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Bilan de masse et optimisation d'une structure d'aile haubanée
No full textInternational audienceThis paper focuses on the study and optimization of a strut-braced wing structure with high aspect ratio. This study is part of the Clean Aviation SMR ACAP project whose requirements will be presented. The model approach and the optimization tool will be introduced. Various optimization factors have been studied, the main one being the spanwise position of the junction between the strut and the wing. The results show that the optimum position would be located where about 60% of the lift forces are applied. These results are then contextualized and discussed.Cet article traite d'un outil d'évaluation de la masse d'une structure d'aéronef qui utilise des modèles semi-empiriques et numériques. Il vise à être intégré dans un processus multidisciplinaire d'analyse et d'optimisation de la conception (MDAO) pour les aéronefs innovants. La méthode d'optimisation est présentée et un exemple de structure d'aile haubanée est détaillé
Effect of Humidity on the Ionic Wind and the Ozone Produced by a DC Positive Corona Discharge: Numerical Simulations and Experimental Validation
No full textInternational audienceThe present study is dedicated to the 2D steady state simulation of the ionic wind and the ozone produced by a DC corona discharge between two parallel wires in ambient humid air at atmospheric pressure. The kinetic model includes a mechanism of humid air chemistry to simulate the spatial production of ozone and charged species. The model also predicts the ionic wind velocity, in dry and humid air. The results of the 2D simulations conducted with the model are compared with measurements. In humid air, H3O + (H2O)n ions are identified as the dominant ions, as opposed to O4 + ions in pure dry air. A significant reduction of the ozone production rate is observed as the humidity increases, accompanied by a slight decrease in the velocity of the ionic wind
Une correction de tête de pale de Glauert genéralisée pour les simulations stationnaires par termes sources de configurations d'hélices installées
No full textInternational audienceThe use of body-force models for propeller and turbomachinery modeling is gaining in popularity in the aerospace industry to reduce the costs of studying interactions between engines and airframes. These methods use computational fluid dynamics (CFD) to compute the flowfields and model the rotors using actuator disks, which are accounted for in the computations through source terms in the Reynolds-averaged Navier–Stokes (RANS) equations. A way to compute the disk loads is to use the blade element theory (BET), for which the local velocities are directly extracted from the CFD RANS computation. This model smears the propeller loads in the tangential direction, so it only computes the time-averaged flowfield. As a result, no tip vortices are modeled, and their absence must be compensated for in the BET computation. This problem was initially encountered for the blade element momentum theory (BEMT) [1], for which many tip-loss corrections have been developed [1–4]. Yet, the correct way to apply the tip-loss factors in RANS/BET couplings is not straightforward. Some suggestions have been made to adapt the BEMT corrections to body-force computations, either by correcting the sampled induced velocities [5] or by applying a correction factor to the loads directly [6]. Pantel et al. [7] showed that the correction of the induced velocities is more physical and should not be completely replaced by a load correction. However, whereas the BEMT directly solves for the induction factors and applies the tip correction directly to these induction factors, in RANS/BET couplings it is the velocity fields that are computed. As a result, the induction factors must be evaluated from the CFD fields to then apply the correction. This has been done by Shen et al. [5] for wind turbines in axial flows by adapting the Glauert’s correction from the BEMT. However, in nonuniform flow, the induction factors cannot be immediately obtained, and the correction should be adapted. The aim of this Note is to show that the original formulation of Shen et al. should be adapted for nonuniform conditions, even for weak perturbation fields, and to propose a more general formulation. The generalized correction is validated on a propeller in incidence and on a propeller installed in front of a wing
PISTIL, moyen de métrologie pour les surfaces d’onde segmentées
No full textInternational audienceL’interférométrie PISTIL, dédiée à la mesure de surfaces d’onde segmentées régulières issues des miroirs segmentés ou des lasers à combinaison cohérente, a évolué vers un nouveau dispositif plus compact et plus efficace, prêt pour une évolution vers un produit plug and play adapté à ce type de surfaces
Remote sensing of evaporating gases from chemical spills at sea using multispectral thermal infrared camera
No full textInternational audienceThe SIMAGAZ gas monitoring camera was deployed during the IPOMAC and MANIFEST campaigns in 2021 and 2022. These measurement campaigns were carried out several miles off the west coast of France as part of the response to pollution at sea. Various chemicals, legally classified as HNS (Hazardous Noxious Substances), were released on the sea surface and SIMAGAZ measurements were made from the ship and by air. The camera data processing is based on a physical radiometric model, a spectroscopic database containing the compounds of interest and includes a morphological analysis of the images. SIMAGAZ has thus enabled the detection, identification and quantification of several gases evaporating from spilled slicks (acetone, butyl acetate, propyl acetate, MTBE and heptane), sometimes for over half an hour. For other products with absorption lines outside the SIMAGAZ spectral range, no gas was seen as expected. On the basis of this success, the analysis of the concentration fields obtained and their dynamics can be compared with the results of evaporation and atmospheric dispersion modelling tools for HNS
Étude du comportement d'interface d'une barrière environnementale sur composite à matrice céramique
No full textOne of the challenges in aeronautics is to reduce the environmental impact of airplanes. This objective is pursued through the development of alternative solutions to metallic materials such as ceramic matrix composites. For the intended applications, the components are exposed to extremely severe thermomechanical and physicochemical environments (oxidation/corrosion), which can lead to material degradation and limit their lifespan. To protect the ceramic matrix composite (CMC), the components are coated with environmental barrier coatings (EBC) that mitigate the corrosion of the CMC. Understanding the damage mechanisms of EBC on CMC is therefore crucial for the development of carbide-based CMC components.In this context, this thesis focused on the behavior at the interfaces of the different constituents of the system to analyze the adhesion of the coating on the CMC. The aim is, on the one hand, to propose and implement tests at ambient and high temperatures to quantify the initiation and propagation of delamination at the interfaces and to characterize the associated properties, such as the adhesion energy of the coating on the CMC, using various experimental crack-tracking methods based on optical techniques. On the other hand, the goal is to establish a close interaction between the tests and the associated modeling. For this purpose, four-point bending tests were conducted at room temperature and at 1000°C to propagate stable cracks at the interface of the system. Kinematic field measurements through image correlation were used to inform finite element simulations in order to track crack propagation and extract interfacial adhesion energy at the macroscopic scale. These tests and their analysis were used to characterize the propagation phase at both temperatures and to compare the adhesion of pristine systems with systems that had been previously aged in an oxidizing environment. In a second phase, laser bench tests with the presence of thermal gradients within the system allowed for the characterization of the initiation phase. Scanning electron microscope observations, along with the use of thermal cameras and acoustic emission sensors, complemented the experimental database.Un des enjeux de l'aéronautique est de réduire l'impact environnemental des avions. Cet objectif se traduit par le développement de solutions alternatives aux matériaux métalliques comme les composites à matrice céramique. Pour les applications visées, les pièces sont soumises à des environnements thermomécaniques et physico-chimiques (oxydation/corrosion) très sévères pouvant mener à la dégradation du matériau et à une limitation de sa durée de vie. Pour protéger le composite à matrice céramique (CMC), les pièces sont revêtues de barrières environnementales (EBC) qui limitent la corrosion du CMC. La compréhension des mécanismes d'endommagement des EBC sur CMC est donc cruciale pour le développement des pièces en CMC à base carbure.Dans ce contexte, cette thèse s'est focalisée sur le comportement aux interfaces des différents constituants du système pour analyser la tenue du revêtement sur CMC. Il s'agit ainsi, d'une part, de proposer et de mettre en place des essais à l'ambiante et à haute température pour quantifier l'amorçage et la propagation de décohésions aux interfaces et de caractériser les propriétés associées, telles que l'énergie d'adhérence du revêtement sur le CMC, en utilisant différentes méthodes expérimentales de suivi de fissuration par méthodes optiques. D'autre part, le but est de proposer un dialogue étroit entre les essais et les modélisations associées. Pour cela des essais de flexion 4 points ont été menés à température ambiante et à 1000°C afin de faire propager des fissures stables à l'interface du système. Des mesures de champs cinématiques par corrélation d'images ont permis d'alimenter des simulations éléments finis afin de suivre la propagation des fissures et d'extraire une énergie d'adhérence interfaciale à l'échelle macroscopique. Ces essais et leur exploitation ont servi à caractériser la phase de propagation pour les deux températures et de comparer l'adhérence de systèmes sains et de systèmes préalablement vieillis sous environnement oxydant. Dans un deuxième temps, des essais au banc laser avec la présence de gradients thermiques au sein du système ont permis de caractériser la phase d'amorçage. Des observations au microscope électronique à balayage, l'utilisation de caméras thermiques et de capteurs d'émission acoustique sont venus compléter la base de données expérimentales
Estimation of Urban Tree Chlorophyll Content and Leaf Area Index Using Sentinel-2 Images and 3D Radiative Transfer Model Inversion
No full textInternational audienceUrban trees play an important role in mitigating effects of climate change and provide essential ecosystem services. However, the urban environment can stress trees, requiring the use of effective monitoring methods to assess their health and functionality. The objective of this study, which focused on four deciduous tree species in Rennes, France, was to evaluate the ability of hybrid inversion models to estimate leaf chlorophyll content (LCC), leaf area index (LAI), and canopy chlorophyll content (CCC) of urban trees using eight Sentinel-2 (S2) images acquired in 2021. Simulations were performed using the 3D radiative transfer model DART, and the hybrid inversion models were developed using machine-learning regression algorithms (random forest (RF) and gaussian process regression). Model performance was assessed using in situ measurements, and relations between satellite data and in situ measurements were investigated using spatial allocation (SA) methods at the pixel and tree scales. The influence of including environment features (EFs) as model inputs was also assessed. The results indicated that random forest models that included EFs and used the pixel-scale SA method were the most accurate with R 2 values of 0.33, 0.29, and 0.46 for LCC, LAI, and CCC, respectively, with notable variability among species
Goal modelling in aeronautics: Practical applications for aircraft and manufacturing designs
No full textInternational audienceTraditional aircraft development follows a sequential approach: the aircraft is designed first, followed by the industrial system. This approach limits the industrial system’s performance due to constraints imposed by the pre-defined aircraft design. Collaborative approaches, however, advocate for simultaneous design of different products to create new opportunities. Within a project focused on co-designing aircraft and their industrial systems, we put goal modelling into practice to gain a comprehensive understanding of the objectives driving each system’s design and their interdependencies. The intention was to develop an approach for actively involving domain experts, even those lacking prior knowledge of Goal-Oriented Requirements Engineering (GORE).This paper provides a detailed account of the iterative process employed to develop and refine our approach. For each iteration, we describe the organisation of modelling sessions with experts, the resulting models, and the collected feedback. We also report on the overall approach’s reception from both industry experts and academic participants. Furthermore, we highlight recommendations and research challenges that emerged from the encountered difficulties during the iterative process, suggesting avenues for further investigation and improvement
Extension of Fitts’ definition of Index of Difficulty to slalom passing task with identification of speed and accuracy terms
No full textInternational audienceWhen asserting Handling Qualities, identifying objective quantities to measure circumstantial difficulty is crucial to discriminate surroundings complexity from control dynamics inner intricacy. On a task of slalom, Fitts’ Index of Difficulty (ID) is particularly appropriate as it solely captures obstacle gate geometry. If it gradually benefited from an extension to goal passing tasks in 2D, setup mostly consists in direct control and egocentric displays. Yet, considering ecological conditions is pivotal when extrapolating to piloting as visual display is a central feedback modality and flight dynamics significantly impact task complexity. This work thus proposes to reassess Fitts’ paradigm in more ecological scenarios, using Accot’s goal passing task: 21 gates of width W longitudinally spaced at a distance L andalternatively laterally offset by ±H/2 to be passed under a speed/accuracy trade-off. We aim to redefine the relation between movement time T and ID when manipulating each axis independently. Indeed, if it is straight-forward that increase in hypotenusal, gate-to-gate distance D =√H2 + L2 results in prolonged T, only lateral displacement adheres to the back-and-forth pattern characteristic of Fitts’paradigm. Therefore, the core idea is to discriminate the impact of L versus H on T. To this extent, 5 (H; L) pairs covering one set of increasing H and one of increasing L are tested against two control modes (position and velocity) in a simulated flight environment that aims to replicate ecologicalscenarios, mirroring the velocity range and intermediate flight dynamics in urban-themed visuals from an egocentric perspective. Even though this is a work in progress, we expect to exploit dependency to longitudinal axis to secern speed vs accuracy terms in T = T(L) + T(H). With this approach, we seekto pave the way for wider application of the slalom task as defined in Aeronautical Design Standard -33 (ADS-33) through a nuanced examination of Fitts’ law
Récentes activités sur la FA métallique pour l'aéronautique
No full textInternational audienceThis article brings together a number of activities of the last three years carried out at ONERA in the Materials and Structures Department (DMAS) on metal additive manufacturing (AM). The materials concerned are those found in aircraft structures and engines, namely aluminum alloys, titanium alloys and superalloys.Le présent article rassemble un certain nombre des activités des trois dernières années effectuées à l'ONERA au département Matériaux et Structures (DMAS) sur la fabrication additive (FA) métallique. Les matériaux concernés sont ceux que l'on rencontre dans les structures et les moteurs d'avions, en l'occurrence les alliages d'aluminium, de titane et les superalliages