Experimental investigation of low Reynolds number rotor noise

In this paper, an experimental characterisation of low Reynolds number rotors is performed in an anechoic room. Two commercially available two-bladed rotors as well as four three-dimensional (3D)-printed rotors with different numbers of blades (from two to five) are tested. The latter have canonical geometry, with an NACA0012 blade section profile, extruded in the radial direction with constant chord and constant 10° pitch. The experimental setup and the 3D printing strategy are first validated using results from the literature for the commercially available rotors. For all the tested rotors, four noise characteristics are analysed: the overall sound pressure level (OASPL), the amplitude of the blade passing frequency (BPF), and the amplitude of its first harmonic and the high-frequency broadband noise. For all the rotors, an increase in all noise characteristics is observed with the rotational speed (rpm) for all directivity angles. Moreover, an interesting change of pattern is observed for the amplitudes of the BPF and of its first harmonic, with, in the vicinity of the rotor plane, a minimum value for low rpm and/or high number of blades, and a maximum value for high rpm and/or low number of blades. This change in directivity leads to a similar change of directivity of the OASPL. For the broadband noise, a dipole-like pattern is obtained with a minimum value at h ¼ �10°, i.e., aligned with the trailing edge and thus indicating the generation of trailing edge noise. Finally, scaling laws that characterise the amplitude of the different noise components with respect to the rpm are proposed

Application de l'holographie acoustique en soufflerie par mesures LDV

L Holographie acoustique de champ proche (NAH) est une méthode d imagerie acoustique robuste, mais son application en écoulement peut être limitée par l utilisation de mesures intrusives de pression ou de vitesse acoustique. Dans cette étude, une procédure holographique applicable en écoulement utilisant des mesures de vitesse non-intrusives est proposée. Cette méthode est basée sur le théorème intégral de Kirchhoff-Helmholtz convecté. La fonction de Green convectée est alors utilisée pour déterminer des propagateurs spatiaux convectés définis dans l espace réel et incluant l effet d un écoulement subsonique uniforme. Les transformées de Fourier discrètes de ces propagateurs permettent alors d évaluer les champs acoustiques à partir de la mesure du champ de pression ou de vitesse acoustique normale. Le but étant de développer une méthode de caractérisation de sources aéroacoustiques à partir de mesures de vitesse non-intrusives, cette étude se concentre essentiellement sur les propagateurs réels convectés basés sur la mesure de vitesse acoustique. Afin de valider cette procédure,des simulations ont été menées dans le cas de combinaisons de sources monopolaires et dipolaires convectées corrélées ou non. La procédure holographique développée donne de bons résultats par comparaison aux champs acoustiques théoriques. Une comparaison des résultats obtenus par les propagateurs convectés réels, développés dans cette thèse, avec ceux obtenus par leurs formes spectrales, développés par Kwon et al. fin 2010 pour des mesures de pression acoustique, montre l intérêt d utiliser la forme réelle pour la reconstruction de la pression acoustique à partir de la mesure de vitesse acoustique normale. L efficacité de la procédure développée est confirmée par une campagne de mesure en soufflerie avec un haut-parleur affleurant rayonnant au sein d un écoulement à Mach 0.22, et des mesures non-intrusives effectuées par Vélocimétrie Laser Doppler (LDV). Les champs de vitesse acoustique utilisés pour la procédure holographique sont dans ce cas extraits des mesures LDV par corrélation avec un microphone de référence. La faisabilité de prendre en compte des variations de l écoulement dans la direction de reconstruction holographique est également vérifiée.Nearfield Acoustic Holography (NAH) is a powerful acoustic imaging method but its application in flow can be limited by intrusive measurements of acoustic pressure or velocity. In this work, a moving fluid medium NAH procedure using non-intrusive velocity measurements is proposed. This method is based on the convective Kirchhoff-Helmholtz integral formula. The convective Green s function is then used to derive convective realspace propagators including uniform subsonic airflow effects. Discrete Fourier transforms of these propagators allow then the assessment of acoustic fields from acoustic pressure or normal acoustic velocity measurements. As the aim is to derive an aeroacoustic sources characterisation method from non-inrusive velocity measurements, this study is especially focused on real convective velocity-based propagators. In order to validate this procedure, simulations in the case of combinations of monopolar and dipolar sources correlated or not, radiating invarious uniform subsonic flows, have been performed. NAH provides very favorable results when compared to the theoretical fields. A comparison of results obtained by real convective propagators, developed in this work, and those obtained by the spectral ones, developed by Kwon et al. at the end of 2010 for acoustic pressure measurements, shows the interest of using the real-form for NAH acoustic pressure reconstruction from normal acoustic velocity measurements. The efficiency of the developed procedure is confirmed by a wind tunnel campaign with a flush-mounted loudspeaker radiating in a flow at Mach 0.22 and non-intrusive Laser Doppler Velocimetry (LDV) measurements. Acoustic velocity fields used for the NAH procedure are in this case extracted from LDV measurements by correlation with a reference microphone. The feasibility of taking into account mean flow variations in the direction of NAH reconstruction is also checked.TOULOUSE-ISAE (315552318) / SudocSudocFranceF

Use of the 3D radon transform to examine the properties of oceanic Rossby waves

One of the most successful applications of satellite-borne radar altimeter data over the oceans in recent years has been the extraction of information about long-wavelength baroclinic Rossby (or planetary) waves, which play a significant role in ocean circulation and climate dynamics. These waves cross ocean basins from east to west at speeds of few centimetres per second at mid-latitudes. The cross-basin propagation time may therefore be several months or even years and an accurate estimation of the speed of the waves is important. We review the methods for obtaining information on Rossby wave velocity from altimetry data, particularly the two-dimensional Radon transform. Unfortunately the use of longitude-time plots, although it allows the estimation of the zonal phase speeds, does not give any information on the speed vector when the propagation of the waves is not purely zonal (east-west). We show how the two-dimensional Radon Transform can be generalised to three dimensions, enabling not only the true propagation velocity component to be determined, but also the direction of the waves and thus any deviation from the pure-westward case. As examples of the application of this extended technique, we show maps of direction, speed and energy of Rossby waves in the North Atlantic Ocean

Aeroacoustic radiation of a low Reynolds number two-bladed rotor in interaction with a cylindrical beam

In this paper, a characterization of a low Reynolds number two-bladed rotor in interaction with a beam is performed using both an experimental campaign performed in an anechoic room and implicit large eddy simulations (iLES) associated with the Ffowcs-Williams and Hawkins (F-WH) analogy. The rotor studied has a NACA0012 blade section profile extruded in the radial direction with a constant chord of 25 mm, a constant pitch of 10  and a diameter of 200 mm. This rotor is tested in interaction with 3 cylindrical beams of different diameters positioned at a distance of 20 mm below the rotor disk plane. The blade passing frequency (BPF) and the high frequency broadband noise appear to not be affected by the presence of the beam. On the contrary, the magnitude of the 2 BPF to 15 BPF harmonics increases up to 30 dB compared to the case without beam. For the dominant harmonics of the BPF, a dipole like pattern aligned with the beam can be observed. Numerical simulations were successfully validated against the experimental data for the dominant BPF harmonics and were then used to study the contribution of the rotor and the beam to the noise radiated. It is found that the beam is responsible for the increase in BPF harmonics and their characteristic directivity pattern

Functional role of ɛ-tubulin in the assembly of the centriolar microtubule scaffold

Centrioles and basal bodies fascinate by their spectacular architecture, featuring an arrangement of nine microtubule triplets into an axial symmetry, whose biogenesis relies on yet elusive mechanisms. However, the recent discovery of new tubulins, such as δ-, ɛ-, or η-tubulin, could constitute a breakthrough for deciphering the assembly steps of this unconventional microtubule scaffold. Here, we report the functional analysis in vivo of ɛ-tubulin, based on gene silencing in Paramecium, which demonstrates that this protein, which localizes at the basal bodies, is essential for the assembly and anchorage of the centriolar microtubules

Prédiction de la dormance des pommes de terre pendant le stockage

Potato sprouting during storage occurs after a break in dormancy, leading to a decrease in quality and consequently economic losses. We used 3379 records from multi-year and multi-environment trials of 537 potato varieties to identify the main factors driving potato dormancy and to develop predictive models for an efficient sprouting forecast. The variety explained the majority of the dormancy variability (60.3%), followed by the year (13.9%) and the location (5.4%). About 250 predictors were considered to develop a predictive model of potato dormancy. The selected model had a validation precision of 14.59 days; it used the variety class and the sum of the daily maximum temperatures in the air during the period from planting to harvest as predictors. The predictions of the selected model were supported by results of the in vivo trial using dormancy measurements from potato varieties grown under different temperature regimes in greenhouse conditions. With the growing impact of climate change on crop production, predictive models as developed here can provide an efficient and cost-effective tool to optimize the control of potato sprouting during storage.2. Zero hunge

SETHI / RAMSES-NG: New performances of the flexible multi-spectral airborne remote sensing research platform

International audienceSETHI is an airborne SAR/GMTI system developed by the French Aerospace Lab. ONERA, and integrating various sensors. In 2016 ONERA invested in upgrade and improvement of all SETHI components. The microwave ones cover from VHF-UHF to X Band, full polarimetric and very high resolution, along track and cross track interferometry and very high precision multi-baseline capacity for interferometry and tomography applications. The optronic sensors offer very high spatial resolution visible images and fine spectral scene analysis in VNIR and SWIR bands. This paper presents the upgrade and new performances of this flexible platform and the qualification campaign results with various sensor configurations

Aerodynamic and Aeroacoustic Study of Low Reynolds Number Rotors: Influence of Pitch Angle, Airfoil Camber and Thickness

With the increase in the use of micro air vehicles (MAVs), the issue of noise pollution is becoming critical in both military and civilian fields. The main noise component in quadcopter MAVs is generated by the rotors and their interactions with the whole body. Here, a Non-Linear Vortex Lattice/Particle Method (NVLM), coupled with the Farassat formulation-1A of the Ffowcs-Williams and Hawkings (FW-H) acoustic analogy, is used to characterize the influence of the blade pitch and the airfoil shape on the tonal noise and the aerodynamic performance of low Reynolds number rotors typical of MAVs. The validation of both NVLM and FW-H codes is adressed with test cases from the literature and experiments on a 25cm diameter NACA0012 constant-pitch rotor in hovering conditions. The tonal noise of this MAV rotor is then studied in details. Finally, a parametric study of rotor pitch angle and of airfoil camber and thickness is performed, providing guidelines for the design of small rotors with low acoustic footprint and optimal aerodynamic performance

1H-NMR-Based Metabolomic Profiling of CSF in Early Amyotrophic Lateral Sclerosis

Background: Pathophysiological mechanisms involved in amyotrophic lateral sclerosis (ALS) are complex and none has identified reliable markers useful in routine patient evaluation. The aim of this study was to analyze the CSF of patients with ALS by 1 H NMR (Nuclear Magnetic Resonance) spectroscopy in order to identify biomarkers in the early stages of the disease, and to evaluate the biochemical factors involved in ALS. Methodology: CSF samples were collected from patients with ALS at the time of diagnosis and from patients without neurodegenerative diseases. One and two-dimensional 1 H NMR analyses were performed and metabolites were quantified by the ERETIC method. We compared the concentrations of CSF metabolites between both groups. Finally, we performed principal component (PCA) and discriminant analyses. Principal Findings: Fifty CSF samples from ALS patients and 44 from controls were analyzed. We quantified 17 metabolites including amino-acids, organic acids, and ketone bodies. Quantitative analysis revealed significantly lower acetate concentrations (p = 0.0002) in ALS patients compared to controls. Concentration of acetone trended higher (p = 0.015), and those of pyruvate (p = 0.002) and ascorbate (p = 0.003) were higher in the ALS group. PCA demonstrated that the pattern of analyzed metabolites discriminated between groups. Discriminant analysis using an algorithm of 17 metabolites reveale