A blessed endoscopy

info:eu-repo/semantics/publishedVersio

Lattice-Boltzmann Method for Non-Newtonian Fluid Flows

We study an ad hoc extension of the Lattice-Boltzmann method that allows the simulation of non-Newtonian fluids described by generalized Newtonian models. We extensively test the accuracy of the method for the case of shear-thinning and shear-thickening truncated power-law fluids in the parallel plate geometry, and show that the relative error compared to analytical solutions decays approximately linear with the lattice resolution. Finally, we also tested the method in the reentrant-flow geometry, in which the shear-rate is no-longer a scalar and the presence of two singular points requires high accuracy in order to obtain satisfactory resolution in the local stress near these points. In this geometry, we also found excellent agreement with the solutions obtained by standard finite-element methods, and the agreement improves with higher lattice resolution

Spin-orbit mode transfer via a classical analog of quantum teleportation

We translate the quantum teleportation protocol into a sequence of coherent operations involving three degrees of freedom of a classical laser beam. The protocol, which we demonstrate experimentally, transfers the polarisation state of the input beam to the transverse mode of the output beam. The role of quantum entanglement is played by a non-separable mode describing the path and transverse degrees of freedom. Our protocol illustrates the possibility of new optical applications based on this intriguing classical analogue of quantum entanglement.Comment: 5 pages, 7 figure

The scenario of two-dimensional instabilities of the cylinder wake under EHD forcing: A linear stability analysis

We propose to study the stability properties of an air flow wake forced by a dielectric barrier discharge (DBD) actuator, which is a type of electrohydrodynamic (EHD) actuator. These actuators add momentum to the flow around a cylinder in regions close to the wall and, in our case, are symmetrically disposed near the boundary layer separation point. Since the forcing frequencies, typical of DBD, are much higher than the natural shedding frequency of the flow, we will be considering the forcing actuation as stationary. In the first part, the flow around a circular cylinder modified by EHD actuators will be experimentally studied by means of particle image velocimetry (PIV). In the second part, the EHD actuators have been numerically implemented as a boundary condition on the cylinder surface. Using this boundary condition, the computationally obtained base flow is then compared with the experimental one in order to relate the control parameters from both methodologies. After validating the obtained agreement, we study the Hopf bifurcation that appears once the flow starts the vortex shedding through experimental and computational approaches. For the base flow derived from experimentally obtained snapshots, we monitor the evolution of the velocity amplitude oscillations. As to the computationally obtained base flow, its stability is analyzed by solving a global eigenvalue problem obtained from the linearized Navier–Stokes equations. Finally, the critical parameters obtained from both approaches are compared

Simulation of the velocity field in compound channel flow using different closure models

1st European IAHR Congress,6-4 May, Edinburg, ScotlandIn this study a comparison of three turbulence closure models (two isotropic and one anisotropic) with experimental data is performed. The interaction between the main channel (MC) flow and the floodplain (FP) generates a complex flow structure. A shallow mixing layer develops between the MC flow and the slower FP flow generating a high horizontal shear layer, streamwise and vertical vortices, momentum transfer and other phenomena, related to velocity retardation and acceleration. This phenomenon dissipates part of the kinetic energy and contributes to the reduction of the velocity differences between the MC and the FP. The large scale vortices that are generated in the shear layer are anisotropic, provoking the formation of secondary flow cells that influence the primary velocity distribution. These threedimensional turbulent structures can be reasonable well reproduced by a simple anisotropic model (Algebraic Stress Model). The isotropic models are capable of simulating the boundary layer, especially the model base in k-ω equations, but cannot simulate the shear layer that develops at the interface

Verification and validation of computational fluid dynamics simulations of compound channel

In this study the verification and validation of a 2nd order turbulence closure model is performed for an experimental compound channel flow, where the velocity field was measured by a Laser Doppler Velocimeter. Detailed Explicit Algebraic Reynolds Stress Model (EARSM) simulation is reported. The Grid Convergence Index (GCI) approach proposed by Roache (1998) was adopted to evaluate the uncertainty associated to grid resolution. The velocity components, the turbulent kinetic energy (TKE) and the dissipation rate were used as variables of interest. The GCI results present low values for the streamwise velocity, TKE and dissipation rate, but higher values in what concerns vertical and spanwise velocities. This indicates that the mean primary flow has converged but the secondary flow field still depends on grid resolution. Based on GCI values distribution, the mesh was locally refined. Comparison of numerical and experimental results shows good agreemen

A relação sujeito-objeto em Paul Tillich: A estrutura do conhecimento e a perspectiva teológica

The article presents the relation subject-object in the Paul Tillich’s understanding as an original structural conception, a relation based on the structure "I-world". The Lebenswelt is the original and fundamental form of the relation subject-object. This ontology basis permits fundamentals interpretative elements to a reaffirmation of the concepts "subjective" and "objective", those concepts can be denied in some spheres of knowledge such as depriving its appropriation (bedingt) from its subjective or denying the affirmation of its objective. This article intends to show that Paul Tillich understands that Theology cannot deal with the concept "God" like a mere object of knowledge, avoiding the perilous attitude of religious objectification. The conclusion intends to understand the non-derivative character of this structure subject-object, the impossibility of understanding what precede this duality, only comprehensive by the revelation.O artigo apresenta a relação sujeito-objeto no pensamento de Paul Tillich como uma concepção estrutural originária, isto é, uma relação baseada na estrutura "eu-mundo". O Lebenswelt é a forma originária e fundante da relação sujeito-objeto. Esta base ontológica propiciará elementos interpretativos fundamentais para uma reafirmação dos conceitos de "subjetividade" e "objetividade", os quais podem ser negados em certas esferas práticas do conhecimento tanto como forma de apropriação do saber sobre as coisas privando-as (bedingt) de sua subjetividade, quanto negando a afirmação de sua objetividade. Pretende-se, a partir de então, demonstrar que a teologia não pode submeter o conceito de "Deus" a mero objeto do conhecimento, devendo evitar assim o perigo da objetivação religiosa. A conclusão do ensaio preocupar-se-á em entender o caráter não-derivativo desta estrutura básica sujeito-objeto, isto é, a impossibilidade de compreender o que precede esta dualidade a não ser através da revelação

Verification and validation of computational fluid dynamics simulations of compound channel

In this study the verification and validation of a 2nd order turbulence closure model is performed for an experimental compound channel flow, where the velocity field was measured by a Laser Doppler Velocimeter. Detailed Explicit Algebraic Reynolds Stress Model (EARSM) simulation is reported. The Grid Convergence Index (GCI) approach proposed by Roache (1998) was adopted to evaluate the uncertainty associated to grid resolution. The velocity components, the turbulent kinetic energy (TKE) and the dissipation rate were used as variables of interest. The GCI results present low values for the streamwise velocity, TKE and dissipation rate, but higher values in what concerns vertical and spanwise velocities. This indicates that the mean primary flow has converged but the secondary flow field still depends on grid resolution. Based on GCI values distribution, the mesh was locally refined. Comparison of numerical and experimental results shows good agreemen