Search

Patient safety is an activity to mitigate preventable patient harm that may occur during the delivery of medical care. The European Board of Anaesthesiology (EBA)/European Union of Medical Specialists had previously published safety recommendations on minimal monitoring and postanaesthesia care, but with the growing public and professional interest it was decided to produce a much more encompassing document. The EBA and the European Society of Anaesthesiology (ESA) published a consensus on what needs to be done/achieved for improvement of peri-operative patient safety. During the Euroanaesthesia meeting in Helsinki/Finland in 2010, this vision was presented to anaesthesiologists, patients, industry and others involved in health care as the ‘Helsinki Declaration on Patient Safety in Anaesthesiology'. In May/June 2020, ESA and EBA are celebrating the 10th anniversary of the Helsinki Declaration on Patient Safety in Anaesthesiology; a good opportunity to look back and forward evaluating what was achieved in the recent 10 years, and what needs to be done in the upcoming years. The Patient Safety and Quality Committee (PSQC) of ESA invited experts in their fields to contribute, and these experts addressed their topic in different ways; there are classical, narrative reviews, more systematic reviews, political statements, personal opinions and also original data presentation. With this publication we hope to further stimulate implementation of the Helsinki Declaration on Patient Safety in Anaesthesiology, as well as initiating relevant research in the future.

Stability analysis on a supersonic natural laminar flow (NLF) wing designed by JAXA was performed at both flight and wind tunnel test conditions as a joint research program between ONERA and JAXA. Both parties validated the NLF wing effect by confirming suppression of crossflow instability at design point, using an e(N) method with fixed β strategy proposed by ONERA. Although JAXA’s flight test vehicle and wind tunnel test model had almost same averaged roughness height of about 1micrometer, it was shown that surface roughness had little influence on measured transition location at both flight and wind tunnel test conditions. Furthermore, JAXA found that the pressure distribution measured in flight test did not completely coincide to the target pressure distribution (Cp (Target)) for the NLF wing design. It revealed that measured transition location at outer wing region was not delayed in flight test, compared with the transition location predicted with the Cp (Target) which had large gain to delay the transition. Influence of Reynolds number on transition location was also studied for the target pressure distribution Cp (Target). Consequently, chordwise transition location, (x/c)Tr., rapidly moves from mid-chord location to forward location (near leading edge) for increasing Reynolds numbers, according to the change of instability of boundary layer from Tollmien-Schlichting instability to crossflow instability., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA0062081000, レポート番号: JAXA-RR-12-009E

International audience; This paper presents some developments performed to achieve an accurate and efficient prediction tool for laminar/turbulent transition. These developments involve industrial codes used at Dassault Aviation for the aerodynamics design of military aircraft and business jets. The process is based on a flexible sequence of simulation tools. The issues concerning influence of the numerical solvers, transition onset criteria and the coupling process are described. The influence of intermittency function is also discussed. Results demonstrate the accuracy of the method with emphasis on transition induced by crossflow instabilities.

The transition from a laminar to a turbulent flow strongly modifies the boundary layer properties. Understanding the mechanisms leading to transition is crucial to reliably predict aerodynamic performances. For boundary layers subjected to high levels of external disturbances, the natural transition due to the amplification of the least stable mode is replaced by an early transition, called Bypass transition. This is the result of non-normal mode interactions that lead to a phenomenon of transient growth of disturbances. These disturbances are known as Klebanoff modes and take the form of streamwise velocity streaks. This thesis aims at understanding this linear mechanism of transient growth and quantifying its influence on the classical modal amplification of disturbances. This is done by computing the so-called optimal perturbations, i.e. the initial disturbances that undergo maximum amplification in the boundary layer. These optimal perturbations are first determined for two-dimensional compressible boundary layers developing over curved surfaces. In particular, we show that Klebanoff modes naturally evolve towards Görtler vortices that occur over concave walls. Three-dimensional boundary layers are then considered. In such configurations, transient growth provides an initial amplitude to crossflow vortices. Finally, applying the tools developed in this thesis to new flow cases such as swept wings provides further understanding of the phenomenon of transient growth for realistic geometries. Le passage du régime laminaire au régime turbulent s’accompagne d’importantes modifications des propriétés physiques de la couche limite. La détermination précise de la transition est donc cruciale dans de nombreux cas pratiques. Lorsque la couche limite se développe dans un environnement extérieur faiblement perturbé, la transition est gouvernée par l’amplification du mode propre le moins stable. Lorsque l’intensité des perturbations extérieures augmente, des interactions multimodales entraînent une amplification transitoire des perturbations. Ce phénomène peut conduire à une transition prématurée, appelée transition Bypass. Les perturbations prennent alors la forme de stries longitudinales de vitesse appelées modes de Klebanoff. L’objectif de cette thèse est d’étudier ce mécanisme linéaire de croissance transitoire et son influence sur l’amplification modale classique des perturbations. Cela passe par la détermination des perturbations les plus amplifiées au sein de la couche limite, appelées perturbations optimales. Ces perturbations optimales sont d’abord calculées pour des couches limites bidimensionnelles et compressibles se développant sur des surfaces courbes. En particulier, on montre que les modes de Klebanoff évoluent vers les tourbillons de Görtler qui se forment sur des parois concaves. Le cas plus général de couches limites tridimensionnelles est ensuite envisagé. Pour de telles configurations, la croissance transitoire fournit une amplitude initiale aux instabilités transversales. Enfin, l’application des outils développés dans cette thèse fournit de nouveaux résultats pour des cas d’écoulements autour de géométries réalistes comme une aile en flèche.

La détermination de la position de la transition laminaire/turbulent est un enjeu majeur de l'aérodynamique moderne. De nombreuses expériences ont montré qu'au sein de couches limites soumises à de fortes perturbations extérieures, le scénario classique de transition par ondes de Tollmien-Schlichting n'est plus valide. Dans de telles conditions, les perturbations prennent la forme de modes de Klebanoff plus communément appelés stries. Ces stries peuvent être amplifiées de façon transitoire et déclencher une transition prématurée, dite Bypass, signifiant que la transition naturelle a été court-circuitée. Le problème est qu'à l'heure actuelle, il n'existe pas de modèle permettant de prévoir cette transition Bypass. L'objectif de cette thèse est de proposer un critère de transition lorsque l'étude du mode de Tollmien-Schlichting ne fournit plus de renseignements pertinents. La première étape a consisté à déterminer les caractéristiques des stries les plus amplifiées dans une couche limite bidimensionnelle compressible ; bien que cette approche fournisse des résultats cruciaux, les stries ainsi calculées correspondent à un état optimum qui peut se révéler très éloigné de l'état physique obtenu expérimentalement. L'étape suivante a donc consisté à mettre en place un modèle, s'appuyant sur la théorie des perturbations optimales, permettant de prévoir la transition Bypass au sein de couches limites soumises à un environnement extérieur fortement perturbé. L'application du modèle à des couches limites soumises à une forte turbulence extérieure ou se développant sur des parois rugueuses a fournit des résultats pertinents aux regards des valeurs expérimentales existantes. Determination of the laminar/turbulent transition location is a major task of numerical aerodynamic. Many experiments have demonstrated that inside boundary layers subjected to high external disturbances the classical transition scenario involving the Tollmien-Schlichting waves is no longer valid. In such circumstances, perturbations take the form Klebanoff modes commonly named streaks. These streaks can be amplified in a transient way and trigger an early Bypass transition, meaning that the natural one has been short-circuited. The problem is that up to now there is no model to predict Bypass transition. This thesis aims at developing a transition criterion when the TS wave theory stops being relevant. The first step has consisted in numerically determine the characteristics of the most amplified streaks for a two-dimensional compressible boundary layer. Nonetheless, even-though this approach provides decisive results, the computed streaks correspond to an optimum state with may be different from the physic state experimentally observed. The following step has thus consists in developing a model, based on optimal perturbation theory, able to predict the Bypass transition induced by high external disturbances. Model computations concerning boundary layers subjected to high free-stream turbulence or developing on walls characterised by surface defaults provide relevant results compared to existing experimental values.

Laminar turbulent transition is known for a long time as a critical phenomenon influencing the thermal load encountered by hypersonic vehicle during their planetary re-entry trajectory. Despite the efforts made by several research laboratories all over the world, the prediction of transition remains inaccurate, leading to oversized thermal protection system and dramatic limitations of hypersonic vehicles performances. One of the reasons explaining the difficulties encountered in predicting transition is the wide variety of parameters playing a role in the phenomenon. Among these parameters, surface roughness is known to play a major role and has been investigated in the present thesis.A wide bibliographic review describing the main parameters affecting transition and their coupling is proposed. The most popular roughness-induced transition predictions correlations are presented, insisting on the lack of physics included in these methods and the difficulties encountered in performing ground hypersonic transition experiments representative of real flight characteristics. This bibliographic review shows the importance of a better understanding of the physical phenomenon and of a wider experimental database, including real flight data, for the development of accurate prediction methods.Based on the above conclusions, a hypersonic experimental test campaign is realized for the characterization of the flow field structure in the vicinity and in the wake of 3D roughness elements. This fundamental flat plate study is associated with numerical simulations for supporting the interpretation of experimental results and thus a better understanding of transition physics. Finally, a model is proposed in agreement with the wind tunnel observations and the bibliographic survey.The second principal axis of the present study is the development of a hypersonic in-flight roughness-induced transition experiment in the frame of the European EXPERT program. These flight data, together with various wind tunnel measurements are very important for the development of a wide experimental database supporting the elaboration of future transition prediction methods., Doctorat en Sciences de l'ingénieur, info:eu-repo/semantics/nonPublished

Laminar turbulent transition is known for a long time as a critical phenomenon influencing the thermal load encountered by hypersonic vehicle during their planetary re-entry trajectory. Despite the efforts made by several research laboratories all over the world, the prediction of transition remains inaccurate, leading to oversized thermal protection system and dramatic limitations of hypersonic vehicles performances. One of the reasons explaining the difficulties encountered in predicting transition is the wide variety of parameters playing a role in the phenomenon. Among these parameters, surface roughness is known to play a major role and has been investigated in the present thesis. A wide bibliographic review describing the main parameters affecting transition and their coupling is proposed. The most popular roughness-induced transition predictions correlations are presented, insisting on the lack of physics included in these methods and the difficulties encountered in performing ground hypersonic transition experiments representative of real flight characteristics. This bibliographic review shows the importance of a better understanding of the physical phenomenon and of a wider experimental database, including real flight data, for the development of accurate prediction methods. Based on the above conclusions, a hypersonic experimental test campaign is realized for the characterization of the flow field structure in the vicinity and in the wake of 3D roughness elements. This fundamental flat plate study is associated with numerical simulations for supporting the interpretation of experimental results and thus a better understanding of transition physics. Finally, a model is proposed in agreement with the wind tunnel observations and the bibliographic survey. The second principal axis of the present study is the development of a hypersonic in-flight roughness-induced transition experiment in the frame of the European EXPERT program. These flight data, together with various wind tunnel measurements are very important for the development of a wide experimental database supporting the elaboration of future transition prediction methods., Doctorat en Sciences de l'ingénieur, info:eu-repo/semantics/published

Réduire la traînée d'un avion permet de diminuer les coûts du transport aérien, enjeux des plus stratégiques. Dans ce but, le maintien d'une couche limite laminaire étendue permet une forte réduction de la traînée de frottement. Les progrès réguliers dans ce domaine ont débouché sur l'optimisation des profils d'aile, et sur la sensibilisation de la couche limite par aspiration au travers de parois poreuses. Ces techniques ont été testées en vol sur la voilure d'un Falcon 900, avec Dassault Aviation, faisant apparaître des écarts entre prévisions et mesures de transition. Ces écarts ont été attribués à des défauts de géométrie (ondulations) de la voilure, et ont motivé un important travail d'analyse. Il a été décidé de développer une nouvelle génération de critères de tolérance de forme, basés non plus sur des corrélations empiriques globales, mais sur les analyses de stabilité de la couche limite. La théorie de la stabilité permet, en effet, de caractériser la croissance des instabilités, la mesure de cette croissance se faisant au moyen du facteur N. Une modélisation du saut de facteur N en fonction des paramètres caractérisant la déformation géométrique permet de prévoir, à partir de l'étude de la géométrie de base, quels seront les effets sur la transition. La démarche employée consiste en une série d'études expérimentales et numériques, de complexité croissante, permettant d'affiner progressivement les lois de variations physiques et leur modélisation. L'ensemble de ces travaux a permis l'élaboration d'un critère tenant compte de l'ensemble des paramètres étudiés et permettant une bonne estimation de la position de transition pour les différentes configurations. Enfin des déformations tridimensionnelles ont été examinées ; cette étude à mis en évidence, pour certaines configurations, la prépondérance des effets tridimensionnels. Reducing plane drag is a key objective for decreasing air transportation costs and increasing competitiveness of aircraft manufacturers. A way to achieve this is to increase the laminar boundary layer extent over the wing. Progresses in this direction have been demonstrated thanks to wing profile optimization and wall suction, leading to a global reduction of the friction drag. Theses techniques were tested in flight on a Falcon 900 modified wing, with Dassault Aviation. Lack of agreement between experimental results and predictions were observed, that apparently was due to small wall imperfections of the wing glove. It was then decided to define new criterion for shape tolerances, based on stability analysis. Stability theory is today the reference tool for transition prediction, coupled with the eN method. Modelling the evolution of this N-factor as a function of growth and location of surface waviness can be used to predict the effect on transition. A series of experimental and numerical studies, of increasing complexity, was conducted so that key physical parameters were identified and modelled the final synthesis allows to elaborate a criterion taking into account every parameters considered, and giving the location of transition in presence of waviness. Finally 3D waviness were also rapidly evaluated.