Experimental investigation of cavitating flow in 2D and 3D transparent diesel nozzle models

International audienceThe paper describes two experimental setup dedicated to the study of cavitation in diesel injectors. The two experimental setup are described and preliminary results are presented. The first approach consists of flow characterization in 3D and real-size transparent injector. A second approach deals with a 2D injector and is dedicated to the specific study of surface roughness effect on cavitation processes

Optical investigation of a cavitating flow in a 2D nozzle

International audienceIn heat engines (vehicle), cavitation plays an important role in fuel atomization mechanisms. The physics of cavitation as well as its impact on spray formation and injector efficiency are not well documented yet. Experimental investigations are required. The complexity of modern injectors and the extreme conditions of injection do not facilitate experimental investigations. In this paper, experiments are conducted in a simplified geometry. The model nozzle consists of a transparent 2D micro-channel supplied with a test-oil (ISO 4113). Velocity fields are obtained by means of a shadowgraph-like imaging arrangement using PIV components (double pulsed laser and double-frame camera). Pressure fields are obtained by interferometry coupled with a Schlieren technique

Cavitation dans un micro-canal modèle d'injecteur diesel (méthodes de visualisation et influence de l'état de surface)

Ce travail de thèse repose sur l élaboration et l exploitation d un banc expérimental dédié à l étude d un écoulement cavitant dans un micro-canal, pour des conditions proches de celles de l injection diesel. Ce banc a été développé dans le but de faire varier différents paramètres, notamment l état de surface des parois du canal. Plusieurs méthodes optiques (imagerie en transmission, strioscopie et interférométrie) ont été mises en place afin de visualiser l écoulementet d en extraire des informations quantitatives. Les images en transmission permettent de visualiser la formation de vapeur dans le canal. Elles sont sensibles au gradient de masse volumique et font ainsi apparaître des couches de cisaillement, des structures turbulentes et des ondes de pression. Leur interprétation est rendue délicate par cette richesse en information et nécessite de recourir aux autres techniques optiques. Il ressort de ce travail que la cavitation se forme dans la couche de cisaillement, sous l effet combiné de la dépression engendrée par le décollement à l entrée du canal et de tourbillons générés par des instabilités dans la couche de cisaillement. La confrontation des résultats obtenus à l aide des différentes techniques optiques, notamment les champs de pression reconstruits à partir des interférogrammes, montre que la zone de formation de la cavitation ne correspond pas à la zone de minimum de pression moyenne de l écoulement. Il apparaît aussi que certaines bulles de vapeur ont une durée de vie bien supérieure à ce que prévoient les modèles de dynamique de bulles. On suspecte que des fluctuations de pression de l ordre de 20 bar, associées à la turbulence, contribuent à la prolongation de ces temps de vie. Un algorithme de PIV, appliqué à des couples d images en transmission, permet de montrer une augmentation importante des fluctuations de vitesse en sortie de canal lorsque les poches de vapeur se développent. Cette augmentation devient plus significative quand les poches atteignent60% de la longueur du canal. L écoulement cavitant est essentiellement piloté par le nombre de cavitation K. Les conditions d apparition et de développement de la cavitation ont été quantifiées dans différents canaux, en faisant varier des paramètres géométriques, la pression amont ou la température. L influence de la hauteur du canal et du rayon de courbure à l entrée de l orifice est conforme aux données de la littérature. Une dépendance du nombre de cavitation critique Kcrit à l apparition de la cavitation au nombre de Reynolds Re est montrée. Enfin, l influence de l état de surface des parois a fait l objet d une étude spécifique. Cette partie du travail demande probablement à être complétée mais l état de surface semble avoir une influence sur la cavitation. D après les cas étudiés au cours de cette thèse, une surface rugueuse ou texturée avec des motifs suffisamment espacés peut retarder l apparition de la cavitation et une rugosité limitée (jusqu à Ra = 0,7 mici) peut favoriser le développement des poches de vapeur.This PhD study is based on the design and use of an experimental set-up dedicated to the study of a cavitating flow in a micro-channel in conditions close to Diesel injection. The experimental set-up has been designed so that different parameters may vary, in particular channel wall roughness. Several optical systems (backlit imaging, Schlieren imaging and interferometry) have been developed in order to visualize the flow and get quantitative data.Backlit images make it possible to visualize vapor formation in the channel. They are sensitive to density gradients and therefore show shear layers, turbulent structures as well as pressure waves. Since they are rich in information, it is tricky to interpret them and the use of other optical methods is required.This study shows that cavitation appears in the shear layer due to the combined effect of the depression induced by flow detachment at the channel inlet and vortexes caused by instabilities in the shear layer. The comparison of the results obtained from the different optical systems in particular the pressure fields rebuilt from interferograms indicates that cavitation does not appear where flow pressure is the lowest in average.It is noticed that some vapor bubbles have a life expectancy much higher than predicted by bubble dynamics models. It is thought that pressure variations of about 20 bar, associated to turbulence, may play a role in this phenomenon.A PIV algorithm applied to couples of backlit images shows that velocity fluctuations largely increase at the channel outlet when vapor cavities develop. The increase gets more significant when cavities are 60 % the channel length.The cavitating flow is mainly dependent on the cavitation number K. The conditions of cavitation inception and development have been quantified in different channels, and geometrical parameters, upstream pressure or temperature have varied. The influence of channel height and radius inlet on cavitation is in line with the literature. At cavitation inception, it is shown that the critical cavitation number Kcrit is dependent on Reynolds number Re. Finally, the influence of wall roughness has been the subject of a specific study. Although it would need to be further investigated, roughness seems to have an influence on cavitation. The samples used during this PhD work suggest that roughness or patterns sufficiently spaced out may delay cavitation inception, and limited roughness (up to Ra = 0.7 m here) may enhance vapor cavity development.LYON-Ecole Centrale (690812301) / SudocSudocFranceF

A Type I and Type II microsatellite linkage map of Rainbow trout (Oncorhynchus mykiss) with presumptive coverage of all chromosome arms

BACKGROUND: The development of large genomic resources has become a prerequisite to elucidate the wide-scale evolution of genomes and the molecular basis of complex traits. Linkage maps represent a first level of integration and utilization of such resources and the primary framework for molecular analyses of quantitative traits. Previously published linkage maps have already outlined the main peculiarities of the rainbow trout meiosis and a correspondance between linkage groups and chromosome arms has been recently established using fluorescent in situ hybridization. The number of chromosome arms which were covered by these maps remained unknown. RESULTS: We report an updated linkage map based on segregation analysis of more than nine hundred microsatellite markers in two doubled haploid gynogenetic lines. These markers segregated into 31 linkage groups spanning an approximate total map length of 2750 cM. Centromeres were mapped for all the linkage groups using meiogenetic lines. For each of the 31 linkage groups, the meta or acrocentric structure infered from centromere mapping was identical with those recently found with fluorescent in situ hybridization results. The present map is therefore assumed to cover the 52 chromosome arms which constitute the rainbow trout karyotype. Our data confirm the occurrence of a high interference level in this species. Homeologous regions were identified in eleven linkage groups, reflecting the tetraploid nature of the salmonid genome. The data supported the assumption that gene orders are conserved between duplicated groups and that each group is located on a single chromosome arm. Overall, a high congruence with already published rainbow trout linkage maps was found for both gene syntenies and orders. CONCLUSION: This new map is likely to cover the whole set of chromosome arms and should provide a useful framework to integrate existing or forthcoming rainbow trout linkage maps and other genomic resources. Since very large numbers of EST containing microsatellite sequences are available in databases, it becomes feasible to construct high-density linkage maps localizing known genes. This will facilitate comparative mapping and, eventually, identification of candidate genes in QTL studies

Resistance to a Rhabdovirus (VHSV) in Rainbow Trout: Identification of a Major QTL Related to Innate Mechanisms

Chantier qualité GAHealth control is a major issue in animal breeding and a better knowledge of the genetic bases of resistance to diseases is needed in farm animals including fish. The detection of quantitative trait loci (QTL) will help uncovering the genetic architecture of important traits and understanding the mechanisms involved in resistance to pathogens. We report here the detection of QTL for resistance to Viral Haemorrhagic Septicaemia Virus (VHSV), a major threat for European aquaculture industry. Two induced mitogynogenetic doubled haploid F2 rainbow trout (Oncorhynchus mykiss) families were used. These families combined the genome of susceptible and resistant F0 breeders and contained only fully homozygous individuals. For phenotyping, fish survival after an immersion challenge with the virus was recorded, as well as in vitro virus replication on fin explants. A bidirectional selective genotyping strategy identified seven QTL associated to survival. One of those QTL was significant at the genome-wide level and largely explained both survival and viral replication in fin explants in the different families of the design (up to 65% and 49% of phenotypic variance explained respectively). These results evidence the key role of innate defence in resistance to the virus and pave the way for the identification of the gene(s) responsible for resistance. The identification of a major QTL also opens appealing perspectives for selective breeding of fish with improved resistance

Bourdieusian Reflections on Language: Unavoidable Conditions of the Real Speech Situation

The main purpose of this paper is to shed light on Pierre Bourdieu’s conception of language. Although he has dedicated a significant part of his work to the study of language and even though his analysis of language has been extensively discussed in the literature, almost no attention has been paid to the factthat Bourdieu’s account of language is based on a number of ontological presuppositions, that is, on a set of universal assumptions about the very nature of language. This article aims to fill this gap in the literature by offering a detailed overview of 10 key features which, from a Bourdieusian point of view, can be regarded as inherent in language. On the basis of this enquiry,the study seeks todemonstrate that——contraryto commonbelief——there is not only a Bourdieusian sociology of language but also a Bourdieusian philosophy of language, which provides a useful theoretical framework for examining the unavoidable conditions of the real speech situation. The paper draws to a close by reflecting on the flaws and limitations of Bourdieu’s approach to language

Frantoio

Frantoio est en Méditerranée. Frantoio est à Mazara del Vallo - en Sicile. Frantoio est isolé de la mer touristique par la voie ferrée. Frantoio est en milieu suburbain. Frantoio est protégé du reste du monde par un mur technologique. Frantoio a un objectif social. Frantoio est un miroir. Frantoio est un écosystème. Frantoio est un oasis. Frantoio est un frantoio - un moulin à huile d’olive. Frantoio comprend un restaurant. Frantoio a un toit-terrasse. Frantoio est une oliveraie. Frantoio est une orangeraie. Frantoio est un parc. Frantoio n’est pas nostalgique. Frantoio a une faible empreinte carbone. Frantoio est une proposition territoriale. Frantoio comprend un programme de plantation d’oliviers pour les parcelles en friche. Frantoio est un réseau de parcelles agricoles. Frantoio est un ensemble d’espaces publics. Frantoio intègre une fontaine à pivot central. Frantoio accélère la spontanéité. Frantoio propose la flânerie, le partage. Frantoio favorise l’entretien du corps et de l’esprit. Frantoio organise annuellement la Sagra delle Olive. Frantoio comprend le Club, la Pépinière et le Kiosque solaire. Frantoio est un ensemble étrange. Frantoio est un ensemble familier. Frantoio est un scénario méditerranéen

Étude d'un écoulement de canal cavitant par plusieurs techniques optiques

International audienceLa cavitation joue un rôle important dans les injecteurs automobiles et a fait l'objet de nombreuses études expérimentales. Des modèles numériques existent mais nous manquons de résultats expérimentaux précis et complets pour les faire progresser et les valider. L'objectif de ce travail est de réaliser des observations et des mesures dans un écoulement 2D cavitant, dans des conditions proches de celles de l'injection diesel. Différentes techniques optiques ont été utilisées pour visualiser les poches de cavitation et accéder au champ de pression. La formation et le développement de poches de cavitation sont observés par imagerie en transmission. La technique révèle également la présence de gradients de densité dans l'écoulement, ce qui enrichit les observations mais engendre des difficultés d'interprétation. Un couplage entre imagerie interférométrique et strioscopie permet d'obtenir en complément des champs de densité dans le canal. Mots Clés : Injection diesel / Cavitation / Imagerie en transmission / Interférométrie / Strioscopi

Experimental Investigation of Roughness Effects on Cavitating Flow in Diesel Injectors

International audienceIn diesel injectors, the wall roughness of the nozzle holes is thought to influence cavitation formation during the injection cycle. In order to highlight the roughness effect, an experimental setup has been designed. This setup consists of a 2D-orifice that confines a cavitating flow. Specific tools are used to control-by means of femtosecond laser-and finely characterise wall roughness, and the cavitating flow is visualised using optical techniques. The different devices are introduced and the first results are presented

Experimental investigation of cavitating flow in 2D and 3D transparent diesel nozzle models

International audienceThe paper describes two experimental setup dedicated to the study of cavitation in diesel injectors. The two experimental setup are described and preliminary results are presented. The first approach consists of flow characterization in 3D and real-size transparent injector. A second approach deals with a 2D injector and is dedicated to the specific study of surface roughness effect on cavitation processes