Transferts de chaleur et de masse dans de ecoulements turbulents de Taylor-Couette avec flux axial

International audienceNous nous intéressons ici aux transferts de chaleur et de masse dans unsys eme de Taylor-Couette avec flux axial. Un dispositif permettant des mesures de vitesse et de coefficients de transferts á eté développé. Les régime etudiés sont turbulents : nombre de Reynolds axial entre 5600 et 11200 et entre 7900 et 79 millios pour le nombre de Taylor. Nous reportons le nombre de Nusselt en fonction du nombre de Reynolds axial et du nombre de Taylor ainsi que des mesures de vitesse. La présence de structures organisées proche du rotor á eté observée, ce qui est confirmé par un calcul DNS

Early innervation of skeletal muscle during tail regeneration in urodele amphibians

The innervation pattern of skeletal muscles was studied in the normal and regenerating tail of Notophthalmus viridescens . Silver staining for nerve endings and histochemical localization of acetylcholinesterase (AChE) were used for light microscopy. In normal musculature, AChE positive reactions were localized at the ends of the muscle fibers where they are anchored on connective tissue septa by myotendinous junctions. At this level, silver staining shows nerve terminals forming endplates. During regeneration, positive reactions for AChE appear de novo as dense plates localized at the ends of the newly formed myotubes. The mechanisms involved in the localization of AChE on this surface seem to operate before previous local contacts by nerve terminals. From the ultrastructural data and immunohistochemical results with anti-laminin antibody, these observations suggest that regenerating muscle fibers determine a region of post-synaptic specialization in close relation with the organization of myotendinous regions and basement membrane formation. Nerve-muscle contacts appear at these levels at stage IV (15–20 days after amputation) in the stump and in the rostral part of the regenerate (transition zone). These nerve terminals are provided by the disorganized peripheral nervous system of the injured segment. In the regenerate a similar pattern of AChE reaction can be seen in every myotube, differentiating according to a rostro-caudal gradient. Innervation at the ends of the muscle fibers is in spatiotemporal relation with the exits of the ventral roots from the regenerating nerve cord as the regenerate continues to grow in length.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38098/1/1402600310_ftp.pd

Smart pressure distribution estimation in biological joints for mechanical bio-inspired design

International audienceDesigning new mechanical links using bio-inspiration requires the knowledge of operating contact pressure in biological joints. However, the contact pressure magnitude and distribution are difficult to measure experimentally without disrupting the functioning of the articulation. In this paper, a new methodology to estimate the pressure distribution in biological joints is presented. A robust finite element model was developed based on in-vitro precise measurements of shapes, relative positions and loads in order to get accurate results. Furthermore, the envelope of the contact area was obtained through thermal imaging for comparison with the numerical results and qualitative validation of the FE model. Biologically inspired design, Finite element method, Mechanical connectio

Transferts de chaleur et de masse dans des écoulements turbulents de Taylor-Couette avec flux axial

Les écoulements tournants constituent une problématique récurrente dans le domaine industriel, notamment lorsqu’y est associée une finalité de refroidissement. Nous nous intéressons ici à un dispositif de Taylor-Couette avec flux axial forcé et gradients thermiques. Dans l’optique d’améliorer la compréhension des mécanismes de transferts de chaleur dans un tel système, nous avons adopté une démarche à la fois expérimentale et de simulation numérique. Un banc d’essais a été réalisé à l’IRPHE et permet des mesures de coefficients d’échange pariétal entre un rotor chauffé à flux constant et un écoulement axial forcé. Parallèlement à cela, des simulations numériques avec des codes de recherche et des logiciels commerciaux ont été effectuées au M2P2, sur un cas bien documenté, puis ensuite sur une géométrie similaire à celle de l’expérience. Le rotor est un cylindre en cuivre (16 cm de diamètre, 50 cm de long), équipé de 4 sondes PT100. Un fil chauffant placé à l’intérieur permet de générer un flux de chaleur de 1500 W. Un second cylindre, placé dans une enceinte thermalisée, est positionné concentriquement. On définit ainsi une cavité de rapport d’aspect 50 et de rapport des rayons 8/9 dans laquelle un écoulement d’eau circule à débit constant. Les nombres de Reynolds axiaux se situent entre 5000 et 11000. Les taux de rotation correspondent à des nombres de Taylor allant jusqu’à 70 millions. La température de l’eau est mesurée en entrée et sortie de la cavité à l’aide de sondes PT 100. Nous reportons l’évolution du nombre de Nusselt pariétal en fonction des nombres de Reynolds axial, de Taylor et de Prandtl. Des mesures par LDV (2C), puis par PIV (2D 3C) ont mis en évidence la structure de l’écoulement et notamment la présence de structures organisées le long du rotor, ce qui est confirmé par les calculs DNS

Heat and Mass Transfer in turbulent Taylor-Couette flows with an axial throughflow

International audienceIn the present work, we investigate the heat and mass transfer in the rotor-stator gap of an electrical motor modeled by a Taylor-Poiseuille system with an axial throughflow. An experimental set-up has been recently developed and enables to perform velocity and heat transfer measurements. The axial Reynolds number Re and the Taylor number Ta reach the values 11200 and 79 millions respectively so that the flow is turbulent. Velocity measurements are performed by LDV, PIV and Stereo-PIV. They highlight in particular the presence of coherent structures within the rotor boundary layer, whichis confirmed by a DNS calculation. The measured values of the Nusselt number are found to be proportional to the rotor boundary layer thickness to the power −1/10

Quaternary magnetic and oxygen isotope stratigraphy in diatom-rich sediments of the southern Gardar Drift (IODP Site U1304, North Atlantic)

The sediment sequence from Integrated Ocean Drilling Program (IODP) Site U1304 (53 degrees 03.40'N, 33 degrees 31.78'W; water depth, 3024 m) on the southern Gardar Drift, North Atlantic Ocean, covers the last similar to 1.8 Myr with a mean sedimentation rate of similar to 15 cm/kyr. At Site U1304, paleomagnetic directional and relative paleointensity (RPI) records have been generated for the last similar to 1.5 Myr, and benthic oxygen isotope data for the last similar to 1 Myr. The age model for Site U1304 was established by matching 6180 and RPI data to calibrated reference records. Prominent intervals of diatom mats at Site U1304 are associated with the latter stages of interglacial marine isotope stages (MIS) 9, 11, 13, 15, 21, 27 and 35, and with the weak glacial of MIS 14. The deposition of diatom mats, and associated diluted magnetic mineral concentrations, leads to weak magnetizations and susceptibilities in these intervals. Comparison of histograms of paleomagnetic directions and RPI from diatom-rich sediments and from surrounding silty clays indicates that, although results from diatom-rich sediments are more scattered, the occurrence of diatom mats does not appreciably distort the paleomagnetic directional and RPI records. Site 01304 sediments record the Matuyama/Brunhes boundary (similar to 772 ka), the Jaramillo Subchron (similar to 993-1071 ka) and the Cobb Mountain Subchron (similar to 1193-1219 ka), as well as three apparent geomagnetic excursions in the Matuyama Chron, interpreted as the "Kamikatsura/Santa Rosa", "Punaruu", and "Gardar" excursions, at similar to 888 ka, similar to 1124 ka, and similar to 14631 a, respectively. The Site U1304 RPI record can be correlated with the PISO-1500 RPI stack and with other high-resolution RPI records from the North Atlantic Ocean. Wavelet analyses performed on the Site U1304 RPI record and a new high-resolution North Atlantic paleointensity stack for the last 1500 kyr (HINAPIS-1500), comprising Ocean Drilling Program (ODP) Sites 983, 984 and IODP Sites U1306 and 01304, did not reveal significant orbital power

CH4 and δ18O of O2 records from Antarctic and Greenland ice: A clue for stratigraphic disturbance in the bottom part of the Greenland Ice Core Project and the Greenland Ice Sheet Project 2 ice cores

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Short- and Mid-Term Outcomes of Endovascular Stenting for the Treatment of Post-Thrombotic Syndrome due to Iliofemoral and Caval Occlusive Disease: A Multi-Centric Study from the French Society of Diagnostic and Interventional Cardiovascular Imaging (SFICV)

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