Novel Blade Design Strategy to Control the Erosion Aggressiveness of Cavitation

With the reduction in size of turbomachinery systems, cavitation aggressiveness is intensified. Erosion, caused by the repeated collapse of gaseous bubbles in proximity to solid surfaces, occurs at rates that dramatically downgrade the life expectancy of rotating parts. As a result, the compacting strategy, meant to reduce cost and improve efficiency, fails for liquid flows. The research undertaken here proposes a novel design method aimed at controlling the erosion aggressiveness of cavitation. The underlying idea is that the cavity closure shock is a determining factor in the intensity of bubble collapse mechanisms: sharp and high amplitude shocks give rise to strong erosion, while low gradient and low amplitude recoveries reduce the erosive intensity. The working hypothesis is tested here, first, by developing a novel inverse design algorithm capable of handling cavitating flow. The code solves the inviscid Euler equations and models blade cavitation using the Tohoku-Ebara barotropic equation of state. Bespoke preconditioning and multigrid procedures are constructed to handle the large amplitudes in flow regime (from hypersonic in the cavity to very low Mach number in the liquid phase). The inverse solver is then used to produce a set of 2D cascade hydrofoil geometries with smoothed shock profiles at cavity closure. The blades are assessed numerically using both steady state and time-resolved approaches. Both hydrodynamic performance, given in terms of swirl, lift and drag, and cavitation dynamics are evaluated. Recently developed erosion prediction methodologies are implemented and demonstrate compelling correlations between the erosion patterns and shock profile. Finally, experimental testing is carried out using a purposefully developed observation platform. The erosive performance of two of the geometries is measured using the paint removal technique. Results reveal a significant improvement in erosive response for the shock smoothed design, thus confirming the numerical findings as well as the validity of the design hypothesis

Existence and regularity of optimal shapes for spectral functionals with Robin boundary conditions

We establish the existence and find some qualitative properties of open sets that minimize functionals of the form $F(\lambda_1(\Omega;\beta),\dots,\lambda_k(\Omega;\beta))$ under measure constraint on $\Omega$, where $\lambda_i(\Omega;\beta)$ designates the $i$-th eigenvalue of the Laplace operator on $\Omega$ with Robin boundary conditions of parameter $\beta>0$. Moreover, we show that minimizers of $\lambda_k(\Omega;\beta)$ for $k\geq 2$ verify the conjecture $\lambda_k(\Omega;\beta)=\lambda_{k-1}(\Omega;\beta)$ in dimension three and more

Ode Hébraïque de Joseph de Meyrargues au pape Clément XIV. Carpentras ca. 1774

The study of the intellectual life of Avignonese and Comtadine Jews remains a desideratum for the scientific research which this paper contributes to with two unpublished liturgical songs. One of them is a canticle (the Ben Zvi Institute in Jerusalem, MS 1774), written in 1774 in honour of the Pope Clement XIV, Lorenzo Ganganelli, -who was remarkably favourable to the Jews, that reveals the life and work of a cantor in the synagogue of Carpentras, Joseph de Meyrargues, author of that poem and other poetical compositions. Another of these compositions is also published here for the first time according to the MS 2610 kept in the Carpentras Inguimbertine Library.El estudio de la vida intelectual de los judíos de Aviñón y del Condado Venesino constituye un desideratum de la investigación científica al que contribuye este artículo con la publicación de dos poesías litúrgicas inéditas. Una de ellas es un cántico (ms. n° 1774 del Instituto Ben Zvi de Jerusalén) compuesto en 1774 en honor del papa Clemente XIV, Lorenzo Ganganelli, -particularmente favorable a los judíos- que revela la existencia y la obra de un ministro oficiante de Carpentras, Joseph de Meyrargues, autor de esta pieza y de otras composiciones poéticas. Otra de estas composiciones también se publica aquí por vez primera, según el ms. 2610 de la Biblioteca Inguimbertina de Carpentras

The interplay between conformation and absolute configuration in chiral electron dynamics of small diols

A competition between chiral characteristics alternatively attributable to either conformation or to absolute configuration is identified. Circular dichroism associated with photoexcitation of the outer orbital of configurational enantiomers of 1,3- and 2,3-butanediols has been examined with a focus on the large changes in electron chiral asymmetry produced by different molecular conformations. Experimental gas phase measurements offer support for the theoretical modelling of this chiroptical effect. A surprising prediction is that a conformationally produced pseudoenantiomerism in 1,3-butanediol generates a chiral response in the frontier electron dynamics that effectively outweighs the influence of the permanent configurational handedness established at the asymmetrically substituted carbon. Induced conformation, and specifically induced conformational chirality, may thus be a dominating factor in chiral molecular recognition in such systems

Introduction to Social Networking and Communities Minitrack

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La phraséologie du discours médical : Discours pour le grand public ou pour le spécialiste ?

Reposant sur un corpus d'articles médicaux de la presse médicale spécialisée et grand public, notre travail est une étude de la phraséologie du discours médical. La structure du texte et la fonction communicative de chaque partie et segment de texte concourent à l'INFORMATION du lecteur mais lui adressent également un APPEL. L'analyse des unités phraséologiques, métaphoriques ou non, démontre, grâce à la confrontation avec les articles spécialisés, le caractère scientifique de l'article médical grand public