Singularities at rims in three-dimensional fluid flow

Asymptotic solutions are presented for Stokes flow near circular rims in three-dimensional geometries. Using nonstandard toroidal coordinates, asymptotic analytical expressions are derived for different corner angles. In comparison to the two-dimensional case, an extra critical corner angle value is derived, below which the swirling behaviour of a particle is absent. Illustrations of the motion of a particle near a rim in a three-dimensional fluid flow are given for different corner angles

Axion Electrodynamics from Infeld-van der Waerden formalisms

In this article we will explore the spacetime phase structure inside the Infeld-van der Waerden formalisms, showing that Maxwell's theory in this scenario leads to an axion-like phase electrodynamics, which suggests that this phase may originate the axion field.Comment: 15 page

Comparison of dns of compressible and incompressible turbulent droplet-laden heated channel flow with phase transition

In this paper a turbulent channel flow with dispersed droplets is examined. The dispersed phase is allowed to have phase transition, which leads to heat and mass transfer between the phases, and correspondingly modulates turbulent flow properties. As a point of reference we examine the flow of water droplets in air, containing also the vapor of water. The key element of this study concerns the treatment of the carrier phase as either a compressible or an incompressible fluid. We compare simulation results obtained with a pseudo-spectral discretization for the incompressible flow to those obtained with a finite volume approach for the compressible flow. The compressible formulation is not tailored for low Mach flow and we need to resort to a Mach number that is artificially high for simulation feasibility. We discuss differences in fluid flow, heat- and mass transfer and dispersed droplet properties. The main conclusion is that both formulations give a good general correspondence. Flow properties such as velocity fields agree very closely, while heat transfer as characterized by the Nusselt number differs by around 25%. Droplet sizes are shown to be slightly larger, particularly in the center of the channel, in case the compressible formulation is chosen. A low-Mach compressible formulation is required for a fully quantitative comparison

Mass transport in a partially covered fluid-filled cavity

A method of computing the concentration field of dissolved material inside an etch-hole is presented. Using a number of assumptions, approximate convection-diffusion equations are formulated, and analytical descriptions for the concentration in different parts of the domain are obtained. By coupling these descriptions the concentration field can be computed. The assumptions and the results are validated by comparison with solutions based on a finite-volume method. Results of the boundary-layer method are given for two characteristic etch-hole geometries. The described boundary-layer method is efficient in terms of computational time and memory, because it does not require the construction of a computational grid in the interior of the domain. This advantage will be exploited in a future paper where the method will be used to simulate wet-chemical etching

Comparação entre franquia e negócio independente face ao risco do negócio

TCC (Graduação) - Universidade Federal de Santa Catarina. Centro Socioeconômico. Curso de Ciências ContábeisEste trabalho foi desenvolvido com o objetivo de comparar franquias e negócio independente face ao risco do negócio de cada uma dessas modalidades. Definido o tema central da pesquisa, fez-se um levantamento bibliográfico acerca do sistema de franchising e negócio independente. As características dessa pesquisa são: a) exploratória, por ter como finalidade desenvolver e esclarecer conceitos e idéias para formulação de estudos posteriores; b) descritiva, por procurar descrever a realidade sem modificá-la; c) abordagem qualitativa, por ter um ambiente natural como fonte direta de dados e o pesquisador como instrumento fundamental para análise do exposto. Ter um empreendimento próprio é o anseio de muitas pessoas e grande parte delas costuma ter dúvidas a respeito de qual negócio estabelecer. O sistema franquias é uma alternativa. É um sistema que concede sua marca e nome para outrem comercializar seus produtos e/ou serviços. Muitas são as diferenças entre o franchising e o negócio independente. A partir da comparação das vantagens e desvantagens de cada um desses empreendimentos, pode-se concluir que a escolha entre o negócio independente ou do sistema de franquias depende muito do perfil do empreendedor, face aos riscos que irá enfrentar