Aerodynamic simulation strategies assessment for a Fenestron® in hover flight

The Fenestron® has a crucial anti-torque function and its sizing is a key point of the Helicopter design, especially regarding thrust and power predictions. This paper reports the investigations done on a full scale Dauphin Fenestron®. The objectives are first to evaluate the influence of some numerical parameters on the performance of the Fenestron®. Then the flow is analyzed for a high incidence pitche, for which the rotor blade can experience massive boundary layer separations. Simulations are carried out on a single blade passage model. Several parameters are benched, such as grid quality, numerical schemes and turbulence modeling. A comparison with test bench measurements is carried out to evaluate the capability of the numerical simulations to predict both global performance (thrust and power) and local flows (static pressure at the shroud and radial profiles inside the vein). The analysis demonstrates the capability of numerical simulations to accurately estimate the global performance of the Fenestron®, including at high pitch angles. However, some discrepancies remain on the local flow, especially in the vicinity of the rotor shroud. A more detailed analysis of the local flow is performed at a blade pitch angle of 35°, with a particular interest for the blade tip region

Lethal Nipah Virus Infection Induces Rapid Overexpression of CXCL10

Nipah virus (NiV) is a recently emerged zoonotic Paramyxovirus that causes regular outbreaks in East Asia with mortality rate exceeding 75%. Major cellular targets of NiV infection are endothelial cells and neurons. To better understand virus-host interaction, we analyzed the transcriptome profile of NiV infection in primary human umbilical vein endothelial cells. We further assessed some of the obtained results by in vitro and in vivo methods in a hamster model and in brain samples from NiV-infected patients. We found that NiV infection strongly induces genes involved in interferon response in endothelial cells. Among the top ten upregulated genes, we identified the chemokine CXCL10 (interferon-induced protein 10, IP-10), an important chemoattractant involved in the generation of inflammatory immune response and neurotoxicity. In NiV-infected hamsters, which develop pathology similar to what is seen in humans, expression of CXCL10 mRNA was induced in different organs with kinetics that followed NiV replication. Finally, we showed intense staining for CXCL10 in the brain of patients who succumbed to lethal NiV infection during the outbreak in Malaysia, confirming induction of this chemokine in fatal human infections. This study sheds new light on NiV pathogenesis, indicating the role of CXCL10 during the course of infection and suggests that this chemokine may serve as a potential new marker for lethal NiV encephalitis

Epinephrine Versus Norepinephrine for Cardiogenic Shock After Acute Myocardial Infarction

BACKGROUND Vasopressor agents could have certain specific effects in patients with cardiogenic shock (CS) after myocardial infarction, which may influence outcome. Although norepinephrine and epinephrine are currently the most commonly used agents, no randomized trial has compared their effects, and intervention data are lacking. OBJECTIVES The goal of this paper was to compare in a prospective, double-blind, multicenter, randomized study, the efficacy and safety of epinephrine and norepinephrine in patients with CS after acute myocardial infarction. METHODS The primary efficacy outcome was cardiac index evolution, and the primary safety outcome was the occurrence of refractory CS. Refractory CS was defined as CS with sustained hypotension, end-organ hypoperfusion and hyperlactatemia, and high inotrope and vasopressor doses. RESULTS Fifty-seven patients were randomized into 2 study arms, epinephrine and norepinephrine. For the primary efficacy endpoint, cardiac index evolution was similar between the 2 groups (p = 0.43) from baseline (H0) to H72. For the main safety endpoint, the observed higher incidence of refractory shock in the epinephrine group (10 of 27 [37%] vs. norepinephrine 2 of 30 [7%]; p = 0.008) led to early termination of the study. Heart rate increased significantly with epinephrine from H2 to H24 while remaining unchanged with norepinephrine (p <0.0001). Several metabolic changes were unfavorable to epinephrine compared with norepinephrine, including an increase in cardiac double product (p = 0.0002) and lactic acidosis from H2 to H24 (p <0.0001). CONCLUSIONS In patients with CS secondary to acute myocardial infarction, the use of epinephrine compared with norepinephrine was associated with similar effects on arterial pressure and cardiac index and a higher incidence of refractory shock. (Study Comparing the Efficacy and Tolerability of Epinephrine and Norepinephrine in Cardiogenic Shock [OptimaCC]; NCT01367743) (J AmColl Cardiol 2018; 72: 173-82) (C) 2018 by the American College of Cardiology Foundation.Peer reviewe

Prevalence of impairments, disabilities, handicaps and quality of life in the general population: a review of recent literature

International audienc

Global perturbation of stratospheric water and aerosol burden by Hunga eruption

The eruption of the submarine Hunga volcano in January 2022 was associated with a powerful blast that injected volcanic material to altitudes up to 58 km. From a combination of various types of satellite and ground-based observations supported by transport modeling, we show evidence for an unprecedented increase in the global stratospheric water mass by 13% relative to climatological levels, and a 5-fold increase of stratospheric aerosol load, the highest in the last three decades. Owing to the extreme injection altitude, the volcanic plume circumnavigated the Earth in only 1 week and dispersed nearly pole-to-pole in three months. The unique nature and magnitude of the global stratospheric perturbation by the Hunga eruption ranks it among the most remarkable climatic events in the modern observation era, with a range of potential long-lasting repercussions for stratospheric composition and climate

Analyse des mécanismes d'action des traitements de carter dans les compresseurs axiaux

Ce travail de thèse, mené dans le cadre d’une convention CIFRE entre Snecma, le CERFACS et le LMFA, s’inscrit dans un contexte d’amélioration des performances et d’extension de la plage de fonctionnement des compresseurs de type axial équipant les turboréacteurs. L’une des principales difficultés rencontrée dans cette démarche concerne la maîtrise des écoulements dans la zone de jeu en tête des aubes rotors et qui peuvent entraîner une perte de stabilité du système (pompage et décollement tournant).Une solution technologique prometteuse pour améliorer la stabilité est le traitement de carter qui consiste en un dispositif passif complexe de fentes implantées au carter au droit des rotors. En vue d’en améliorer sa conception, les travaux de thèse visent plus particulièrement à approfondir la compréhension des mécanismes d’action grâce à une approche numérique CFD avec le code elsA développé par l’ONERA et le CERFACS, en modélisation stationnaire et instationnaire. Ces travaux s’articulent autour de trois axes principaux. Le premier a eu pour objectif de développer un outil numérique d’aide à la compréhension des mécanismes d’action des traitements de carter et de diagnostic de leur efficacité. Le principe de l’outil, qui est une extension du modèle initialement proposé par Shabbir et Adamczyk, repose sur une évaluation des contributions des termes des équations de Navier-Stokes stationnaires et instationnaires sur un volume de contrôle pris dans l’écoulement. Dans le cas pratique, cela revient à quantifier les efforts appliqués sur le fluide. Le second axe traite de l’analyse des mécanismes d’action des traitements de carter axisymétriques dans deux compresseurs axiaux : l’un subsonique à carter cylindrique (CREATE) et l’autre transsonique à carter conique (NASA Rotor 37). Les enseignements de cette étude indiquent que ce type de géométrie est marqué par son effet d’aspiration de fluide dans la veine. Ce mécanisme est d’autant plus amplifié par un phénomène d’interaction complexe des fentes avec l’écoulement de jeu et la proximité de l’intrados de l’aube adjacente. Cette partie s’est également attardé à la réponse des rainures à un phénomène instationnaire de type sillage de roue amont. Les résultats ont montré que les fentes amortissent les fluctuations de gradient de pression adverse. Le troisième axe porte sur l’analyse des mécanismes des traitements de carter non-axisymétriques à travers l’étude numérique d’un cas test transsonique à carter cylindrique (CBUUA). Le mécanisme d’action améliorant la stabilité de la machine tient en la capacité des fentes à limiter la migration dans la direction circonférentielle du vortex de jeu. Les résultats montrent que ce type de géométrie est caractérisé par son effet de réinjection d’air qui vient ré-énergétiser l’écoulement proche carter.This thesis work, conducted as part of a CIFRE agreement between Snecma, CERFACS and LMFA, deals with the context of improving performance and extending the operating range of axial compressors fitted turbojets. One of the main difficulties in this approach is the flow control in the rotor tip region, which can cause the loss of the system stability (surge and rotating stall). A promising technology known to bring substantial stability is the casing treatment. This passive control device consists of slots of complex geometry within the rotor casing. In order to improve its design, the thesis aimed specifically at improving the understanding of their mechanisms through a numerical approach using the CFD code elsA developed by ONERA and CERFACS, with steady and unsteady approaches. This work focused on three main axes. The first concerns the development of a numerical tool to support the understanding of casing treatment mechanisms and the diagnosis of their efficiency. The principle of the tool, which is an extension of the model originally proposed by Shabbir and Adamczyk, is based on an assessment of the contributions of the terms of the steady and unsteady Navier-Stokes equations on a control volume taken in the flow. In practice, this permits to quantify the forces applied to the fluid. The second axis deals with the analysis of the flow mechanisms induced by axisymetric casing treatments in two axial compressors : one subsonic with a cylindrical casing (CREATE) and the other transonic with a conical casing (NASA Rotor 37). The findings of this study indicate that this type of geometry is characterized by its bleeding effect. This mechanism is further amplified by a complex phenomenon of interaction between grooves, tip leakage vortex and the proximity to the pressure side of the adjacent blade. This part has also dwelt on the groove’s response to unsteady upstream stator wakes. The results showed that the slots are able to damp fluctuations of adverse pressure gradient. The third area concerns the analysis of the flow mechanisms induced by non-axisymmetric casing treatment through the numerical study of a transonic compressor with cylindrical casing (CBUUA). The mechanism leading to an enhancement of the stability results in slots ability to limit the migration in the circumferential direction of the tip leakage vortex. The results show that this type of geometry is characterized by its effect of re-injection of fluid that comes re-energize the near casing flow

Numerical analysis of the tip leakage flow field in a transonic axial compressor with circumferential casing treatment

International audienc

Comment on “Finding finite-time invariant manifolds in two-dimensional velocity fields” [Chaos 10 , 99 (2000)]

International audienc