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Bennett, Gareth J. (author), Lai, Jiang (author), O'Brien, Gordon C. (author), Ragni, D. (author), Avallone, F. (author), Rubio Carpio, A. (author), Pott-Pollenske, Michael (author)This paper examines the use of both flow control and passive low noise technologies to reduce the aerodynamic noise radiated from a modified LAGOON landing gear, as tested in the EU funded H2020 collaborative research project: INVENTOR, InnoVative dEsign of iNstalled airframe componenTs for aircraft nOise Reduction. At approach to landing,...conference paper 2022
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Kalyani, S.K. (author), Moreau, Stéphane (author), Ragni, D. (author)The present experimental investigation in the anechoic wind tunnel of university of Sherbrooke focuses on the flow-field and noise characterization of a Controlled Diffusion (CD) airfoil, with the flow transitioning from an attached boundary layer at 15◦ incidence to a completely detached one (deep stall) at 22◦ incidence. Simultaneous unsteady...conference paper 2022
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Yunus, F. (author), Casalino, D. (author), Avallone, F. (author), Ragni, D. (author)This work presents a novel noise propagation approach based on the Gaussian Beam Tracing (GBT) method that accounts for complex source directivity, weather conditions, and irregular ground topology for the evaluation of the noise footprint. The approach takes a precomputed noise sphere as input and propagates the acoustic pressure...conference paper 2022
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Grande, E. (author), Ragni, D. (author), Avallone, F. (author), Casalino, D. (author)This paper explains the presence and relevance of noise caused by a laminar separation bubble (LSB) on a propeller operating at low-Reynolds number. Microphone measurements of a propeller with both clean and forced boundary layer transition blades are carried out in an anechoic wind tunnel by varying the propeller advance ratio J from 0 to 0...conference paper 2022
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Rego, Leandro (author), Zamponi, R. (author), Ragni, D. (author), Avallone, F. (author), Casalino, D. (author), Cruellas Bordes, M. (author)An experimental investigation on jet-installation noise reduction with permeable flaps on an aircraft half-model is performed, focusing on the effects on the noise levels as well as on the aerodynamic properties of the model (lift and drag forces). A nozzle with an exit diameter = 113 mm is included for generating a single-stream jet flow in...conference paper 2022
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Gondrum, M. (author), Niemöller, A. (author), Meinke, M. (author), Schröder, W. (author), Rubio Carpio, A. (author), Ragni, D. (author), Avallone, F. (author)The time resolved flow and acoustic fields around a simplified two-wheel nose landing gear configuration featuring brakes, torque link, and a detachable fairing are investigated by numerical and experimental means. The flow field is computed by a lattice Boltzmann method with a collision step based on countable cumulants. Numerical near field...conference paper 2022
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Nederlof, R. (author), Ragni, D. (author), Sinnige, T. (author)The use of electric motors enables a more flexible operation of propellers compared to conventional combustion engines. One possible benefit is the easier operation at negative thrust, which could be beneficial for energy recovery, control purposes, and lower noise through steeper descents. By changing the pitch of the propellers and actively...conference paper 2022
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Zoppini, G. (author), Michelis, Theodorus (author), Ragni, D. (author), Kotsonis, M. (author)This work presents the first reported experimental characterization of the flow field in the direct vicinity of discrete roughness elements (DRE), in a swept wing boundary layer. High magnification tomographic Particle Tracking Velocimetry (3D-PTV) measurements are used to acquire time-averaged velocity and standard deviation fields in a 3D...conference paper 2022
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Zoppini, G. (author), Ragni, D. (author), Kotsonis, M. (author)An experimental parametric study of the effect of discrete roughness elements (DRE) on the development and breakdown of stationary crossflow instability on a swept wing is presented. A systematic investigation of the receptivity to various elements height and chord locations is carried out in a crossflow dominated flow. The flow is globally and...conference paper 2021
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Teruna, C. (author), Avallone, F. (author), Ragni, D. (author), Casalino, D. (author), Rubio Carpio, A. (author)This manuscript presents a numerical investigation of an open-cell 3D-printed perme-able/porous insert used to reduce turbulent boundary layer-trailing edge (TBL-TE) noise. The matrix topology of the insert resembles the lattice of diamond atoms, and thus, it is also referred to as the diamond trailing edge (TE). The porous insert replaces...conference paper 2021
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Arcondoulis, Elias J. G. (author), Liu, Yu (author), Yang, Yannian (author), Ragni, D. (author), Rubio Carpio, A. (author), Avallone, F. (author)View Video Presentation: https://doi-org.tudelft.idm.oclc.org/10.2514/6.2021-2226.vid<br/><br/>The mechanisms responsible for vortex shedding reduction, due to the application of a porous coating to a smooth cylinder placed in uniform flow, are still uncertain despite several numerical and experimental studies. To help understand these...conference paper 2021
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Zamponi, R. (author), Schram, C (author), Moreau, S. (author), Ragni, D. (author)View Video Presentation: https://doi-org.tudelft.idm.oclc.org/10.2514/6.2021-2289.vid<br/><br/>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....conference paper 2021
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Lima Pereira, L.T. (author), Avallone, F. (author), Ragni, D. (author)iew Video Presentation: https://doi-org.tudelft.idm.oclc.org/10.2514/6.2021-2179.vid<br/><br/>The unsteady surface pressure fluctuations over trailing-edge serrations retrofitted to the benchmark NACA 633-018 profile are experimentally measured. Miniaturized unsteady pressure transducers installed on the serration surface are used to describe...conference paper 2021
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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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Avallone, F. (author), Manjunath, P. (author), Ragni, D. (author), Casalino, D. (author)A lattice-Boltzmann Very Large Eddy simulation of a multi-orifice acoustic liner, grazed by a turbulent flow at Mach number equal to 0:3 and a planar acoustic wave with amplitude equal to 130 dB and frequency equal to 1800 Hz, is carried out. The geometry of the liner replicates the experiments carried out in the Grazing Flow Impedance Tube ...conference paper 2019
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Raiola, Marco (author), Ragni, D. (author)The present study proposes a data-driven strategy to extract the dynamics of wave-packets from low-speed velocity field measurements. The flow field under study is a subsonic turbulent round jet at Re = 33000, measured over a 20-nozzle-diameters domain in the axial direction using low-repetition-rate planar Particle Image Velocimetry. The...conference paper 2019
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Ye, Q. (author), Avallone, F. (author), Ragni, D. (author), Choudhari, Meelan (author), Casalino, D. (author)The effects of a finite, spanwise-periodic array of cylindrical roughness elements on boundary layer transition over a NACA 0012 airfoil are investigated at a chord-based Reynolds number of 1.44×10<sup>5</sup> by using hotwire anemometry and infrared thermography. Both the number and the spanwise spacing of roughness elements in the array are...conference paper 2019
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Rego, Leandro (author), Avallone, F. (author), Ragni, D. (author), Casalino, D. (author)A numerical investigation on jet-installation noise is performed using a software based on the Lattice-Boltzmann Method. A flat plate is placed in the irrotational hydrodynamic field of the jet, i.e. outside of the plume, resulting in noise increase due to the scattering of instability waves at the plate trailing edge. The configuration adopted...conference paper 2019
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Zamponi, R. (author), Ragni, D. (author), Van de Wyer, N. (author), Schram, C. (author)The present work aims at evaluating the effectiveness of the use of porous materials for reducing airfoil turbulence-impingement noise. To pursue this objective, a porous NACA-0024 profile filled with melamine foam has been designed for comparison with a solid model. The porous media constituting the airfoil has been fully characterized in...conference paper 2019
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Avallone, F. (author), Casalino, D. (author), Ragni, D. (author)A computational study of two Diffuser-Augmented Wind Turbines (DAWTs) is carried out to investigate both the hydrodynamic flow field and the far-field noise. The two configurations differ for the tip-clearance ratio, defined as the ratio between the tip clearance and the rotor radius. The DonQi® wind turbine, a three blades ducted rotor, is...conference paper 2019