1,721,010 research outputs found
Dataset corresponding to the publication : Aeroacoustic radiation of low Reynolds number rotors in interaction with beams, Gojon et al., JASA, 2023.
No full textRotor interacting with a beam noise database as presented in Gojon, Parisot-Dupuis, Mellot, & Jardin. Aeroacoustic radiation of low Reynolds number rotors in interaction with beams. JASA, 2023. Thrust and power coefficients, as well as autopower of acoustic pressure are given. The name gives the operating point, for example, in the files ISAE_2_D10_L20_autopower and ISAE_2_D10_L20_static, D stands for the circular geometry of the cylinder beam, 10 its diameter (in mm), and L the distance between the beam and the rotor disk plane (in mm).
CAD files of the three rotors (ISAE 2, ISAE 3, and ISAE 4) are also provided
Example matlab codes to post-process results can also be found :
- For aerodynamic results , the thrust and power coefficients are given as a function of RPM. Typical temperature and fluid density values are 290K and 1.2kg/m3, respectively. In some cases, data exhibit relatively low values at a given RPM compared to those at other RPMs (e.g. ISAE_2_T10_L20_static at 7000 RPM), which might be due to vibrations of the test rig at this RPM.
- For acoustic results, the autopower (Pa2) is given as a function of the frequency (Hz). Autopowers are obtained from fluctuating pressure time signals (16s) by computing the fast Fourier transform (FFT) with a Hanning window applied on 100 segments, using a 50% overlap and a magnitude correction factor, which leads to a frequency resolution of 3.125 Hz.
Structure of acoustic data :
For each rotation speed, data from 13 microphones located 1.62m away from the rotor center and at different latitude angles (every 10 degrees) from the rotor plane are provided. Microphone 1 corresponds to +60 degrees (with respect to the rotor plane, where + indicates that it is located in the direction opposite of the flow, for our rotors blowing downward, please refer to Figure 1 from the publication). Microphone 2 corresponds to +50 degrees ... Microphone 7 corresponds to 0 degrees (the rotor plane) … Microphone 13 corresponds to -60 degrees. Moreover, the test rig is fixed on a turntable, which can rotate the entire rotor-beam setup in azimuth with a step angle of 10 degrees. With the couple directivity antenna/turntable, the almost complete spherical directivity can be investigated, only the poles (absolute value of latitude angle over 60 degrees) being missing. The definitions of latitude and azimuth angles are given in Figure 1 of the corresponding publication.<br
Dataset corresponding to the publication : Serration Manufacturing Effects on Propeller Trailing Edge Noise Mechanisms, Santamaria et al., JSV, 2026.
No full textRotors with trailing edge serrations as presented in Santamaria, Belliot, Sanjosé, Gojon, and Moreau. Serration Manufacturing Effects on Propeller Trailing Edge Noise Mechanisms. Journal of Sound and Vibrations, 2026.
Thrust and torque coefficients, Figure of Merit, as well as acoustic autopower signals are provided.
CAD files of the serrated and clean rotors, as well as example Matlab code to post-process acoustic results are also given.
For aerodynamic results, the thrust and torque coefficients are given as a function of RPM. Fluid density is taken as 1.18kg/m3.
For acoustic results, the autopower (Pa2) is given as a function of the frequency (Hz). Autopowers are obtained from fluctuating pressure time signals (16s) by computing the fast Fourier transform (FFT) with a Hanning window applied on 100 segments, using a 50% overlap and a magnitude correction factor, which leads to a frequency resolution of 3.125 Hz.
Structure of the acoustic data
For each rotation speed, data for 13 microphones located 1.62m away from the rotor axis and at different angles (every 10 degrees) from the rotor plane are provided.
Microphone 1 corresponds to +60 degrees (as compared with the rotor plane, where + indicates that it is located in the direction opposite of the flow, as visible in Figure 5 of the corresponding journal paper)
Microphone 2 corresponds to +50 degrees
...
Microphone 7 corresponds to 0 degrees (the rotor disk plane)
...
Microphone 13 corresponds to -60 degrees<br
Large Eddy Simulations for Indirect Combustion Noise Assessment in a Nozzle Guide Vane Passage
Full text linkThe combustion noise in aero-engines is known to originate from two different sources. First, the unsteady heat release in the combustion chamber generates the direct combustion noise. Second, hot and cold spots of air generated by the combustion process are convected and accelerated by the turbine stages and give rise to the so-called indirect combustion noise. The present work targets, by using a numerical approach, the generation mechanism of indirect combustion noise for a simplified geometry of a turbine stator passage. Periodic temperature fluctuations are imposed at the inlet, permitting to simulate hot and cold packets of air coming from the unsteady combustion. Three-dimensional Large Eddy Simulation (LES) calculations are conducted for transonic operating conditions to evaluate the blade acoustic response to the forced temperature perturbations at the inlet plane. Transonic conditions are characterized by trailing edge expansion waves and shocks. It is notably shown that their movement can be excited if disturbances with a particular frequency are injected
in the domain
Computational Analysis of the Indirect Combustion Noise Generation Mechanism in a Nozzle Guided Vane in Transonic Operating Conditions
Full text linkThe combustion noise in modern engines is mainly originating from two types of mechanisms. First, chemical reactions in the combustion chamber leads to an unsteady heat release which is responsible of the direct combustion noise. Second, hot and cold blobs of air coming from the combustion chamber are advected and accelerated through turbine stages, giving rise to entropy noise (or indirect combustion noise). In the present work, numerical characterization of indirect combustion noise of a Nozzle Guide Vane passage was assessed
using three-dimensional Large Eddy Simulations. The present work offers an overview to the analytical, computational and experimental studies of the topic. Numerical simulations are conducted to reproduce the effects of incoming planar entropy waves from the combustion chamber and to characterize the generated acoustic power. The dynamic features of the flow are addressed by the means of frequency domain and modal analyses techniques such as Fourier Decomposition and Proper Orthogonal Decomposition. Finally,
the predicted entropy noise from numerical calculations is compared with the analytical results of an actuator
disk model for a stator stage. The present paper proves that the generated indirect combustion noise can be
significant for transonic operating conditions. The blade acoustic response is characterized by the excitation
of a latent dynamics at the forcing frequency of the planar entropy waves, and it increases as the amplitude of the incoming disturbances increases
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Validation of an LBM solver for the aerodynamic and aeroacoustic study of a propeller
No full textLAUREA MAGISTRALEIl dipartimento di aerodinamica e propulsione (DAEP) dell'ISAE-Supaéro sta attualmente studiando l'aeroacustica dei MAV (Micro Air Vehicles), concentrandosi principalmente sui loro rotori e sulle potenziali interazioni per ridurre le emissioni di rumore. L'obiettivo a lungo termine è quello di proporre forme e cinematiche innovative del rotore per ridurne il rumore massimizzando l'efficienza aerodinamica. Attualmente viene condotta una campagna sperimentale nella camera anecoica dell'ISAE-Supaéro, dove vengono testate diverse forme di rotore. In particolare, viene registrato il rumore emesso dal rotore e vengono misurate le forze aerodinamiche. Il presente lavoro di tesi si concentra sulla convalida di un risolutore basato su modelli Lattice-Boltzmann (LBM), contro i dati sperimentali raccolti. Il codice in question è OmnisLB, un codice industriale di Numéca, sviluppato congiuntamente dall'Università di Ginevra e dall'ISAE-Supaéro.The department of Aerodynamics and Propulsion (DAEP) at ISAE-Supaéro is currently investigating the aeroacoustic of MAV (Micro Air Vehicles), mostly focusing on their rotors and potential interactions to reduce noise emissions. The long-term objective is to propose innovative rotor shapes and kinematics to reduce their noise while maximizing the aerodynamic efficiency. This is crucial in the current context where the use of MAV in an urban environment has increased rapidly over the last decade. Currently, an experimental campaign is carried out in the anechoic chamber at ISAE-Supaéro, where several rotor shapes are tested. In particular, the noise emitted by the rotor is recorded by a near-field microphone, and the aerodynamic forces are also measured. The present thesis work focus on the validation of a high-fidelity method, called Lattice-Boltzmann Method (LBM), against this experiment. The code is OmnisLB, an industrial LBM code from Numéca, which is co-developed by University of Geneva and ISAE-Supaéro
Transonic flow features in a nozzle guide vane passage
No full textLAUREA MAGISTRALENei motori areonautici moderni, il rumore associato alla grandezza termodinamica
entropia ha origine principalmente da due meccanismi. Per prima cosa, le reazioni
chimiche all’interno della camera di combustione danno origine ad un rilascio di
un flusso di calore instazionario, il quale è responsabile della generazione del rumore
di combustione diretto. Inoltre, porzioni di aria calda e fredda provenienti
dalla camera di combustione sono accelerate attraverso i vari stadi della turbina,
dando origine al soprannominato rumore entropico (o altresí noto come rumore di
combustione indiretto). Nel presente lavoro, la caratterizzazione numerica del rumore
di combustione indiretto attraverso le pale guida dello statore di una turbina
è stata effettuata grazie all’utilizzo di simulazioni fluidodinamiche LES (Large Eddy
Simulations). Lo studio è stato condotto su una geometria semplificata di un reale
statore, per il quale erano disponibili i dati sperimentali relativi a condizioni operative
transoniche. All’inizio, un caso di riferimento è stato riprodotto mediante le
simulazioni numeriche in modo da validare un solutore ai volumi finiti attraverso
un confronto con i dati sperimentali. In seguito, lo stesso solutore è stato utilizzato
per riprodurre gli effetti di un sistema di onde di entropia provenienti dalla camera
di combustione e per caratterizzare un’eventuale generazione di potenza acustica
addizionale rispetto al caso base di riferimento. Fluttuazioni periodiche di temperatura
sono state imposte all’ingresso del dominio computazionale, permettendo
di simulare masse di aria calda e fredda derivanti dalla combustione instazionaria.
Uno studio parametrico è stato effetuato variando la lunghezza d’onda delle fluttuazioni,
tramite l’imposizione di temperature di ingresso differenti. Lo studio dimostra
che l’intensitá del rumore di combustione indiretto puó essere significativa e
puó aumentare qualora aumentino le lunghezze d’onda delle fluttuazioni. Infine, il
presente lavoro suggerisce che, in condizioni transoniche, possano esserci caratteristiche
della corrente fluidodinamica che favoriscano la generazione del rumore di
combustione indiretto.The entropy noise in modern engines is mainly originating from two types of mechanisms.
First, chemical reactions in the combustion chamber lead to unsteady heat release
which is responsible of the direct combustion noise. Second, hot and cold blobs
of air coming from the combustion chamber are advected and accelerated through
turbine stages, giving rise to the so-called entropy noise (or indirect combustion
noise). In the present work, numerical characterization of indirect combustion noise
of a Nozzle Guide Vane passage was assessed using three-dimensional Large Eddy
Simulations. The study was conducted on a simplified topology of a real turbine
stator passage, for which experimental data were available in transonic operating
conditions. First, a baseline case was reproduced to validate a numerical finite volume
solver against the experimental measurements. Then, the same solver is used to
reproduce the effects of incoming entropy waves from the combustion chamber and
to characterize the additional generated acoustic power. Periodic temperature fluctuations
are imposed at the inlet, permitting to simulate hot and cold packets of air
coming from the unsteady combustion. The incoming waves are characterized by
their characteristic wavelength; therefore, a parametric study has been conducted
varying the inlet temperature of the passage, generating entropy waves of greater
wavelengths. The study proves that the generated indirect combustion noise can
be significant. Moreover, the generated indirect combustion noise increases as the
wavelength of the incoming disturbances increases. Finally, the present work suggests
that, in transonic conditions, there might be flow features which enhance the
indirect combustion noise generation mechanism
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