- document
-
Sinnige, T. (author), Ragni, D. (author), Malgoezar, A.M.N. (author), Eitelberg, G. (author), Veldhuis, L.L.M. (author)Advanced propellers promise significant fuel-burn savings compared to turbofans. When installed on the fuselage in a pusher configuration, the propeller interacts with the wake of the supporting pylon. This paper presents an experimental analysis of the aerodynamic and aeroacoustic characteristics of this pylon–propeller interaction. An isolated...journal article 2017
- document
-
Arce Leon, C.A. (author), Merino Martinez, R. (author), Pröbsting, S. (author), Ragni, D. (author), Avallone, F. (author)The trailing edge of a NACA 0018 airfoil is modified through the attachment of serrations with different degrees of permeability. Acoustic beamforming is used to inspect the turbulent boundary layer-trailing edge noise emissions from the unmodified and serrated trailing edges. Different freestream velocities and angles of attack are investigated...journal article 2017
- document
-
de Vries, R. (author), Sinnige, T. (author), della Corte, B. (author), Avallone, F. (author), Ragni, D. (author), Eitelberg, G. (author), Veldhuis, L.L.M. (author)<br/>conference paper 2017
- document
-
della Corte, B. (author), Sinnige, T. (author), de Vries, R. (author), Avallone, F. (author), Ragni, D. (author), Eitelberg, G. (author), Veldhuis, L.L.M. (author)<br/>conference paper 2017
- document
-
van der Velden, W.C.P. (author), Avallone, F. (author), Ragni, D. (author)The relation between the far-field noise and the flow field, in presence of serrated and combed-serrated trailing edge, is studied to explain the associated noise reduction mechanisms. Both serration geometries are retrofitted to a NACA 0018 wing. Computations are carried out by solving the fully explicit, transient, compressible Lattice...conference paper 2017
- document
-
Avallone, F. (author), van der Velden, W.C.P. (author), Ragni, D. (author)Far-field noise and flow field over a novel curved trailing-edge serration (named as iron-shaped serration) are investigated. Spectra of the far-field broadband noise, directivity plots and the flow-field over the iron-shaped serration are obtained from numerical computations performed using a compressible Lattice-Boltzmann solver. The new...journal article 2017
- document
- Avallone, F. (author), van der Velden, W.C.P. (author), Merino Martinez, R. (author), Ragni, D. (author) conference paper 2017
- document
-
Ragni, D. (author), Avallone, F. (author), van der Velden, W.C.P. (author)The far-field noise and flow field of a novel curved trailing-edge serration (i.e. iron-shaped) are investigated. Spectra of the far-field broadband noise, directivity plots and the flow-field over the iron-shaped serration are obtained from numerical computations performed using a compressible Lattice-Boltzmann solver. The new design is...conference paper 2017
- document
- Merino Martinez, R. (author), Rubio Carpio, A. (author), Avallone, F. (author), Ragni, D. (author), Snellen, M. (author), van der Zwaag, S. (author) conference paper 2017
- document
-
Gamme, S. (author), De Oliveira Andrade, G.L. (author), Ragni, D. (author), Lau, F. (author)A fast, linear scaling vortex method is presented to study inviscid incompressible flow problems involving one or more actuator disks. Building upon previous efforts that were limited to axi-symmetric flow cases, the proposed methodology is able to handle arbitrary configurations with no symmetry constraints. Applications include the conceptual...conference paper 2017
- document
-
Ragni, D. (author), Ferreira, Carlos (author)A 3D stall-cell flow-field has been studied in a 4.8 aspect-ratio wing obtained by linear extrusion of a laminar NACA64-418 airfoil profile. The span-wise change in the velocity and pressure distribution along the wing has been quantified with respect to the development of cellular structures from 8◦ to 20◦ angle of attack. Oil-flow...journal article 2017
- document
- Li, Q. (author), Öztürk, K. (author), Ragni, D. (author), Sinnige, T. (author), Eitelberg, G. (author), Veldhuis, L.L.M. (author), Yangang, Wang (author) conference paper 2017
- document
-
Arce Leon, C.A. (author), Merino Martinez, R. (author), Ragni, D. (author), Pröbsting, S. (author), Avallone, F. (author), Singh, A. (author), Madsen, Jesper (author)Trailing edge serrations have been proven to work as a passive noise reduction device. Nevertheless, they have also previously been found to increase noise in a particular frequency range, argued in earlier research to be due to the misalignment of the serrations with the direction of the flow in the wake. It emerges as a high-frequency noise...conference paper 2017
- document
-
Merino Martinez, R. (author), van der Velden, W.C.P. (author), Avallone, F. (author), Ragni, D. (author)Trailing-edge serrations are passive noise reduction add-ons widely used in wind-turbine applications. This study presents acoustic beamforming results of microphone array measurements of a cambered airfoil (DU96-W-180) in a closed-section wind-tunnel at a Reynolds number of industrial interest. Two different serration geometries with different...conference paper 2017
- document
-
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
- document
-
Lignarolo, L. (author), Ragni, D. (author), Simao Ferreira, C.J. (author), Van Bussel, G.J.W. (author)The actuator disc (AD) model is commonly used to simplify the simulation of horizontal-axis wind-turbine aerodynamics. The limitations of this approach in reproducing the wake losses in wind farm simulations have been proven by a previous research. The present study is aimed at providing an experimental analysis of the near-wake turbulent flow...journal article 2016
- document
-
Caridi, Giuseppe Carlo Alp (author), Ragni, D. (author), Sciacchitano, A. (author), Scarano, F. (author)A new system for large-scale tomographic particle image velocimetry in low-speed wind tunnels is presented. The system relies upon the use of sub-millimetre helium-filled soap bubbles as flow tracers, which scatter light with intensity several orders of magnitude higher than micron-sized droplets. With respect to a single bubble generator,...journal article 2016
- document
-
Azijli, I. (author), Sciacchitano, A. (author), Ragni, D. (author), Palha, A. (author), Dwight, R.P. (author)A methodology for a posteriori uncertainty quantification of pressure data retrieved from particle image velocimetry (PIV) is proposed. 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 knowledge of...journal article 2016
- document
-
Baldacchino, D. (author), Ferreira, Carlos (author), Ragni, D. (author), van Bussel, G.J.W. (author)In this work, we present a simple inviscid point vortex model to study the dynamics of asymmetric vortex rows, as might appear behind misaligned vortex generator vanes. Starting from the existing solution of the in_nite vortex cascade, a numerical model of four base-vortices is chosen to represent two primary counter-rotating vortex pairs and...journal article 2016
- document
-
Arce Leon, C.A. (author), Merino Martinez, R. (author), Ragni, D. (author), Avallone, F. (author), Snellen, M. (author)Trailing edge serrations designed to reduce airfoil self-noise are retrofitted on a NACA 0018 airfoil. An investigation of the boundary layer flow statistical properties is performed using time-resolved stereoscopic PIV. Three streamwise locations over the edge of the serrations are compared. An analysis of the results indicates that, while...journal article 2016