Jorge Rodolfo Silva Zabadal

Solution of the three-dimensional one-group discrete ordinates problems by the LTSn method

Abstract In this work, the LTS n formulation is extended to the three-dimensional discrete ordinates problems in cartesian geometry. Numerical simulations are presented for problems with cylindrical geometry.

General solution of one-dimensional approximations to the transport equation

Abstract The aim of this work is to present a complete review of the generic method for solving analytically one-dimensional approximations of the transport equation that appear as a set of first order linear differential equations, employing the Laplace transfrom technique over a finite domain. Recent advances are also included.

An analytical solution for the two-dimensional discrete ordinates problem in a convex domain

The aim of this work consists in the application of the Laplace transform technique to solve analytically the transverse integrated discrete ordinates equations in curvilinear orthogonal coordinates system for a convex domain.

Solutions to the multidimensional linear transport equation by the spectral method

The spectral method is used to develop a solution for multidimensional transport problems for neutral particles in cartesian geometry. The procedure is based on the expansion of the angular flux in a truncated series of orthogonal polynomials that results in the transformation of the multidimensional problem into a set of one-dimensional problems, whose solutions are well established. The convergence of this approach is studied in the context of the multidimensional discrete-ordinates equations.

Improved Dancoff factors for cluster fuel bundles by the WIMSD code

Abstract The recently developed tracking routine PIJM, for computing improved two-dimensional first-flight collision matrices for the WIMSD code, has been modified to evaluate black Dancoff factors for cluster fuel bundles in unit cells with cylindrical outer boundaries. The routine, similar to the original PIJ but employing an efficient in-plane integration scheme of the Bickley functions appearing in those expressions, is first compared with the accurate Carlvik method in the calculation of Dancoff factors for regular lattices, both with and without a gap surrounding the fuel rods. Dancoff factors for the more general cases of CANDU37 and CANFLEX fuel bundles are next obtained and compared with Monte Carlo based calculations, illustrating the accuracy of the proposed scheme.

Determination of a closed-form solution for the multidimensional transport equation using a fractional derivative

Abstract In this work we construct a closed-form solution for the multidimensional transport equation rewriten in integral form which is expressed in terms of a fractional derivative of the angular flux. We determine the unknown order of the fractional derivative comparing the kernel of the integral equation with the one of the Riemann–Liouville definition of fractional derivative. We report numerical simulations.

On a New Definition of the Reynolds Number from the Interplay of Macroscopic and Microscopic Phenomenology

Turbulence is a behavior seen in many fluid flows, which is conjectured to be driven by the inertia to viscosity force ratio, i.e. the Reynolds number. Even though research in turbulence has existed for more than a century there is still no consensus as how to elaborate a self-consistent and genuine theory, which describes the dynamics of a transition from a laminar to a turbulent regime or vice versa, and the geometric flow structure of turbulent phenomena. So far, it is believed that the Navier–Stokes equations model turbulence in an adequate way. However the existence of general solutions in three plus one space–time dimensions is still an open question (Cao, Titi 2007), (Cao, Titi 2008), (Constantin 2001), (Constantin et al. 2007), (Fefferman 2006).

Solution of the multilayer multigroup neutron diffusion equation in cartesian geometry by fictitious borders power method

Abstract In this paper a solution for the one-dimensional steady state Multilayer Multigroup Neutron Diffusion Equation in cartesian geometry by Fictitious Borders Power Method and a perturbative analysis of this solution is presented. For each new iteration of the power method, the neutron flux is reconstructed by polynomial interpolation, so that it always remains in a standard form. However when the domain is long, an almost singular matrix arises in the interpolation process. To eliminate this singularity the domain segmented in R regions, called fictitious regions. The last step is to solve the neutron diffusion equation for each fictitious region in analytical form locally. The results are compared with results present in the literature. In order to analyze the sensitivity of the solution, a perturbation in the nuclear parameters is inserted to determine how a perturbation interferes in numerical results of the solution.

Tanque Hidráulico Experimental para cálculo de perda de carga em tubulações

O artigo descreve a construcao de um tanque hidraulico para o calculo da perda de carga em dutos cilindricos retos e a execucao dos ensaios. O tanque possui estrutura simples, baixo custo, robustez e versatilidade necessarias para a realizacao de ensaios de facil execucao, baseados no registro dos tempos associados a variacao da altura da coluna de agua num tubo vertical. A utilizacao deste equipamento em aulas experimentais mostrou-se muito eficaz, possibilitando a comprovacao de resultados teoricos a partir da utilizacao de modelos reais. Os resultados obtidos sao apresentados em planilhas eletronicas, cuja elaboracao baseou-se na aplicacao dos principios de conservacao de massa e energia no escoamento de fluidos viscosos, e nas equacoes de perda de carga distribuida e localizada. O experimento proposto constitui uma ferramenta pedagogica interessante, tendo em vista que sua execucao requer a participacao ativa dos alunos na realizacao dos ensaios e na execucao de calculos. A rotina de calculos, visando comparar valores experimentais perda de carga obtidos experimentalmente com valores teoricos, abrange uma serie de conceitos e equacoes da Mecânica dos Fluidos, propiciando que a aprendizagem desse conteudo seja feita a partir de um problema real.

Impactos Computacionais de uma Implementação de Criptografia Visual

Este artigo realiza breve estudo sobre a Criptografia Visual, vindo a implementar um prototipo para fins de identificar caracteristicas de processamento quando do emprego dessa tecnologia. Foi avaliado o impacto de recursos computacionais quando do uso do prototipo. Destaca-se ja haver aplicacoes reais em mercado, o que pode oportunizar situacoes interessantes de investigacao. Para o desenvolvimento do prototipo, considerando-se o seu emprego para fins didaticos, implementou-se em Object Pascal – no caso, Delphi, mas poder-se-ia empregar Lazarus ou Kylix - e, para fins de configuracoes do tratamento grafico, a linguagem Lua. Medicoes de desempenho nao se revelaram elevadas.