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De Oliveira Andrade, G.L. (author), Balbino dos Santos Pereira, R. (author), van Bussel, G.J.W. (author), Avallone, F. (author), Ragni, D. (author)Flow augmentation consists in modifying mass flow across the actuation plane of a rotor to enhance energy extraction or propulsive efficiency. The talk sketches the distinction between passive and active rotor augmentation strategies. Power coefficient trends are compared analytically while numerical results illustrate differences in flow...abstract 2017
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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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Sinnige, T. (author), Malgoezar, A.M.N. (author), Ragni, D. (author), Snellen, M. (author), Eitelberg, G. (author), Veldhuis, L.L.M. (author)An experimental investigation was performed at the Large Low-speed Facility of the German-Dutch wind tunnels (DNW-LLF) to study the pylon interactions associated with pusher propellers. The aerodynamic and aeroacoustic effects of pylon trailing edge blowing and swirl recovery vanes (SRVs) were evaluated. The pylon installation increased the...conference paper 2015
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Baldacchino, D. (author), Ragni, D. (author), Simao Ferreira, C.J. (author), Van Bussel, G.J.W. (author)In this work, the measured modulated integral boundary layer (IBL) characteristics of low-profile vortex generators (VGs) are used to validate new developments in a viscousinviscid interaction code which is modified to incorporate the effect of the passive mixing devices. The motivations are laid out and sample validation data is presented...conference paper 2015
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- Ashok, A. (author), Ragni, D. (author), Van Oudheusden, B.W. (author), Scarano, F. (author) conference paper 2008
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- Ashok, A. (author), Ragni, D. (author), Van Oudheusden, B.W. (author), Scarano, F. (author) conference paper 2008
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Avallone, F. (author), Ragni, D. (author), Schrijer, F.F.J. (author), Scarano, F. (author), Cardone, G. (author)In this study, the mean flow organization in the symmetry plane of the recirculation region ahead of a cylindrical roughness element immersed in an incoming laminar boundary layer at Mach number equal to 6.5 is investigated. The flow topology is inspected with planar particle image velocimetry (PIV), InfraRed (IR) Thermography and Schlieren flow...conference paper 2015
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Lignarolo, L. (author), Ragni, D. (author), Simao Ferreira, C.J. (author), van Bussel, G.J.W. (author)The present paper is the summary of 3 years of research on the wake aerodynamics of horizontal axis wind turbine at Delft University of Technology, the Netherlands. In particular, the main results and the conclusions of two experimental campaigns are collected. The underlying research question is: how do the near-wake turbulent flow structures...conference paper 2015
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Azijli, I. (author), Sciacchitano, A. (author), Ragni, D. (author), Palha da Silva Clerigo, A. (author), Dwight, R.P. (author)The present work proposes a methodology for the a posteriori quantification of the uncertainty of pressure data retrieved from PIV measurements. It relies upon the Bayesian framework, where the posterior distribution (probability distribution of the true velocity, given the PIV measurements) is obtained from the prior distribution (prior...conference paper 2015
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Zoppini, G. (author), Ragni, D. (author), Kotsonis, M. (author)The application of an isolated roughness element in the laminar boundary layer developing on the surface of a wing, introduces flow instabilities that eventually lead to the breakdown of the laminar flow structures and the formation of a turbulent wedge. The present work, investigates the instabilities and transition process initiated by an...conference paper 2022
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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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Teruna, C. (author), Rego, Leandro (author), Casalino, D. (author), Ragni, D. (author), Avallone, F. (author)High-fidelity numerical simulations have been performed to investigate the noise reduction capability of porous leading-edge treatments for mitigating rotor-stator interaction noise in a full-scale aircraft model. The aircraft model consists of the NASA High-Lift Common Research Model (HL-CRM) airframe combined with an up-scaled Source...conference paper 2022
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Zamponi, R. (author), Avallone, F. (author), Ragni, D. (author), van der Zwaag, S. (author)Coating a circular cylinder with porous materials constitutes an effective passive strategy for reducing the flow-induced noise linked to the vortex shedding. Despite the number of investigations in the last decade, the noise-mitigation mechanisms associated with this technique remain unclear. The present research aims to clarify the role played...conference paper 2022
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Vergés i Plaza, G. (author), Fischer, Andreas (author), Lylloff, Oliver (author), Bak, Christian (author), Olsen, Anders S. (author), Luesutthiviboon, S. (author), Lima Pereira, L.T. (author), Ragni, D. (author), Avallone, F. (author)An experimental aero-acoustic characterisation of the NACA 63 <sub>3</sub>-018 airfoil is presented in this study, featuring trailing-edge noise emissions with and without serrations. Measurements have been carried out for a chord-based Reynolds number range between 0.18 × 10 <sup>6</sup> and 4.8 × 10 <sup>6</sup> . Two airfoil models with...conference paper 2022
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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)The application of a porous coating to a cylinder can significantly reduce the vortex shedding tone when placed in a uniform flow. The mechanism of how this porous media attenuates vortex shedding has been studied more in recent years yet it is still not fully understood. Typical porous materials within a certain range of porosity and airflow...conference paper 2022
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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)The present study reports a novel wavelet-based method aimed at separating the noise emitted by a single propeller into two contributions, tonal and broadband. An assessment using two different experimental investigations of propellers operating in diverse configurations is presented. The first experiment focuses upon near-field polar microphone...conference paper 2022
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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