recently developed noise reduction technology, constituted by poro-serrated stator blades on a full-scale aircraft model, in order to reduce rotor-stator interaction noise in the fan stage. This study was carried out using the commercial lattice Boltzmann solver 3DS-SIMULIA PowerFLOW. The simulation...
journal article 2022
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Candeloro, Paolo (author), Ragni, D. (author), Pagliaroli, Tiziano (author)
In the last decade, the drone market has grown rapidly for both civil and military purposes. Due to their versatility, the demand for drones is constantly increasing, with several industrial players joining the venture to transfer urban mobility to the air. This has exacerbated the problem of noise pollution, mainly due to the relatively lower...
journal article 2022
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Rego, Leandro (author), Avallone, F. (author), Ragni, D. (author), Casalino, D. (author)
This paper investigates the mechanisms by which flow-permeable materials provide noise reduction in an installed jet configuration. Numerical simulations are carried out with a flat plate placed in the near field of a single-stream subsonic jet (M<sub>a</sub>=0.3 and M<sub>a</sub>=0.5). The trailing-edge region of the plate is replaced by...
journal article 2022
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Yunus, F. (author), Grande, E. (author), Casalino, D. (author), Avallone, F. (author), Ragni, D. (author)
A noise footprint prediction framework for propeller-driven aircraft which couples an aerodynamic model and several aeroacoustic models is presented in this study. The aerodynamic model is based on the blade element momentum theory, while the aeroacoustic models are based on a time-domain compact dipole/monopole Ffowcs-Williams and Hawking's...
journal article 2022
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Lima Pereira, L.T. (author), Avallone, F. (author), Ragni, D. (author), Scarano, F. (author)
A physical description of the flow mechanisms that govern the distribution of the wall-pressure fluctuations over the surface of a serrated trailing edge is proposed. Three main mechanisms that define the variation of turbulent pressure fluctuations across the serrated edge are discussed and semi-empirical models are formulated accordingly....
journal article 2022
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Ragni, D. (author), Avallone, F. (author), Casalino, D. (author)
Sustainability has encouraged studies focusing on lowering the aeroacoustic impact of new aerodynamically optimized mechanical systems for several applications in wind-energy, aviation, automotive and urban air-mobility. The deployment of effective noise-reduction strategies starts with a deep understanding of the underlying mechanisms of...
review 2022
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Rego, Leandro (author), Avallone, F. (author), Ragni, D. (author), Casalino, D. (author), Denayer, Hervé (author)
A Helmholtz resonator with a curved cavity is studied for reducing jet-installation noise in a configuration comprised by a subsonic jet and a nearby flat plate. The face-sheet and cavity are designed with the Guess method and the impedance is verified through an experiment and a simulation of an impedance tube. Both single and double degree...
journal article 2022
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Mourão Bento, H.F. (author), Ragni, D. (author), Avallone, F. (author), Simons, D.G. (author), Snellen, M. (author)
Sound absorbing porous materials are used to line a wind tunnel wall, in order to reduce reflections. However, the lining can have a detrimental effect on the acoustic measurements due to an increase in the noise radiated from the walls. In addition, the aerodynamic fidelity of the tunnel can be affected. In the present study, the influence...
journal article 2022
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Luesutthiviboon, S. (author), Ragni, D. (author), Avallone, F. (author), Snellen, M. (author)
This study focuses upon a new permeable topology design concept as an alternative to porous metal foams, for turbulent boundary layer trailing-edge (TBL-TE) noise attenuation. The present permeable topology has unconventional characteristics with respect to the metal foams: a combination of low flow resistivity r and high form drag...
journal article 2021
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Casalino, D. (author), Grande, E. (author), Romani, G. (author), Ragni, D. (author), Avallone, F. (author)
Experimental and numerical results of a propeller of 0.3 m diameter operated at 5000 RPM and axial velocity ranging from 0 to 20 m/s and advance ratio ranging from 0 to 0.8 are presented as a preliminary step towards the definition of a benchmark configuration for low Reynolds number propeller aeroacoustics. The corresponding rotational tip...
journal article 2021
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Rego, Leandro (author), Ragni, D. (author), Avallone, F. (author), Casalino, D. (author), Zamponi, R. (author), Schram, Christophe (author)
This paper investigates the application of flow-permeable materials as a solution for reducing jet-installation noise. Experiments are carried out with a flat plate placed in the near field of a single-stream subsonic jet. The flat plate is modular and the solid surface near the trailing edge can be replaced with different flow-permeable...
journal article 2021
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Lima Pereira, L.T. (author), Merino Martinez, R. (author), Ragni, D. (author), Gómez-Ariza, David (author), Snellen, M. (author)
This paper explores the advantages of combining asynchronous microphone array measurements for acoustic source mapping in two and three–dimensional applications. Four different approaches are considered, three consisting of the combination of the source maps (arithmetic mean, geometric mean, and minimum value), and a fourth one obtained by...
journal article 2021
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Teruna, C. (author), Rego, Leandro (author), Avallone, F. (author), Ragni, D. (author), Casalino, D. (author)
Porous materials have been widely investigated as a mean for noise reduction. Numerical simulations can be used to investigate the physical mechanisms responsible for noise reduction; however, a correct modeling of the porous medium through an equivalent fluid model is essential to minimize the computational costs. This paper reports a...
journal article 2021
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Teruna, C. (author), Avallone, F. (author), Ragni, D. (author), Rubio Carpio, A. (author), Casalino, D. (author)
Lattice Boltzmann simulations were carried out to investigate the noise mitigation mechanisms of a 3-D printed porous trailing-edge insert, elucidating the link between noise reduction and material permeability. The porous insert is based on a unit cell resembling a lattice of diamond atoms. It replaces the last 20 % chord of a NACA 0018 at...
journal article 2021
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