Dynamic coupling of kinetic and continuum solvers for micro gas flow computations

A hybrid method, dynamic coupling the direct numerical solution of the Bhatnagar-Gross-Krook (BGK) kinetic equation and hydrodynamic Navier-Stokes equations is presented. The decomposition of the physical domain into kinetic and hydrodynamic sub-domains is based on the local Knudsen number and macroparameters gradients. The size of these domains will change during the evolution depending on the current value of the criteria. The solution is advanced in time simultaneously in both kinetic and hydrodynamic domains the coupling is achieved by matching half fluxes at the interface of the kinetic and Navier-Stokes domains, thus taking care of the conservation of momentum, energy and mass through the interface. Solver efficiency is increased via MPI (Message Passing Interface) parallelization. The accuracy and properties of the proposed method is assessed via successful computation of the flow through a slit, at pressure ratio of 0.5 and for wide range of Knudsen number

Application of a hybrid kinetic-continuum solver to the near wall modelling

A hybrid method dynamically coupling the direct numerical solution of the S-model kinetic equation and Navier-Stokes equations is applied to a numerical simulation of the flow through the channel of a finite length due to arbitrarily pressure ratios and for a wide range of Knudsen number. The decomposition of the physical domain into kinetic and hydrodynamic sub-domains is updated at each time step. The solution is advanced in time simultaneously in both kinetic and hydrodynamic domains: the coupling is achieved by matching half fluxes at the interface of the kinetic and Navier-Stokes domains, thus taking care of the conservation of momentum, energy and mass through the interface. Solver efficiency is increased via MPI (Message Passing Interface) parallelization. Accuracy and reliability of the method, for different decomposition criteria, are assessed via comparison with a pure kinetic solution

Heat Transfer Correlations for compressible flow in Micro Heat Exchangers

The paper discusses the definition of dimensionless parameters useful to define a local correlation for convective heat transfer in compressible, micro scale gaseous flows. A combination of static and stagnation temperatures is chosen, as it allows to weight the temperature change related to the heat transfer and that induced by conversion of internal energy into kinetic one. The correlation offers a purely convective local Nusselt number, i.e. correlating the heat flow rate with the local flow parameters and wall surface temperature. The correlation is validated through a series of numerical computations in both counter-current and co-current micro heat exchanger configurations. The numerical computations take into account rarefaction and conjugate heat transfer effects

Numerical Modelling of Droplets and Beads Behavior over Super-Hydrophobic and Hydrophilic Coatings under in-Flight Icing Conditions

Featured Application: Use of hydrophobic coatings as passive inflight icing safety device. Current technology has produced a wide range of advanced micro-structured surfaces, designed for achieving the best wettability and adhesion performances for each specific application. In the context of in-flight icing simulations, this opens new challenges since the current most popular and successful ice accretion prediction tools neglect the details of the droplet behavior opting for a continuous film model. Here, a phenomenological model, following, in a Lagrangian approach, the evolution of the single droplets from the impinging to the onset of rivulets, is developed to simulate the performances of super-hydrophobic surfaces in icing application. Possible rebound and droplet spread on the impact, coalescence, single ice bead formation and droplet to rivulet transition are taken into account. The first validation shows how the models are able to predict the anti-icing capability of a super-hydrophobic surface coupled with a heating system

Le Piacevoli e ridicolose simplicitá di Bertoldino. Euskera

Dialecto : texto en euskera occidental -- vizcaíno puristaS. XX -- Periodo : último euskera modernoEuskalkia : mendebalekoa -- bizkaiera garbizaleaXX. md. -- Aroa : azken euskara modernoaTít. de la cub.: Bertolda eta BertoldinDigitalización. Vitoria-Gasteiz : Fundación Sancho el Sabio, 200

Historia de la vida, hechos y astucias sutilísimas del rústico Bertoldo, la de Bertoldino su hijo, y la de Cacaseno su nieto : obra de gran diversión y suma moralidad, donde hallará el sabio muchos que admirar, y el ignorante infinito que aprender

Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-201

Romantismo e objetividade: notas sobre um panorama do Rio de Janeiro

The article deals with the great Panorama of Rio de Janeiro exhibited in Paris, 1824, and its sources - a series of watercolours which have also generated succeeding engravings produced dur-ing the 1830s. Panoramas, in their early formal conventions are shown to interplay with Romanticism's and Naturphilosophie's theses and to put in motion the legacy of 11th-century paint-ing . As this geme of visual device develops, Rio's watercoulours display symptoms of a gradual dismissal of its initial ambilions, through lhe treatment of the natural site and the city. At last the invention of the daguerreotype and vai d'oiseau urban images, among other traits, signale the changes in sensibility related to the production and consumption of those circular canvasses. From 1840/50 on panoramas conceived by the will to fuse art and science and bya reflection on nature and liberty turn essentially into a mass entertainment.Romantismo e objetividade: notas sobre um panorama do Rio de Janeiro Margarelh da Silva Pereira Enfoca O grande Panorama do Rio de Janeiro, exibido em Paris em 1824, do qual se conhece a série de aquarelas que serviram de base tanto àquela ampliação quanto às sucessivas gravuras da cena que foram produzidas na década de 1830. Busca-se mostrar como os panoramas em sua formalização inicial dialogam com as teses do romantismo e da Naturphilosophie, mobilizan-do heranças da pintura seiscentista. No desenvolvimento desta forma de exibição as aquarelas do Rio apresentam sintomas do gradual afastamento das ambições iniciais através do tratamento dispensado ao sítio natural e à cidade. Por fim, a invenção do daguerreótipo, e as vistas urbanas em võo de pássaro, enlre outros, balizariam a mudança de sensibilidade na produção e na fruição dessas telas circulares. A partir de 1840/50 os panoramas engendrados pelo desejo de fusão entre arte e ciência e pela reflexão sobre a natureza e a liberdade, tornar-se-iam, sobretudo, um divertimento de massas

Serum Albumin Is Inversely Associated With Portal Vein Thrombosis in Cirrhosis

We analyzed whether serum albumin is independently associated with portal vein thrombosis (PVT) in liver cirrhosis (LC) and if a biologic plausibility exists. This study was divided into three parts. In part 1 (retrospective analysis), 753 consecutive patients with LC with ultrasound-detected PVT were retrospectively analyzed. In part 2, 112 patients with LC and 56 matched controls were entered in the cross-sectional study. In part 3, 5 patients with cirrhosis were entered in the in vivo study and 4 healthy subjects (HSs) were entered in the in vitro study to explore if albumin may affect platelet activation by modulating oxidative stress. In the 753 patients with LC, the prevalence of PVT was 16.7%; logistic analysis showed that only age (odds ratio [OR], 1.024; P = 0.012) and serum albumin (OR, -0.422; P = 0.0001) significantly predicted patients with PVT. Analyzing the 112 patients with LC and controls, soluble clusters of differentiation (CD)40-ligand (P = 0.0238), soluble Nox2-derived peptide (sNox2-dp; P < 0.0001), and urinary excretion of isoprostanes (P = 0.0078) were higher in patients with LC. In LC, albumin was correlated with sCD4OL (Spearman's rank correlation coefficient [r(s)], -0.33; P < 0.001), sNox2-dp (r(s), -0.57; P < 0.0001), and urinary excretion of isoprostanes (r(s), -0.48; P < 0.0001) levels. The in vivo study showed a progressive decrease in platelet aggregation, sNox2-dp, and urinary 8-iso prostaglandin F2 alpha-III formation 2 hours and 3 days after albumin infusion. Finally, platelet aggregation, sNox2-dp, and isoprostane formation significantly decreased in platelets from HSs incubated with scalar concentrations of albumin. Conclusion: Low serum albumin in LC is associated with PVT, suggesting that albumin could be a modulator of the hemostatic system through interference with mechanisms regulating platelet activation