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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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Boatto, U. (author), Bonnet, Jean-Paul (author), Avallone, F. (author), Ragni, D. (author)The design of efficient rotor blades is affected by the accuracy of aerodynamic prediction methods for load distributions and power computations. Research showed that the accuracy of BEMT-based industrial codes decreases at high inflow-speed under uniform aligned steady conditions. The identified reasons are inaccuracies in the semi-empirical...conference paper 2023
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Zoppini, G. (author), Sequeira, A.D. (author), Michelis, Theodorus (author), Ragni, D. (author), Kotsonis, M. (author)The present work details the steady and unsteady flow topology in the vicinity of an array of periodically spaced super-critical (i.e. causing flow tripping) discrete roughness elements (DRE) applied in a swept wing boundary layer. The stationary flow field is acquired by means of high-magnification dual-pulse tomographic particle tracking...conference paper 2023
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Terracol, Marc (author), Manueco, Lucas (author), Manoha, Eric (author), Avallone, F. (author), Ragni, D. (author), Rubio Carpio, A. (author)This study presents a numerical investigation of the noise mitigation effect provided by several fairings placed upstream of a simplified two-wheel landing gear. The chosen configuration is equipped with detachable elements that mimic realistic components, e.g. brakes and torque link, to include representative landing gear noise sources. Several...conference paper 2023
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do Nascimento Monteiro, F. (author), Ragni, D. (author), Avallone, F. (author), Sinnige, T. (author)A low-order numerical tool for estimating noise emissions from distributed propeller configurations is presented. The paper describes the tool's computational framework, which uses Hanson's near-field theory to calculate the thickness and loading noise components. The formulation assumes steady blade loading, but an unsteady case can be handled...conference paper 2023
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Dekker, H.N.J. (author), Tuinstra, M (author), Baars, W.J. (author), Scarano, F. (author), Ragni, D. (author)A semi-emperical model is developed, able to capture the aeropropulsive performance characteristics of Over-The-Wing propellers at incidence. The model is based on an hypothesis on the interactions of the propeller- and wing-induced flow fields. Effects of these interactions on the both the thrust and lift are written in a form in which the...conference paper 2023
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Baars, W.J. (author), Ragni, D. (author)Rotor noise comprises harmonic features, related to the blade passing frequency, as well as broadband noise. Even though acoustic spectra yield frequency-distributions of acoustic energy within pressure time series, they do not reveal phase-relations between different frequency components. The latter are of critical importance for the...conference paper 2023
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Trascinelli, L. (author), Bowen, Luke (author), Piccolo, A. (author), Zamponi, R. (author), Ragni, D. (author), Avallone, F. (author), Zhou, Beckett Y. (author), Zang, Bin (author)The present study assesses the ability to numerically predict turbulence-interaction noise of a NACA0012 airfoil with grid-generated turbulence by utilizing the Lattice Boltzmann solver PowerFLOW. Both the near-field flow characteristics and far field noise are bench-marked against an existing experimental study. The grid was chosen to match...conference paper 2023
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Zarri, Alessandro (author), Koutsoukos, P.A. (author), Avallone, F. (author), de Prenter, Frits (author), Ragni, D. (author), Casalino, D. (author)Distributed electric propulsion systems are an emerging technology with the potential of revolutionizing the design and performance of aircraft. When propellers are located in close proximity, they can be subjected to aerodynamic interactions, which affect the far-field noise. In this paper, we study an array of three co-rotating and adjacent...conference paper 2023
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Piccolo, A. (author), Zamponi, R. (author), Avallone, F. (author), Ragni, D. (author)The analytical model for leading-edge noise prediction formulated by Amiet, developed for a flat plate, relates the far-field acoustic pressure to the upstream inflow conditions, modeled by canonical turbulence spectra. The inaccurate results provided by this low-fidelity method when applied to thick airfoils has been attributed to the...conference paper 2023
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Mourão Bento, H.F. (author), VanDercreek, Colin (author), Avallone, F. (author), Ragni, D. (author), Sijtsma, P. (author), Snellen, M. (author)Aeroacoustic tests in closed wind tunnels are affected by reflections in the tunnel circuit and background noise. Reflections can be mitigated by lining the tunnel circuit. The present study investigates if lining exclusively the most accessible segment of a closed wind tunnel circuit, in particular the test section, is an approach which...conference paper 2023
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Lima Pereira, L.T. (author), Avallone, F. (author), Ragni, D. (author), Buck, Steven (author), Oerlemans, S. (author)This work proposes a semi-empirical framework to predict the noise of wind turbines with serrated trailing edge blades. The framework is employed for studying the reduction of the noise of the SWT 2.3-93 benchmark wind turbine. The framework is verified against field acoustic measurements of the real wind-turbine model and of noise reduction...conference paper 2023
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Kalyani, S.K. (author), Jaiswal, P. (author), Rendón, Jose (author), Moreau, Stéphane (author), Ragni, D. (author)The present experimental investigation focuses on a flow-field and noise characterization of a CD airfoil experiencing large flow separation and stall. Measurements are performed to investigate the effect of Reynolds number stalling noise signature of the CD airfoil. This study includes investigation of the potential interaction of wind tunnel...conference paper 2023
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Luesutthiviboon, S. (author), Meirelles Pereira, L. (author), Ragni, D. (author), Avallone, F. (author), Snellen, M. (author)The authors would like to provide the following corrections and clarifications to the article titled “Aeroacoustic Benchmarking of Trailing-edge Noise from a NACA 633–018 Airfoil with Trailing-edge Serrations” which has been published in the AIAA Journal Vol. 61, No. 1, and can be accessed online via https://doi.org/10.2514/1.J061630. The first...journal article 2023
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Luesutthiviboon, S. (author), Lima Pereira, L.T. (author), Ragni, D. (author), Avallone, F. (author), Snellen, M. (author)Experimental results on trailing-edge (TE) noise from a NACA 63<sub>3</sub> –018 airfoil are presented for a chord-based Reynolds number Re<sub>c</sub> range between 2 × 10<sup>5</sup> and 3 × 10<sup>6</sup>. Far-field TE noise from the baseline airfoil with a straight TE and TE serrations is measured with varying Re<sub>c</sub>, angle of...journal article 2023
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Yunus, F. (author), Casalino, D. (author), Avallone, F. (author), Ragni, D. (author)This paper presents a noise propagation approach based on the Gaussian beam tracing (GBT) method that accounts for multiple reflections over three-dimensional terrain topology and atmospheric refraction due to horizontal and vertical variability in wind velocity. A semi-empirical formulation is derived to reduce truncation error in the beam...journal article 2023
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Zoppini, G. (author), Michelis, Theodorus (author), Ragni, D. (author), Kotsonis, M. (author)This work presents the first experimental characterization of the flow field in the vicinity of periodically spaced discrete roughness elements (DRE) in a swept wing boundary layer. The time-averaged velocity fields are acquired in a volumetric domain by high-resolution dual-pulse tomographic particle tracking velocimetry. Investigation of...journal article 2023
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- Dekker, H.N.J. (author), Tuinstra, Marthijn (author), Baars, W.J. (author), Scarano, F. (author), Ragni, D. (author) conference paper 2023
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Zamponi, R. (author), Ragni, D. (author), van der Zwaag, S. (author), Avallone, F. (author)The aerodynamic noise radiated by the flow past a cylinder in the subcritical regime can be modeled by a quadrupolar sound source placed at the onset position of the vortex-shedding instability that is scattered by the surface with a dipolar directivity. When the cylinder is coated with a porous material, the intensity of the shed vortices is...journal article 2023