Locating a weak change using diffuse waves (LOCADIFF) : theoretical approach and inversion procedure

We describe a time-resolved monitoring technique for heterogeneous media. Our approach is based on the spatial variations of the cross-coherence of coda waveforms acquired at fixed positions but at different dates. To locate and characterize a weak change that occurred between successive acquisitions, we use a maximum likelihood approach combined with a diffusive propagation model. We illustrate this technique, called LOCADIFF, with numerical simulations. In several illustrative examples, we show that the change can be located with a precision of a few wavelengths and its effective scattering cross-section can be retrieved. The precision of the method depending on the number of source receiver pairs, time window in the coda, and errors in the propagation model is investigated. Limits of applications of the technique to real-world experiments are discussed.Comment: 11 pages, 14 figures, 1 tabl

Simulation and evaluation of sustainable climate trajectories for aviation

In 2019, aviation was responsible for 2.6% of world CO2 emissions as well as additional climate impacts such as contrails. Like all industrial sectors, the aviation sector must implement measures to reduce its climate impact. This paper focuses on the simulation and evaluation of climate scenarios for air transport. For this purpose, a specific tool (CAST for “Climate and Aviation - Sustainable Trajectories”) has been developed at ISAE-SUPAERO. This tool follows a methodology for the assessment of climate impacts adapted to aviation. Firstly, models for the main levers of action, such as air traffic, aircraft energy consumption and energy decarbonization, are provided using trend projections from historical data or assumptions from the literature. Second, the evaluation of scenarios is based on aviation carbon budgets, which are also extended to non-CO2 effects using the concept of GWP*. Several scenario analyses are performed in this paper using CAST allowing different conclusions to be drawn. For instance, the modelling of the scenarios based on the more recent ATAG (Air Transport Action Group) commitments shows that aviation would consume 6.5% of the world carbon budget for +1.5 ◦C. Some illustrative scenarios are also proposed. By allocating 2.6% of the world carbon budget to aviation, it is shown that air transport is compatible with a +2 ◦C trajectory when the annual growth rate of air traffic varies between +1.8% and +2.9%, depending on the technological improvements considered. However, using the same methodology for a +1.5 ◦C trajectory shows that a drastic decrease in air traffic is necessary. Lastly, analyses including non- CO2 effects emphasize the importance of implementing specific strategies for mitigating contrails

Modeling and Design Optimization of an Electric Environmental Control System for Commercial Passenger Aircraft

The 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

Aircraft fleet models using a bottom-up approach for simulating aviation technological prospective scenarios

Modeling prospective scenarios for aviation in the context of climate issues is a scientific topic of major interest. For this purpose, the development of models to integrate technological improvements in these scenarios is necessary. This paper focuses on the use of a bottom-up approach to establish aircraft fleet models, in order to integrate them into CAST, an open-source tool for simulating and evaluating prospective scenarios for air transport. These models are based on logistic functions which allow representing the gradual replacement of current aircraft by future aircraft architectures obtained from overall aircraft design. The efficiency improvement of the aircraft fleet can then be assessed. To illustrate the use of the models, some case studies, considering for example turboprop and hydrogen aircraft, are performed for analyzing efficiency scenarios for air transport. Also, the effect of accelerated fleet renewal and earlier introduction of new aircraft architectures is studied

Sizing and optimization of a more electric aircraft integrating short-term incremental technologies

In order to reduce the environmental impact of aviation, one of the solutions is to develop more efficient aircraft. These gains can be achieved in different fields such as propulsion, aerodynamics or electrification of systems. This paper focuses on the sizing and optimization of BEITA, a short-medium range aircraft architecture available in the short term by 2025-2030. The aircraft is based on incremental technologies for propulsion, aerostructure and bleedless systems. Light-weight models are proposed for the different improvements, particularly for more electric systems. FAST-OAD, an open source framework for rapid overall aircraft design based on multidisciplinary design analysis and optimization, is used to size the new architecture and a specific life cycle assessment module is used to estimate the environmental impacts. BEITA allows a reduction in fuel consumption of 15% compared to the CeRAS reference aircraft. Optimizations of this architecture are achieved minimizing different cost functions. This study ends with a sizing on a shorter range based on specific payload-range diagrams

Aviation and climate: the state-of-the-art

As a human activity, the aviation sector is a contributor to climate change due the CO2 emissions and also non-CO2 effects which result from the interactions of the engine effluents with the atmosphere. The understanding and quantification of the impact of the aviation sector on climate is an intricate topic, whose evaluation largely depends on the scope considered. Furthermore, identifying the possible and efficient levers to mitigate such impact is of interest. This paper proposes a short review of the scientific literature regarding aviation and climate. Furthermore, it proposes an analysis of prospective decarbonisation scenarios for the sector in the context of the Paris Agreement. The results indicate that the ability of the aviation sector to reduce its CO2 emissions by 2050 thanks to technological levers (including progresses in aerodynamics and propulsion) alone depends on the objective for the limitation of temperature increase by 2100. For an objective of +1.5 °C, if air traffic grows at the rate predicted by the aviation industry, it will consume a larger share of the carbon budget than its current share of CO2 emissions. Also, the results are compelling in regard of the low-carbon energy availability for the aviation sector

Du dimensionnement de systèmes et d’architectures en conception avion à la simulation de scénarios prospectifs durables pour le transport aérien

Air transport is currently responsible for 2 to 3 % of world CO2 emissions, as well as additional climate and environmental impacts. There is therefore great interest in new aircraft concepts that can contribute to reducing the environmental impact of aviation. The objective of this thesis is to contribute to the development of a holistic approach, from the modeling and sizing of new aircraft architectures to the simulation of prospective sustainable scenarios for air transport. This approach allows linking the issues of aircraft design to those of the analysis of prospective scenarios for aviation. In a first part, estimation models for different aircraft systems are presented in the context of more electric aircraft. Various methods are applied, for instance based on the use of energy approaches or regression models. Environmental control systems and ice protection systems are studied, as well as systems induced by the aircraft electrification (generation and distribution of electrical power, thermal management).In a second part, a new aircraft architecture deployable in the short term is sized through an approach based on the use of the aircraft design platform FAST-OAD. This architecture integrates the systems described above, whose performance is evaluated individually beforehand using specific models, as well as propulsive and aero-structural improvements. The characteristics of the complete architecture are then analyzed, notably concerning its environmental impacts from a life cycle assessment module developed for FAST-OAD. In the last part, the CAST tool developed in this thesis is presented. It allows simulating and evaluating prospective scenarios for air transport. Models are detailed for the different levers of action to reduce the environmental impact of air transport. Particular attention is paid to the introduction of more efficient architectures in the fleet. To assess the sustainability of the scenarios, specific methodologies are proposed for climate and energy issues, by relying for instance on the concept of carbon budget. Several applications show the benefits of new technologies but also the need for a trade-off between the level of air traffic and the share of the world carbon budget allocated to the aviation sector.Le transport aérien est à ce jour responsable de 2 à 3 % des émissions mondiales de CO2, ainsi que d'autres impacts climatiques et environnementaux. Les nouveaux concepts d'architectures pouvant contribuer à la réduction de l’impact environnemental de l'aviation suscitent donc un grand intérêt. L’objectif de cette thèse est de contribuer au développement d’une approche holistique, allant de la modélisation et du dimensionnement de nouvelles architectures avion à la simulation de scénarios prospectifs durables pour le transport aérien. Cette approche permet ainsi de relier les enjeux de la conception avion à ceux de l’analyse de scénarios prospectifs pour l’aviation. Dans une première partie, des modèles d'estimation pour différents systèmes avion sont présentés dans le cadre d’un avion plus électrique. Des méthodes variées sont appliquées, par exemple basées sur l’utilisation de modèles énergétiques ou de modèles de régression. Les systèmes de conditionnement d’air et de protection contre le givre sont étudiés, tout comme les systèmes induits par l’électrification des avions (génération et distribution de puissance électrique, management thermique). Dans une deuxième partie, une architecture avion déployable à court terme est dimensionnée à travers une approche basée sur l’utilisation de la plateforme de conception avion FAST-OAD. Cette architecture intègre les systèmes décrits précédemment, dont les performances sont préalablement évaluées individuellement via des modèles spécifiques, ainsi que des améliorations propulsives et aéro-structurelles. Les caractéristiques de l'architecture complète sont alors analysées, notamment concernant ses impacts environnementaux à partir d'un module d'analyse de cycle de vie développé pour FAST-OAD.Dans une dernière partie, l'outil CAST développé dans cette thèse est présenté. Il permet de simuler et d'évaluer des scénarios prospectifs pour le transport aérien. Des modèles sont détaillés pour les différents leviers d’action permettant de réduire l'impact environnemental du transport aérien. Une attention particulière est portée sur l’introduction d’architectures plus efficaces dans la flotte. Pour évaluer la durabilité des scénarios, des méthodologies spécifiques sont proposées pour les enjeux climatiques et énergétiques, en s'appuyant par exemple sur la notion de budget carbone. Plusieurs applications montrent alors le bénéfice des nouvelles technologies mais aussi le besoin d’un arbitrage entre le niveau de trafic aérien et la part du budget carbone mondial allouée au secteur aérien

From the sizing of systems and architectures in aircraft design to the simulation of sustainable prospective scenarios for air transport

Le transport aérien est à ce jour responsable de 2 à 3 % des émissions mondiales de CO2, ainsi que d'autres impacts climatiques et environnementaux. Les nouveaux concepts d'architectures pouvant contribuer à la réduction de l’impact environnemental de l'aviation suscitent donc un grand intérêt. L’objectif de cette thèse est de contribuer au développement d’une approche holistique, allant de la modélisation et du dimensionnement de nouvelles architectures avion à la simulation de scénarios prospectifs durables pour le transport aérien. Cette approche permet ainsi de relier les enjeux de la conception avion à ceux de l’analyse de scénarios prospectifs pour l’aviation.Dans une première partie, des modèles d'estimation pour différents systèmes avion sont présentés dans le cadre d’un avion plus électrique. Des méthodes variées sont appliquées, par exemple basées sur l’utilisation de modèles énergétiques ou de modèles de régression. Les systèmes de conditionnement d’air et de protection contre le givre sont étudiés, tout comme les systèmes induits par l’électrification des avions (génération et distribution de puissance électrique, management thermique).Dans une deuxième partie, une architecture avion déployable à court terme est dimensionnée à travers une approche basée sur l’utilisation de la plateforme de conception avion FAST-OAD. Cette architecture intègre les systèmes décrits précédemment, dont les performances sont préalablement évaluées individuellement via des modèles spécifiques, ainsi que des améliorations propulsives et aéro-structurelles. Les caractéristiques de l'architecture complète sont alors analysées, notamment concernant ses impacts environnementaux à partir d'un module d'analyse de cycle de vie développé pour FAST-OAD.Dans une dernière partie, l'outil CAST développé dans cette thèse est présenté. Il permet de simuler et d'évaluer des scénarios prospectifs pour le transport aérien. Des modèles sont détaillés pour les différents leviers d’action permettant de réduire l'impact environnemental du transport aérien. Une attention particulière est portée sur l’introduction d’architectures plus efficaces dans la flotte. Pour évaluer la durabilité des scénarios, des méthodologies spécifiques sont proposées pour les enjeux climatiques et énergétiques, en s'appuyant par exemple sur la notion de budget carbone. Plusieurs applications montrent alors le bénéfice des nouvelles technologies mais aussi le besoin d’un arbitrage entre le niveau de trafic aérien et la part du budget carbone mondial allouée au secteur aérien.Air transport is currently responsible for 2 to 3 % of world CO2 emissions, as well as additional climate and environmental impacts. There is therefore great interest in new aircraft concepts that can contribute to reducing the environmental impact of aviation. The objective of this thesis is to contribute to the development of a holistic approach, from the modeling and sizing of new aircraft architectures to the simulation of prospective sustainable scenarios for air transport. This approach allows linking the issues of aircraft design to those of the analysis of prospective scenarios for aviation.In a first part, estimation models for different aircraft systems are presented in the context of more electric aircraft. Various methods are applied, for instance based on the use of energy approaches or regression models. Environmental control systems and ice protection systems are studied, as well as systems induced by the aircraft electrification (generation and distribution of electrical power, thermal management).In a second part, a new aircraft architecture deployable in the short term is sized through an approach based on the use of the aircraft design platform FAST-OAD. This architecture integrates the systems described above, whose performance is evaluated individually beforehand using specific models, as well as propulsive and aero-structural improvements. The characteristics of the complete architecture are then analyzed, notably concerning its environmental impacts from a life cycle assessment module developed for FAST-OAD.In the last part, the CAST tool developed in this thesis is presented. It allows simulating and evaluating prospective scenarios for air transport. Models are detailed for the different levers of action to reduce the environmental impact of air transport. Particular attention is paid to the introduction of more efficient architectures in the fleet. To assess the sustainability of the scenarios, specific methodologies are proposed for climate and energy issues, by relying for instance on the concept of carbon budget. Several applications show the benefits of new technologies but also the need for a trade-off between the level of air traffic and the share of the world carbon budget allocated to the aviation sector