On stability and turbulence of fluid flows

This investigation is divided into two parts, the treatment of the stability problem of fluid flows on the one hand, and that of the turbulent motion on the other. The first part summarizes all previous investigations under a unified point of view, that is, sets up as generally as possible the conditions under which a profile possesses unstable or stable characteristics, and indicates the methods for solution of the stability equation for any arbitrary velocity profile and for calculation of the critical Reynolds number for unstable profiles. In the second part, under certain greatly idealizing assumptions, differential equations for the turbulent motions are derived and from them qualitative information about several properties of the turbulent velocity distribution is obtained

Elementos de contorno de Galerkin simétrico

Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2019.Este trabalho apresenta uma abordagem detalhada para a formulação do método dos elementos de contorno simétrico de Galerkin para problemas bidimensionais. Sua validação foi realizada a partir da implementação numérica de um programa em linguagem MatLabr aplicado a problemas de condução de calor e comparado a programas de elementos de contorno por colocação reconhecidos pela literatura. A validade do código de Galerkin simétrico pôde ser confirmada. Como a formulação bidimensional pode ser estendida a certo ponto para o caso tridimensional, foi efetuado o estudo da biblioteca de código aberto Bempp devido a utilidade do programa para solucionar problemas tridimensionais de engenharia utilizando o método dos elementos de contorno de Galerkin simétrico. A verificação de sua eficácia foi explorada a partir de sua aplicação em um problema térmico onde foi observada sua atratividade para o meio universário devido a suficiência para resolver problemas relativamente pequenos. No entanto, apresentou performance abaixo do esperado em problemas grandes e complexos.This thesis presents a detailed approach to the formulation of symmetric Galerkin boundary element method for two-dimensional problems. A validation was performed using the numerical implementation in MatLabr language, which was applied to heat conduction problems and compared to collocation boundary element programs legitimized by the literature. The validity of the symmetric Galerkin code is confirmed. Since the two-dimensional formulation can be extended to a certain extent for the three-dimensional case, the Bempp open source library was studied because of the utility of the software to solve three-dimensional engineering problems using the Galerkin boundary element method. The verification of its effectiveness was explored from its application in a thermal problem, where it was observed its attractiveness to the university environment due to an efficiency to solve relatively small problems, however, presented underperformance in large and complex problems