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Impact sonore de livraison de colis par drone dans un scénario sur Madrid
No full textInternational audienceTo effectively integrate drones into densely populated urban infrastructures, it is crucial to assess their impact on the population's quality of life and mitigate any adverse effects. As noise pollution from drone overflights is a top concern, enhancing our numerical capabilities for predicting VTOL aircraft noise in urban environments is essential. To achieve this goal, we have developed an integrated toolchain comprising three key components: Flight Mechanics, to accurately model aircraft behavior ; Noise Emission at the Source : to quantify the noise generated by the drones and finally Urban Environment Noise Propagation using the open-source tool NoiseModelling. This comprehensive toolchain enables the creation of detailed noise maps for specific drone scenario definitions. This paper presents an application of our toolchain in a parcel delivery scenario, featuring DJI Matrice 600 drones operating over a 11 km² sector of Madrid within a day period, incorporating five distribution centers with varying hourly capacities. The results include a range of informative noise indicators, taking into account noise level, number of flyovers and background noise levels.Pour intégrer efficacement les drones dans les infrastructures urbaines densément peuplées, il est crucial d'évaluer leur impact sur la qualité de vie de la population et d'atténuer tout effet néfaste. Étant donné que la pollution sonore engendrée par les survols de drones constitue une préoccupation majeure, améliorer nos capacités numériques pour prédire le bruit des aéronefs VTOL dans les environnements urbains est essentiel.Pour atteindre cet objectif, nous avons développé une chaîne d'outils intégrée composée de trois principaux éléments : la Mécanique de Vol , pour modéliser avec précision le comportement des aéronefs ; l'Émission de Bruit à la Source , pour quantifier le bruit généré par les drones ; et la Propagation du Bruit en Environnement Urbain en utilisant l'outil open-source NoiseModelling.Cette chaîne d'outils complète permet la création de cartes de bruit détaillées pour des définitions spécifiques de scénarios de drones.Ce document présente une application de notre chaîne d'outils sur un scénario de livraison de colis, basé sur une flotte de drones DJI Matrice 600 opérant au-dessus d'un secteur de 11 km² de Madrid sur une période journalière, avec cinq centres de distribution ayant des capacités horaires variées. Les résultats incluent une gamme d'indicateurs de bruit informatifs, prenant en compte le niveau de bruit, le nombre de survols et les niveaux de bruit de fond
One-dimensional flame subject to periodic and sinusoidal motion : frequency domain analysis and flame-motion contribution to combustion instability
No full textInternational audienceCombustion instabilities are often an outcome of the interaction between fluctuations in the flame-induced heat release rate (HRR) and acoustic modes of the combustor. Thus, they are a direct consequence of the flame unsteady dynamics, which itself features multiple contributions. The present study is focused on one of them, namely that of the flame motion. Two distinct spatial distributions of the HRR subject to a periodic and sinusoidal motion (slower than the speed of sound) are analyzed in terms of its normalized motion amplitude. For these two distributions, a frequency domain analysis is conducted and the presence of peaks at the motion frequency, together with higher harmonics, are put into evidence. Thus, it is established that, even in (i) a simplified one-dimensional situation and (ii) with a slow periodic and sinusoidal motion featuring moderate amplitudes, flame motions can drive an energy transfer from the fundamental frequency to upper harmonics. This serves as a basis for the development of a simplified model, which is found able to retrieve the corresponding response in terms of its fundamental and harmonic frequencies. Flame-flow couplings are subsequently analyzed on the basis of stability criteria based on the Rayleigh index, the Chu index and a nonlinear index. This leads to the identification of a threshold value of the normalized motion amplitude with the flame motion contribution acting either as a source term below this value or as a damping term once it is exceeded
Stratégies d'adaptation de maillage pour des simulations CFD sur des ensembles de conditions de fonctionnement
No full textInternational audienceIn computational fluid dynamics, evaluating accurately quantities of interest (global or local) requires capturing complex local phenomena and interactions, such as shocks and flow separations, while controlling the global error. The latter depends highly on the discretization of the computational domain, hence the mesh. In general, the location of the flow structures within the domain is sensitive to boundary and flow conditions. Proposing an a priori mesh with a discretization effort that concentrates on the demanding parts of the domain is thus usually impossible. Adaptive Mesh Refinement (AMR, [1,2,3,4]) is a method developed to iteratively adjust the local mesh resolution to the computed flow structures and construct meshes that achieve a prescribed accuracy for limited discretization and computational cost.This work concerns the problem of mesh adaptation when the operating conditions are variable and follow a prescribed continuous distribution. For instance, variability of the flow conditions appears in uncertainty quantification, operating domain analysis, and robust optimization. These analyses typically require many simulations for different conditions, making the cost-accuracy trade-off even more crucial for these problems. Several mesh adaption methods have been proposed for variable conditions ([5,6,7,8]), but they typically focus primarily on error control without simultaneously optimizing for cost.In this context, we propose two original methodologies. The first one, called Mean Mesh adaptation (MMA, [9,10]), builds a unique adapted mesh to minimize the average error over the continuous operating conditions for a given discretization effort. A key ingredient of MMA is using a small sample set of conditions to estimate the local average error at each iteration of the AMR process. The second method, Error-based Mesh Selection (EMS), tackles the optimal element selection within a library of adapted meshes to achieve the smallest possible error for any given flow conditions. The library consists of meshes independently adapted for different conditions in an offline stage, for cost efficiency, the selection uses a priori error estimations requiring no additional simulation.We used analytical and full CFD supersonic simulations [11,12] to analyze the proposed methods. We show that MMA is robust and accurately approximates the optimal mesh minimizing the average error for a limited construction cost (see figures 1 and 2). Similarly, EMS provides a robust approximation of the optimal selection with limited cost overheads (see figure 3). The EMS method is suitable to be extended for progressive library enrichment and a-posteriori correction of the error estimates
Hybridation optimisation-apprentissage pour la planification d'observations par un satellite
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Context-Adaptive GNSS/INS Estimation Strategies Based on Prior Statistical Multipath Knowledge
No full textInternational audienceModern mobile applications demand accurate and ubiquitous positioning, requiring approaches that explicitly account for environmental context. A major challenge in Global Navigation Satellite System (GNSS) positioning is multipath interference, which remains difficult to characterize and correct. This issue is particularly pronounced in low-cost GNSS receivers limited to pseudorange observables, which are highly susceptible to multipath errors. In this work, we present a novel statistical multipath model based on GNSS data collected in and around Toulouse, France, across four distinct environmental contexts: urban canyons, open sky, tree-covered areas, and general urban settings. These statistical models were derived using high-precision reference receivers. Leveraging this model, we propose a context-aware adaptation of standard approaches in GNSS positioning such as weighted least squares and extended Kalman filter estimators. Additionally, our method integrates tightly coupled Inertial Navigation System (INS) data and Doppler shift measurements, while employing robust outlier rejection techniques. We validate our approach using a second independent dataset collected in Carcassonne, France, demonstrating its effectiveness in improving positioning accuracy. Finally, we discuss potential extensions towards further context-adaptive GNSS estimators, aiming to enhance real-world applicability in diverse environments. Index Terms—Environmental Context, Adaptive Estimation, Multipath Mode
A generic framework to derive systems of conservation laws with source terms and its application to heat conduction in fluid flows: an alternative to the method of moments in kinetic theory of gases?
No full textInternational audienceA generic framework to derive systems of conservation laws through the Stationary Action Principle is proposed. The equations are expressed in Eulerian coordinates while the variation of the action assumes an underlying Lagrangian description thus avoiding the need for any Lin constraint. The resulting models admit a supplementary conservation equation for the evolution of the Hamiltonian. We then use the newly developed framework to derive a hyperbolic model that includes heat conduction in the compressible fluid dynamics equations through the introduction of a new variable called the thermal impulse. The resulting model has already been obtained previously through the Stationary Action Principle but its derivation relied on several non-standard assumptions. Our new framework allows not only to lift these assumptions, but also to recover them as a consequence of the Stationary Action Principle. Finally, a comparison with a model including heat conduction derived through the kinetic theory of gases is conducted
Dimensionnement des Qualités de Vol pour des véhicules aériens basé sur des polytopes de moment de contrôle
No full textInternational audienceThe study of Handling Qualities (HQ) constitutes an integral part of the air vehicle design process, ensuring safety and flyability. Nevertheless, traditional HQ sizing methods derived for conventional aircraft configurations provide decreasing insight on modern, unconventional, flight-control-augmented vehicles, mainly due to the lack of related operational experience. In this article, a new HQ sizing methodology is proposed aiming at a more vehicle-agnostic approach than existent techniques. Based on the concept of state-space polytopes, the method provides a means for visualizing the HQ requirements and comparing them to the vehicle's control authority. The polytopic representation serves to compact the dynamic HQ requirements down to a limited number of quasi-equilibrium calculations and allows for the analytic derivation of “HQ gradients” with respect to the vehicle's design features; simultaneously, non-linear control saturation aspects are accounted for. Test cases on two vehicles with complex, yet very different HQ characteristics - a Blended-Wing-Body (BWB) aircraft and an electric Vertical Take Off and Landing (eVTOL) vehicle - are selected to demonstrate the technique's effectiveness and potential application domain.L'étude des Qualités de Vol (QdV) constitue une partie intégrante du processus de conception des véhicules aériens, garantissant la sécurité et la praticabilité. Néanmoins, les méthodes traditionnelles de dimensionnement des QdV dérivées pour les configurations d'aéronefs conventionnels fournissent des informations de plus en plus limitées sur les véhicules modernes et non conventionnels, augmentés par des systèmes de commande de vol, principalement en raison du manque d'expérience opérationnelle liée. Dans cet article, une nouvelle méthodologie de dimensionnement des QdV est proposée, visant une approche plus agnostique vis-à-vis du véhicule que les techniques existantes. Basée sur le concept de polytopes dans l'espace des états, la méthode offre un moyen de visualiser les exigences en matière de QdV et de les comparer à l'autorité de contrôle du véhicule. La représentation polytopique permet de condenser les exigences dynamiques en matière de QdV en un nombre limité de calculs de quasi-équilibre et permet la dérivation analytique des "gradients de QdV" par rapport aux caractéristiques de conception du véhicule ; simultanément, les aspects de saturation de contrôle non linéaire sont pris en compte. Des cas de test sur deux véhicules présentant des caractéristiques de QdV complexes, mais très différentes - un avion à corps portant intégré (BWB) et un véhicule électrique à décollage et atterrissage verticaux (eVTOL) - sont sélectionnés pour démontrer l'efficacité de la technique et son domaine d'application potentiel
Online and in situ investigation of electron irradiation induced optical absorption in ZnGeP2 single crystals
No full textInternational audienceIn the present study, the absorbance induced in Zinc germanium diphosphide, ZnGeP 2 (ZGP) crystals and new Sn-doped ZGP crystals has been investigated under irradiation with high energy electrons. Online and in situ experiments were performed in the range 720-1100 nm. The spectra of the induced absorbance are constituted by a "tail" and the maximum appears to be located at wavelengths lower than those of the investigated spectral range. A fraction of the induced absorbance disappears within one minute after the electron beam is switched off, revealing the presence of metastable effects. A low and a high fluence contribution to the induced absorbance have been observed at 800 nm. The first reaches a limit value and seems to be affected by the Sn doping or by the absence of post-growth annealing, while the high fluence contribution does not feature a saturation in the investigated range and does not depend on the sample type
Towards a validated core memory model through (MP)SoC events
No full textInternational audienceThe certification of safety-critical systems requires amongst other things understanding the underlying hardware platform, and its use in the context of the system. At the processor level, it means that the designer must understand in detail the behaviour of a core executing a program. Many approaches rely on capturing such knowledge in an abstract model of the core. A crucial question is then does the model correctly represent the processor? and how can the designer prove such correctness? In this paper, we propose a methodology to build a core model, taking solely into account the memory accesses, and to validate the resulting model with associated stressing benchmarks
In-situ monitoring of the vacuum-bag-only consolidation process of CF/LM-PAEK composites with an embedded Fibre Bragg Grating sensor
No full textInternational audienceWe present a novel method for in-situ monitoring of the vacuum-bag-only (VBO) consolidation process of CF/LM-PAEK thermoplastic composites using an embedded Fibre Bragg Grating (FBG) sensor. An FBG sensor is first employed to monitor transverse strain in the plane during composite manufacturing. The data obtained from the embedded sensor demonstrate its sensitivity to thermal transitions of the thermoplastic matrix, including glass transition, crystallisation and melting. The coefficient of thermal expansion (CTE) of the composite material is also estimated using the FBG, with results validated by dilatometric measurements. Second, the sensitivity of the embedded FBG to consolidation phenomena, particularly the establishment of intimate contact between adjacent layers is also investigated. FBG-based monitoring of two different laminate configurations, one with raw prepreg plies and the other with pre-crystallised prepreg plies, confirms the sensor’s effectiveness in detecting the onset of intimate contact at the glass transition temperature. These findings highlight the potential of FBG-based monitoring for optimising composites manufacturing and improving quality control of high-performance thermoplastic composites