Modèle thermo-mécanique avec couplage fort du carter et de l'abradable pour les interactions rotor/stator

International audienceModern turbomachine designs feature reduced nominal clearances between rotating bladed-disks and their surrounding casings in order to improve the engine efficiency. Unavoidably, clearance reduction increases the risk of contacts between static and rotating components which may yield hazardous interaction phenomena. In this context, the deposition of an abradable coating along the casing inner surface is a common way to enhance operational safety while mitigating interaction phenomena thus allowing for tighter clearances. Nonetheless, interactions leading to unexpected wear removal phenomena between a bladed-disk and a casing with abradable coating have been observed experimentally. Beside of blade damages such as cracks resulting from high amplitudes of vibration, experimental observations included very significant temperatures increase, particularly within the abradable coating, to a point that thermo-mechanical effects may not be neglected anymore. The aim of this work is to investigate the numerical modeling of thermal effects in the abradable coating and the casing due to contact interactions. In particular, the proposed model provides insight on the sensitivity of engines to contact events when the plane had reduced tarmac times between two consecutive flights. A strongly coupled thermo-mechanical model of the casing and its abradable coating is first described. A 3D cylindrical mesh is employed, it may be decomposed in two parts: (1) along the casing contact surface, a cylindrical thermal mesh is constructed to compute the temperature elevation and heat diffusion in the three directions of space within the abradable coating, and (2) the casing itself is represented by a simplified cylindrical thermo-mechanical mesh to compute both temperature elevation and the induced deformations following temperature changes. This 3D hybrid mesh is combined with a mechanical mesh of the abradable layer, dedicated to wear modeling and the computation of normal and tangential contact forces following blade/abradable coating impacts. The heat flux resulting from contact events is related to the friction forces and only heat transfer by conduction is considered in this work. In order to reduce computational times, the time integration procedure is twofold: the explicit time integration scheme featuring reduced time steps required for contact treatment is combined with a larger time step time integration scheme used for the casing thermo-mechanical model. An extensive validation procedure is carried out from a numerical standpoint, it underlines the convergence of the model with respect to time and space parameters.Les conceptions de turbomachines modernes présentent des jeux nominaux réduits entre les disques aubagés tournants et leurs carters environnants afin d'améliorer l'efficacité du moteur. Inévitablement, la réduction des jeux augmente le risque de contacts entre les composants statiques et tournants, qui peuvent menerà des phénomènes d'interaction dangereux. Dans ce contexte, le dépôt d'un revêtement abradable sur la surface intérieure du carter est une manière usuelle d'améliorer la sécurité en fonctionnement en atténuant les phénomènes d'interaction, et donc permettant des jeux réduits. Néanmoins, des interactions entre un disque aubagé et un carter avec un revêtement abradable menantà des phénomènes d'usure inattendue ontété observées expérimentalement. Hormis les dommages d'aubes tels que les fissurations résultant de grandes amplitudes de vibration, les observations expérimentales incluent une augmentation très significative des températures, particulièrement dans le revêtement abradable,à tel point que les effets thermo-mécaniques ne pourraient plusêtre négligés. Le but de ce travail est d'investiguer la modélisation numérique des effets thermiques dans le revêtement abradable et le carter suite des interactions de contact. En particulier, le modèle proposé fournit un aperçu de la sensibilité des moteurs auxévènements de contact quand l'avion a un temps réduit sur le tarmac entre deux vols consécutifs. Un modèle thermo-mécanique fortement couplé du carter et de son revêtement abradable est premièrement décrit. Un maillage cylindrique 3D est utilisé, il peutêtre décomposé en deux parties : (1) le long de la surface du carter, un maillage thermique cylindrique est construit pour calculer l'élévation de température et la diffusion de la chaleur dans les trois directions de l'espace dans la couche abradable, et (2) le carter lui-même est représenté par un maillage thermo-mécanique simplifié cylindrique pour calculer l'élévation de température et les déformations induites suite aux changements de températures. Ce maillage 3D hybride est combiné avec un maillage mécanique du revêtement abradable, dédiéà la modélisation de l'usure et au calcul des forces de contact normales et tangentielles suite aux impacts aube/abradable. Le flux de chaleur résultant des contacts est relié aux forces de frottement, et des transferts de chaleur par conduction uniquement sont considéré dans ce travail. Pour réduire les temps de calcul, la procédure d'intégration temporelle est double : un schéma d'intégration temporelle explicite ayant des pas de temps réduits requis pour le traitement du contact est combiné avec un schéma d'intégration temporelle avec des pas de temps plus grands utilisé pour le modèle thermo-mécanique du carter. Une procédure de validation extensive est menée d'un point de vue numérique, soulignant la convergence du modèle avec les paramètres temporels et spatiaux

L'affaire Séralini et la confiance dans l'ordre normatif dominant de la science

D’où vient la confiance dans la science ? Comment est-elle nourrie et renforcée? Dans un contexte où, au prétexte de la crise des finances publiques, les politiques scientifiques nationales semblent privilégier la voie du financement de la science par des partenariats avec le secteur privé, notamment la grande industrie, la confiance dans la science reste un argument majeur pour justifier le maintien ou même le renforcement du soutien de l’État à la recherche scientifique. L’enjeu de la confiance dans la science apparaît ainsi fondamentalement politique et non pas seulement éthique : une science inspirant confiance aux citoyens/contribuables pourra justifier son financement par les fonds publics, par la richesse collective

El caso Seralini y la confianza en el orden normativo dominante de la ciencia

¿De dónde viene la confianza en la ciencia?; ¿cómo se nutre y se refuerza? En un contexto en el que, bajo el pretexto de la crisis en las finanzas públicas, las políticas científicas nacionales parecen favorecer el camino del financiamiento de la ciencia a través de asociaciones con el sector privado, en particular con las grandes empresas industriales,1 la confianza en la ciencia sigue siendo el argumento principal para justificar el mantenimiento e incluso reforzar el apoyo gubernamental a la investigación. El tema de la confianza parece, así pues, ser fundamentalmente político y no sólo ético: una ciencia que inspira confianza en los ciudadanos-contribuyentes podrá justificar su financiamiento con fondos públicos, a través de la riqueza colectiva

Revisiting the role of friction coefficients in granular collapses: confrontation of 3-D non-smooth simulations with experiments

In this paper, transient granular flows are examined both numerically and experimentally. Simulations are performed using the continuous 3D granular model introduced in Daviet & Bertails-Descoubes (2016), which represents the granular medium as an inelastic and dilatable continuum subject to the Drucker-Prager yield criterion in the dense regime. One notable feature of this numerical model is to resolve such a non-smooth rheology without any regularisation. We show that this non-smooth model, which relies on a constant friction coefficient, is able to reproduce with high fidelity various experimental granular collapses over inclined erodible beds, provided the friction coefficient is set to the avalanche angle - and not to the stop angle, as generally done. In order to better characterise the range of validity of the fully plastic rheology in the context of transient frictional flows, we further revisit scaling laws relating the shape of the final collapse deposit to the initial column aspect ratio, and accurately recover established power-law dependences up to aspect ratios in the order of 10. The influence of sidewall friction is then examined through experimental and simulated collapses with varying channel widths. The effective flow thickness is estimated in relation to the channel width, thereby challenging previously held assumptions on its estimation. Finally, we discuss the potential extension of the constant coefficient model with a hysteretic model to refine predictions of early-stage collapse dynamics, illustrating the impact of such phenomenology on transient flows and paving the way to more elaborate analysis.Comment: 25 figures and 6 movie

Control of the Evolution of Iron Peroxide Intermediate in Superoxide Reductase from Desulfoarculus baarsii. Involvement of Lysine 48 in Protonation

International audienceSuperoxide reductase is a nonheme iron metalloenzyme that detoxifies superoxide anion radicals O(2)(•-) in some microorganisms. Its catalytic mechanism was previously proposed to involve a single ferric iron (hydro)peroxo intermediate, which is protonated to form the reaction product H(2)O(2). Here, we show by pulse radiolysis that the mutation of the well-conserved lysine 48 into isoleucine in the SOR from Desulfoarculus baarsii dramatically affects its reaction with O(2)(•-). Although the first reaction intermediate and its decay are not affected by the mutation, H(2)O(2) is no longer the reaction product. In addition, in contrast to the wild-type SOR, the lysine mutant catalyzes a two-electron oxidation of an olefin into epoxide in the presence of H(2)O(2), suggesting the formation of iron-oxo intermediate species in this mutant. In agreement with the recent X-ray structures of the peroxide intermediates trapped in a SOR crystal, these data support the involvement of lysine 48 in the specific protonation of the proximal oxygen of the peroxide intermediate to generate H(2)O(2), thus avoiding formation of iron-oxo species, as is observed in cytochrome P450. In addition, we proposed that the first reaction intermediate observed by pulse radiolysis is a ferrous-iron superoxo species, in agreement with TD-DFT calculations of the absorption spectrum of this intermediate. A new reaction scheme for the catalytical mechanism of SOR with O(2)(•-) is presented in which ferrous iron-superoxo and ferric hydroperoxide species are reaction intermediates, and the lysine 48 plays a key role in the control of the evolution of iron peroxide intermediate to form H(2)O(2)

Ecotoxicity tests and ecoscores to improve soil management : case of a secondary lead smelter plant

International audienceriginally located on the outskirts of cities, numerous industrial sites, sometimes abandoned, are now in urban areas and are therefore likely to have environmental and health risks to surrounding populations. Currently, rehabilitation of the sites frequently entails excavation of polluted soils. Excavated soils can thus follow two different ways: landfilling, expensive and energy intensive, or reuse/recycling, integrated to sustainable development. The choice of a specific track mainly depends on total and leachable concentrations of the pollutant in the soil. Among the numerous pollutants observed in urban and peri-urban areas, trace metals are often present in soils; atmosphere emissions by smelters being one of the main anthropogenic source. MTE speciation and compartmentalization in soils can modify their impact on living organisms

Invest Ophthalmol Vis Sci

PURPOSE: The purpose of this study was to compare 24-hour intraocular pressure (IOP) related fluctuations monitoring between 2 groups of visual field progression rates in patients with open angle glaucoma (OAG). METHODS: Cross-sectional study performed at Bordeaux University Hospital. Twenty-four-hour monitoring was performed using a contact lens sensor (CLS; Triggerfish; SENSIMED, Etagnières, Switzerland). Progression rate was calculated using a linear regression of the mean deviation (MD) parameter of the visual field test (Octopus; HAAG-STREIT, Switzerland). Patients were allocated into two groups: group 1 with an MD progression rate <-0.5 dB/year and group 2 with an MD progression rate ≥-0.5 dB/year. An automatic signal-processing program was developed and a frequency filtering of the monitoring by wavelet transform analysis was used to compare the output signal between the two groups. A multivariate classifier was performed for prediction of the faster progression group. RESULTS: Fifty-four eyes of 54 patients were included. The mean progression rate was -1.09 ± 0.60 dB/year in group 1 (n = 22) and -0.12 ± 0.13 dB/year in group 2 (n = 32). Twenty-four-hour magnitude and absolute area under the monitoring curve were significantly higher in group 1 than in group 2 (group 1: 343.1 ± 62.3 millivolts [mVs] and 8.28 ± 2.10 mVs, respectively, group 2: 274.0 ± 75.0 mV and 6.82 ± 2.70 mVs respectively, P < 0.05). Magnitude and area under the wavelet curve for short frequency periods ranging from 60 to 220 minutes were also significantly higher in group 1 (P < 0.05). CONCLUSIONS: The 24-hour IOP related fluctuations characteristics, as assessed by a CLS, may act as a risk factor for progression in OAG. In association with other predictive factors of glaucoma progression, the CLS may help adjust treatment strategy earlier

Ecotoxicity tests and ecoscores to improve soil management : case of a secondary lead smelter plant

International audienceriginally located on the outskirts of cities, numerous industrial sites, sometimes abandoned, are now in urban areas and are therefore likely to have environmental and health risks to surrounding populations. Currently, rehabilitation of the sites frequently entails excavation of polluted soils. Excavated soils can thus follow two different ways: landfilling, expensive and energy intensive, or reuse/recycling, integrated to sustainable development. The choice of a specific track mainly depends on total and leachable concentrations of the pollutant in the soil. Among the numerous pollutants observed in urban and peri-urban areas, trace metals are often present in soils; atmosphere emissions by smelters being one of the main anthropogenic source. MTE speciation and compartmentalization in soils can modify their impact on living organisms

Concomitant heterochromatinisation and down-regulation of gene expression unveils epigenetic silencing of RELB in an aggressive subset of chronic lymphocytic leukemia in males

<p>Abstract</p> <p>Background</p> <p>The sensitivity of chronic lymphocytic leukemia (CLL) cells to current treatments, both <it>in vitro </it>and <it>in vivo</it>, relies on their ability to activate apoptotic death. CLL cells resistant to DNA damage-induced apoptosis display deregulation of a specific set of genes.</p> <p>Methods</p> <p>Microarray hybridization (Human GeneChip, Affymetrix), immunofluorescent <it>in situ </it>labeling coupled with video-microscopy recording/analyses, chromatin-immunoprecipitation (ChIP), polymerase chain reactions (PCR), real-time quantitative PCR (RT-QPCR) and bisulfite genome sequencing were the main methods applied. Statistical analyses were performed by applying GCRMA and SAM analysis (microarray data) and Student's t-test or Mann & Whitney's U-test.</p> <p>Results</p> <p>Herein we show that, remarkably, in a resistant male CLL cells the vast majority of genes were down-regulated compared with sensitive cells, whereas this was not the case in cells derived from females. This gene down-regulation was found to be associated with an overall gain of heterochromatin as evidenced by immunofluorescent labeling of heterochromatin protein 1α (HP-1), trimethylated histone 3 lysine 9 (3metH3K9), and 5-methylcytidine (5metC). Notably, 17 genes were found to be commonly deregulated in resistant male and female cell samples. Among these, <it>RELB </it>was identified as a discriminatory candidate gene repressed in the male and upregulated in the female resistant cells.</p> <p>Conclusion</p> <p>The molecular defects in the silencing of <it>RELB </it>involve an increase in H3K9- but not CpG-island methylation in the promoter regions. Increase in acetyl-H3 in resistant female but not male CLL samples as well as a decrease of total cellular level of RelB after an inhibition of histone deacetylase (HDAC) by trichostatin A (TSA), further emphasize the role of epigenetic modifications which could discriminate two CLL subsets. Together, these results highlighted the epigenetic <it>RELB </it>silencing as a new marker of the progressive disease in males.</p