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Rubio Carpio, A. (author), Avallone, F. (author), Ragni, D. (author), Snellen, M. (author), van der Zwaag, S. (author)Turbulent boundary layer trailing-edge noise scattered by a NACA0018 airfoil equipped with 3D printed perforated trailing-edge inserts, i.e. with straight cylindrical channels connecting the two sides of the airfoil, is investigated. The inserts have different permeability in order to assess the effect of this property on broadband noise...conference paper 2019
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Teruna, C. (author), Manegar, F.A. (author), Avallone, F. (author), Casalino, D. (author), Ragni, D. (author), Rubio Carpio, A. (author), Carolus, Thomas (author)This manuscript presents a numerical investigation of the turbulent boundary layer-trailing edge (TBL-TE) noise reduction with an open-cell porous material. The implementation of the porous media is verified by emulating a facility for characterizing the flow resistivity of the porous material. Subsequently, the porous media is applied on the...conference paper 2019
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Arcondoulis, Elias J. G. (author), Ragni, D. (author), Rubio Carpio, A. (author), Avallone, F. (author), Liu, Yu (author), Yang, Yannian (author), Li, Zhiyong (author)Porous coated cylinders have been shown to reduce the vortex shedding tone and broadband noise of a bare cylinder placed in uniform flow within specific Reynolds number regimes. The processes by which the vortex shedding and thus tone suppression take place are still uncertain despite numerous numerical and experimental studies. It is understood...conference paper 2019
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Ye, Q. (author), Avallone, F. (author), Ragni, D. (author), Choudhari, Meelan (author), Casalino, D. (author)Surface roughness elements are often used to force laminar to turbulent transition during aerodynamic and aeroacoustic experiments in wind tunnels. The statistical features and frequency content of the forced turbulent boundary layer can influence the far-field trailing edge noise. To study this dependence, boundary layer transition induced by...conference paper 2019
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VanDercreek, Colin (author), Sijtsma, P. (author), Snellen, M. (author), Ragni, D. (author), Avallone, F. (author), Simons, D.G. (author)A mathematical model is proposed that evaluates acoustic propagation of turbulent boundary layer waves on top of a cavity enclosing a microphone. The goal is to optimize these cavity geometries to improve the signal-to-noise ratio of acoustic measurements. This model predicts the attenuation of the turbulent boundary layer fluctuations...conference paper 2019
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Luesutthiviboon, S. (author), Avallone, F. (author), Ragni, D. (author), Snellen, M. (author)An analytical method for predicting the steady pressure distribution on porous airfoils with a prescribed porosity distribution is assessed through comparison of its lift prediction with experimental data. The method is based on the thin-airfoil formulation. The no-slip boundary condition of the airfoil surface has been replaced by the Darcy’s...conference paper 2019
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Bampanis, G. (author), Roger, M. (author), Ragni, D. (author), Avallone, F. (author), Teruna, C. (author)The present work is aimed at assessing leading-edge serrations as an airfoil turbulenceimpingement noise (TIN) reduction mean. It relies on extended anechoic wind-tunnel testing including far-field measurements over an observation sphere to infer the three-dimensional features of TIN, and on microphone-array measurements to extract leading-edge...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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González, G. (author), Ragni, D. (author), Avallone, F. (author), Schneiders, J.F.G. (author), Casalino, D. (author), Ianiro, A. (author)The analysis of the unsteady flow field of an axisymmetric subsonic jet at Reynolds numbers between 5,000 and 20,000 and computation of its unsteady pressure field is carried out from single snapshots of tomographic PIV measurements (acquisition rate 0.8 Hz). This is achieved by a recently developed pressure-evaluation technique based upon...conference paper 2018
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Rubio Carpio, A. (author), Avallone, F. (author), Ragni, D. (author)The turbulent flow over a NACA 0018 airfoil with porous trailing edge inserts and the resulting scattered turbulent-boundary-layer trailing edge noise are studied to investigate the effect of the cross-flow through the material. The experiments are performed at a chord-based Reynolds number of 2.63×10<sup>5</sup> and an angle of attack of 0°....conference paper 2018
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Manjunath, P. (author), Avallone, F. (author), Casalino, D. (author), Ragni, D. (author), Snellen, M. (author)Acoustic liners are widely used as noise suppression devices, for example in aircraft engines. The effectiveness of the liners is measured through the impedance. In the present study, using a lattice-Boltzmann solver, the response of two liner geometries to grazing acoustic waves is examined. The two geometries have porosity equal to 0.99%...conference paper 2018
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Merino Martinez, R. (author), Sanders, Martinus P.J. (author), Caldas, Luciano C. (author), Avallone, F. (author), Ragni, D. (author), de Santana, Leandro D. (author), Snellen, M. (author), Simons, D.G. (author)Microphone arrays are useful measurement devices for estimating the location and strength of sound sources. Numerous comparative studies have been conducted regarding the performance of acoustic imaging methods in the past, but literature lacks of a systematic investigation on the role of the hardware on the measurements. This research...conference paper 2018
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- 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
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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
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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
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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
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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
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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