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Direct Software Coupling for Aeroplane Sizing and Integrated Aeroplane-Engine Mission Performance Simulations
Full text linkIn the context of increasing need for step change in civil aeroplane energy efficiency, many
innovative concepts are based on the idea of increasing integration of the traditionally segregated
subsystems, the most prominent ones particularly relying on synergies between the propulsive
system and the airframe. This paper presents a first step in building a multi-disciplinary
platform for directly coupled airframe-engine (propulsive system) mission preliminary sizing
and off-design performance estimation, constructed around commercial software Pacelab
APDTM and PROOSISTM. The developed framework enables the user to mission-size an
airframe (Pacelab APD) by directly querying a pre-sized engine model (PROOSIS). The
infrastructure that enables direct communication between the two programs is based on open
source methods, and is enabled by UDP sockets. Operational verification of the developed
framework is performed on a short-medium range case study - Airbus A320-200 aeroplane
and CFM56 engine cycle models. Several mission design loops and off-design simulations
were carried out in order to assess the flexibility and robustness of the coupled environment.
The preliminary results are coherent with respect to experience and theoretical expectations:
for fixed aerodynamic and weight characteristics, at constant maximum takeoff weight the
aeroplane range increases with increased engine bypass ratio and overall pressure ratio; the
range is reduced with increasing engine non-propulsive offtakes in off-design operation. In
turn, opposite tendencies were captured for the aeroplane maximum takeoff weight for a fixed
objective range. The coupled operation for the studied test cases behaves robustly as long
as the engine model is pre-sized and initialised carefully to match the aeroplane operating
envelope. The average calculation time of a complete coupled mission sizing is of order of one
minute. The presented work is a first step in a long-term effort to create a framework for
multi-disciplinary sizing and performance simulations of innovative aeroplane concepts, with
full system transparency available to the designer
Linear Fractional Transformation Modeling of Multibody Dynamics Around Parameter-Dependent Equilibrium
Full text linkThis brief proposes a new linear fractional transformation (LFT) modeling approach for uncertain linear parameter-varying (LPV) multibody systems with parameter-dependent equilibrium. Traditional multibody approaches, which consist of building the nonlinear model of the whole structure and linearizing it around equilibrium after a numerical trimming, do not allow to isolate parametric variations with the LFT form. Although additional techniques, such as polynomial fitting or symbolic linearization, can provide an LFT model, they may be time-consuming or miss worst case configurations. The proposed approach relies on the trimming and linearization of the equations at the substructure level, before assembly of the multibody structure, which allows to only perform operations that preserve the LFT form throughout the linearization process. Since the physical origin of the parameters is retained, the linearized LFT-LPV model of the structure exactly covers all the plants, in a single parametric model, without introducing conservatism or fitting errors. An application to the LFT-LPV modeling of a robotic arm is proposed; in its nominal configuration, the model obtained with the proposed approach matches the model provided by the software Simscape Multibody, but it is enhanced with parametric variations with the LFT form; a robust LPV synthesis is performed using MATLAB robust control toolbox to illustrate the capacity of the proposed approach for control design
Fast Nonlinear Static Aeroelasticity Method for High-Aspect-Ratio Wings at Different Mach Regimes
Full text linkA low-computational-cost method is proposed in this paper to predict steady-state nonlinear aeroelastic response for high-aspect-ratio wings. This fast nonlinear static aeroelasticity method relies on a simple but robust mathematical approach. The work presented in this paper evaluates the accuracy of a nonlinear aerodynamic method on a large range of Mach numbers for a geometry representative of a typical industrial high-aspect-ratio-wing aircraft. The robustness of the method relies on the accurate estimation of the local pressure field based on an aerodynamic database using a local incidence estimated with a vortex lattice method. The database can be filled with flight test, wind tunnel test, or high-fidelity numerical simulation. The structural deformation is provided by a coupled aeroelastic high-fidelity numerical simulation, and so this paper focuses mainly on the development and validation of the aerodynamic model. Then, the flexible coefficients of the wing are compared to the high-fidelity aeroelastic numerical simulations for a set of Mach numbers ranging from subsonic to transonic conditions. The results presented in this paper show that the present method is very accurate for low-Mach-number regimes (error is lower than 1% on lift), and it is also adapted to transonic flow regimes because the error on lift is lower than 5%. For high Mach numbers, the current solution commits larger errors on drag and pitching moment coefficients
Chapter 14: "Applicative GNC cases and examples"
No full textModern Spacecraft Guidance, Navigation, and Control: From System Modeling to AI and Innovative Applications provides a comprehensive foundation of theory and applications of spacecraft GNC, from fundamentals to advanced concepts, including modern AI-based architectures with focus on hardware and software practical applications. Divided into four parts, this book begins with an introduction to spacecraft GNC, before discussing the basic tools for GNC applications. These include an overview of the main reference systems and planetary models, a description of the space environment, an introduction to orbital and attitude dynamics, and a survey on spacecraft sensors and actuators, with details of their modeling principles. Part 2 covers guidance, navigation, and control, including both on-board and ground-based methods. It also discusses classical and novel control techniques, failure detection isolation and recovery (FDIR) methodologies, GNC verification, validation, and on-board implementation. The final part 3 discusses AI and modern applications featuring different applicative scenarios, with particular attention on artificial intelligence and the possible benefits when applied to spacecraft GNC. In this part, GNC for small satellites and CubeSats is also discussed. Modern Spacecraft Guidance, Navigation, and Control: From System Modeling to AI and Innovative Applications is a valuable resource for aerospace engineers, GNC/AOCS engineers, avionic developers, and AIV/AIT technicians
Étude à fine échelle de l'îlot de chaleur urbain par modélisation bayésienne à partir de données opportunes
Full text linkL’îlot de chaleur urbain (ICU), qui caractérise le différentiel de température entre un environnement urbain et le milieu rural environnant, est un phénomène météorologique à fort enjeu. Plus de la moitié de la population mondiale vit en ville où elle cohabite avec une biodiversité particulièrement vulnérable. En contexte de changement climatique, les vagues de chaleur deviennent plus fréquentes, leur durée et leur intensité augmentent. La hausse des températures due au milieu urbain s’ajoute à l’élévation de la température globale et accroît la vulnérabilité des citadins au stress thermique. L’observation de la température de l’air est essentielle pour faire avancer la recherche sur l’ICU, améliorer les prévisions numériques du temps en milieu urbain et éclairer les acteurs de l’aménagement qui souhaitent déployer des dispositifs d’atténuation. Or l’installation de réseaux de mesure urbains denses est coûteuse et la plupart des villes n’ont pas accès à l’observation fine échelle sur leur territoire. L’objectif de cette thèse est de montrer l’apport de données opportunes issues de stations météorologiques amateurs et de véhicules connectés, omniprésents en ville. Une méthodologie statistique qui fusionne ces mesures opportunes permet de produire une analyse fine échelle de l’ICU. En s’appuyant sur les réseaux professionnels des villes laboratoires de Dijon et Rennes, nous avons analysé chacune des deux sources de données pour mieux comprendre les causes des erreurs de mesure. Même si les observations opportunes sont particulièrement sujettes aux erreurs, des traitements proposés dans cette thèse permettent de les nettoyer efficacement afin d’en tirer un signal de qualité. Un modèle bayésien hiérarchique inféré avec l’approche INLA-SPDE est ensuite développé pour spatialiser les mesures opportunes et ainsi obtenir des cartes de l’ICU à pas de temps horaire et résolution hectométrique. Les cartographies obtenues sur Dijon sont cohérentes avec le réseau de référence et la racine de l’erreur quadratique moyenne est inférieure à 1°C. Ces résultats ouvrent la voie à de nouvelles perspectives en terme de recherche, par exemple pour l’évaluation de simulations des modèles de ville, mais aussi pour la constitution d’observations spatialisées utilisables en post-traitement des sorties de la prévision numérique du temps. Les cartographies permettront aussi d’éclairer les acteurs de l’aménagement urbain au regard de la problématique de l’ICU
Liens entre le parasite d'amphibiens Batrachochytrium dendrobatidis et les biofilms benthiques de lacs de montagne pyrénéens
Full text linkMountain freshwater ecosystems provide essential services to humanity, such as the provision of clean water, but are strongly affected by anthropogenic global change despite their apparent isolation. Benthic biofilms, communities of organisms living in a matrix adhering to submerged surfaces, have critical functions in mountain lakes: among others, they detoxify water and form the basis of food webs. However, their composition and biodiversity are still poorly understood. Also, in the Pyrenees, some amphibian populations are threatened by chytridiomycosis, an infectious disease caused by the zoosporic fungus Batrachochytrium dendrobatidis (Bd). Its epidemiology is not fully understood but may depend on biofilms, which are abundant in mountain lakes and form the food of tadpoles.
Here, I had two main objectives: first, to study the spatio-temporal variations of biofilm microbial biodiversity; second, to investigate the potential role(s) of biofilms in the epidemiology of Bd infections. To do this, I performed a metataxonomic analysis of the prokaryotic and microeukaryotic assemblages of 230 biofilm samples collected from 2016 to 2020 in 26 Pyrenean mountain lakes. Combining this with Bd infection data from tadpoles sampled in the same lakes, I explored the links between the microbial composition of biofilms and the distribution, frequency and population impacts of Bd infections. In the laboratory, I also tested whether a biofilm could affect the free-living, infectious stage of Bd, the zoospore. My hypotheses were that the biodiversity of biofilms would decrease and their assemblages would change over the course of the study, that biofilms from lakes with less infected/impacted amphibian populations would contain more Bd antagonists than biofilms from other lakes, and that biofilms produced in the laboratory would not affect the number of zoospores unless they contained Bd consumers.
The diversity in both prokaryotic and micro-eukaryotic biofilm assemblages decreased over the study period. Their compositions also changed over the five years, with an increase in cyanobacteria (possibly toxigenic organisms) in prokaryotes and a decrease in diatoms (indicator organisms) in micro-eukaryotes. Taken together, these results show that benthic biofilm communities are degrading with potentially negative implications for the entire aquatic ecosystem and water quality. In addition, I found that biofilms in lakes where amphibians are less infected and less impacted by Bd had a higher abundance of Bd-inhibiting or Bd-consuming organisms. Finally, I showed that biofilms, even when they do not contain Bd consumers but only a phototrophic alga, can affect Bd zoospores by inactivating them or forcing them to immobilise.
My transdisciplinary research illustrates the interactions between environmental health and animal and public health. Contemporary environmental changes are deteriorating biofilms, the very basis of food webs in mountain lakes. This is likely to have profound cascading effects on mountain socio-ecosystems as a whole, such as a potential increase in the risk of Bd infection and chytridiomycosis for amphibians, and cyanotoxicosis for all vertebrates that frequent mountain lakes, including humans and livestock. If mountain freshwater ecosystems are to continue to provide services rather than disservices, the factors contributing to biofilm change will need to be rapidly identified and mitigated
Modeling and Design Optimization of an Electric Environmental Control System for Commercial Passenger Aircraft
Full text linkThe aircraft environmental control system (ECS) is the second-highest fuel consumer system, behind the propulsion system. To reduce fuel consumption, one research direction intends to replace conventional aircraft with more electric aircraft. Thus, new electric architectures have to be designed for each system, such as for the ECS. In this paper, an electric ECS is modeled and then sized and optimized for different sizing scenarios with the aim of minimizing fuel consumption at the aircraft level. For the system and for each component, such as air inlets and heat exchangers, parametric models are developed to allow the prediction of relevant characteristics. These models, developed in order to be adapted to aircraft design issues, are of different types, such as scaling laws and surrogate models. They are then assembled to build a preliminary sizing procedure for the ECS by using a multidisciplinary design analysis and optimization (MDAO) formulation. Results show that the ECS design is highly dependent on the sizing scenario considered. An approach to size the ECS globally with respect to all the sizing scenarios leads to an ECS that accounts for around 200 N of drag, 190 kW of electric power, and 1500 kg of mass for the CeRAS aircraft
Diffusive series representation for the Crandall model of acoustic impedance
Full text linkPorous media used in soundproofing
systems can be modeled as a set of cylindrical per-
forations. Starting from the classical expression of
the acoustic impedance of cylindrical tubes which
is proportional to a ratio of Bessel functions, this
paper briefly presents the derivation of an equivalent
expression depending only on the positive zeros of J 2 ,
the Bessel function of the first kind of order 2. In the
frequency domain, such a derivation is of great prac-
tical interest because it replaces the costly evaluation
of transcendental functions by that of rational ones. In
the time domain, the impulse response of the cylin-
drical tube reduces to a Prony series of which only
10 terms prove sufficient to reliably describe it, for
any values of physical parameters within the acous-
tic model assumptions. The method applied in this
use case from acoustics was primarily employed by
Giusti and Mainardi (Meccanica 51(10): 2321–2330,
2016) in their study of pulse propagation within
blood vessels and by Colombaro et al. (Meccanica 52(4–5):825–832, 2017) in their work on the Bessel
models of linear viscoelasticity
On the Equivalence between Kalman Filter at Steady State and DPLL
Full text linkFundamental results in the literature previously showed that a class of Kalman filter converges to a digital phase lock loop (DPLL) structure at the second and third order. We generalize these results at any order and give the closed-form linear relation, and its inverse, between the steady-state Kalman gains and the loop filter constants. Both relations are simple and only involve Stirling numbers of the first and second kind. This new result may help in a deeper understanding of the equivalence between Kalman filter and DPLL and be of practical interest in high dynamic scenarios
LES of the T106 low-pressure turbine: spectral proper orthogonal decomposition of the flow based on a fluctuating energy norm
Full text linkThis paper investigates the use of the spectral proper orthogonal decomposition (SPOD) on the flow around the T106 low-pressure turbine cascade. The chosen metric of the SPOD is based on the hydrodynamic flow disturbances for compressible flows and is used to characterize the flow structures holding large energy disturbances and synchronization processes with incoming wakes when considered. The input data for the SPOD is provided by large-eddy simulations of the T106 cascade. The Reynolds number and free-stream turbulence effects on the flow structures are studied using four operating points investigated in previous experiments and numerical simulations: Reynolds numbers of \RE~=~\num{5.18e4} and \RE~=~\num{1.48e5} without and with upstream wakes. The analysis of the SPOD indicates that the upstream wakes can amplify some modes of the suction side boundary layer (apparently a receptivity mechanism) and intensify the developing blade wake turbulent structures downstream of the trailing edge. This amplification happens over a reduced frequency bandwidth between Strouhal numbers equal to 7-10 for the low Reynolds number case and 20-24 for the high Reynolds number case