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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 in quiescent standard ambient conditions 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...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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Yunus, F. (author), Casalino, D. (author), Avallone, F. (author), Ragni, D. (author)This paper presents an atmospheric propagation model, based on ray acoustics, that accounts for realistic weather conditions in the evaluation of the noise footprint of an aircraft. Noise sources, obtained using the Ffowcs Williams and Hawkings acoustic analogy applied to scale-resolved flow simulation data, are stored on a hemisphere...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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Merino Martinez, R. (author), Rubio Carpio, A. (author), Lima Pereira, L.T. (author), van Herk, S.W.L. (author), Avallone, F. (author), Ragni, D. (author), Kotsonis, M. (author)The newly refurbished vertical tunnel (V-tunnel) at Delft University of Technology has been redesigned as a state-of-the-art facility for research in aeroacoustics (A-tunnel), as well as fundamental studies in laminar-turbulent transition and flow control. This manuscript focuses on the design and refurbishment aspects of the facility,...journal article 2020
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Rubio Carpio, A. (author), Avallone, F. (author), Ragni, D. (author), Snellen, M. (author), van der Zwaag, S. (author)An experimental study on broadband noise scattered by permeable trailing edges with different pore arrangements is performed. A NACA 0018 airfoil with chord c = 0.2 m is investigated at chord-based Reynolds numbers ranging from 1.4 × 10<sup>5</sup> to 3.8 × 10<sup>5</sup> and angles of attack of 0.2 and 5.4 degrees. Noise emission from five...journal article 2020
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Gutiérrez, R. (author), Llórente, E. (author), Echeverría, F. (author), Ragni, D. (author)In this study, the aerodynamic performance of a thick airfoil is analysed, after installing leading-edge roughness to emulate a severe state on the airfoil surface. The impact on aerodynamic coefficients has been quantified using two roughness methods: zig-zag tape and sandpaper. Wind tunnel tests are carried out at a Reynolds number of 3•10...journal article 2020
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Avallone, F. (author), Ragni, D. (author), Casalino, D. (author)Lattice-Boltzmann Very-Large-Eddy Simulations of two Diffuser-Augmented Wind Turbines are carried out to investigate the effect of the tip-clearance (TC) ratio on both the flow field and the far-field noise. The DonQi® wind turbine, a three blades ducted rotor with nominal TC of 2.5%, is chosen as reference test case. The second configuration...journal article 2020
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Merino Martinez, R. (author), Luesutthiviboon, S. (author), Zamponi, R. (author), Rubio Carpio, A. (author), Ragni, D. (author), Sijtsma, P. (author), Snellen, M. (author), Schram, Christophe (author)In this paper, the performance of four acoustic imaging methods: conventional frequency domain beamforming (CFDBF), functional beamforming (FUNBF), enhanced high resolution CLEAN–SC (EHR–CLEAN–SC) and generalized inverse beamforming (GIBF), is investigated in terms of accuracy and variability. Three experimental test cases are considered: 1)...journal article 2020
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Lima Pereira, L.T. (author), Ragni, D. (author), Avallone, F. (author), Scarano, F. (author)Abstract: Measurements of distributed surface pressure fluctuations over trailing-edge serrations at a Reynolds number Re <sub>θ</sub> = 4900 are performed with time-resolved 3D particle imaging velocimetry using helium filled soap bubbles as flow tracers. The sparse velocity vector field obtained with Lagrangian particle tracking is densely...journal article 2020
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Llorente, Elena (author), Ragni, D. (author)An experimental study focusing on the change of the aerodynamic performance of a wind turbine with the employment of trailing-edge serrations is presented. The design procedure which starts from the serration design, together with the experimental wind tunnel testing and the installation in an already operating wind turbine is discussed. A...journal article 2020
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VanDercreek, Colin (author), Merino Martinez, R. (author), Snellen, M. (author), Ragni, D. (author), Simons, D.G. (author)This paper analyses the influence of microphone cavity geometry on beamforming measurements with a turbulent boundary layer present on the microphone array. A 16- microphone array was tested in the anechoic open-jet wind tunnel of the Delft University of Technology. The array was placed on a flat plate mounted flush with the exit nozzle of the...conference paper 2020
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Zamponi, R. (author), Satcunanathan, S. (author), Moreau, S. (author), Ragni, D. (author), Meinke, M. (author), Schröder, W. (author), Schram, C. (author)A possible strategy for the reduction of the aeroacoustic noise generated by turbulence interacting with a wing profile, also referred to as leading-edge noise, is represented by the implementation of a porous medium in the structure of the airfoil. However, the physical mechanisms involved in this noise mitigation technique remain unclear....journal article 2020
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Teruna, C. (author), Manegar, F.A. (author), Avallone, F. (author), Ragni, D. (author), Casalino, D. (author), Carolus, T. (author)Open-cell porous materials have been reported as a promising concept for mitigating turbulent boundary-layer trailing-edge noise. This manuscript examines the aeroacoustics of a porous trailing edge to study its noise reduction mechanisms. Numerical investigations have been carried out for a NACA 0018 aerofoil with three different types of...journal article 2020
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Jaiswal, P. (author), Moreau, Stéphane (author), Avallone, F. (author), Ragni, D. (author), Pröbsting, S. (author)Two-point velocity statistics near the trailing edge of a controlled diffusion airfoil are obtained, both experimentally and analytically, by decomposing Poisson's equation for pressure into the mean-shear (MS) and turbulence-turbulence (TT) interaction terms. The study focuses on the modeling of each interaction term, in order to allow for...journal article 2020
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Rego, L. (author), Avallone, F. (author), Ragni, D. (author), Casalino, D. (author)The link between jet-installation noise and the near-field flow features of the corresponding isolated jet is studied by means of lattice-Boltzmann numerical simulations. The computational set-up consists of a flat plate placed in proximity to a jet, replicating the interaction benchmark study carried out at NASA Glenn. Installation effects...journal article 2020
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Romani, G. (author), Ye, Q. (author), Avallone, F. (author), Ragni, D. (author), Casalino, D. (author)Aim of this paper is to investigate the effects of the turbulent flow developing over a fuselage on fan noise for BLI embedded propulsion systems. Such configurations can suffer from inlet flow distortions and ingestion of turbulence at the fan plane with consequent impact on both broadband and tonal fan noise. The analysis is performed on a...journal article 2020
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Barrio, J. Fernández (author), Mertens, C. (author), Ragni, D. (author), Sciacchitano, A. (author), van Oudheusden, B.W. (author)A proportionate controller is investigated experimentally for unsteady load alleviation purposes on a 2D wing model with a trailing-edge flap. The controller acts on the velocity of the flaps, and pressure sensors are used to detect the unsteady loads, which are generated by actuating the wing model in a sinusoidal motion. Two different...journal article 2020
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VanDercreek, Colin (author), Amiri Simkooei, A. (author), Snellen, M. (author), Ragni, D. (author)This study investigates how embedding microphones in different cavity geometries along the wall of a wind tunnel reduces the measured turbulent boundary layer pressure fluctuations. The effect of these cavities on the measured signal-to-noise ratio of an acoustic source with flow present was also quantified. Twelve cavity geometries defined...journal article 2019