Numerical analysis of the turbulent coaxial jets / Análise numérica de jatos coaxiais turbulentos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The understanding of the jets behavior is of extreme importance in several practical applications in combustion and propulsion. Therefore, it becomes more and more important the detailed analysis of the parameters that affect the characteristics of this type of flow. This work presents a numerical study of the incompressible turbulent coaxial jets characteristics, based in the analysis of the variation in the velocities ratio of the internal and external jets, and of the variation in the nozzles internal to external diameter relation. The turbulent jets characteristics analyzed in this work are the decay of the centerline speed, the spreading rate, the length of the potential cores, the mean velocity profiles, the Reynolds stress distribution, the variation of turbulent viscosity, the turbulent kinetic energy and the dissipation rate of turbulent kinetic energy. The Reynolds decomposition process, generally applied to incompressible and compressible flows, were used as mathematical tool in the formulation of the turbulent flow. This decomposition process supply the Reynolds Averaged Navier-Stokes equation. For the closing of the mean equations becomes necessary the modeling of the unknown terms (Reynolds stress) that arise due the non linearity of the instantaneous equations in the mean flow. Therefore, it is necessary to use turbulence models to model the Reynolds stress. The numerical solution of the equations were carried through the use of a developed application to solve specific problems in continuous mechanics. This application, called OpenrFOAM, are a C++ library, of open source code for Computational Fluid Dynamics, that uses a finite volume method in the equation discretization. Besides the analysis of turbulent coaxial jets, the numerical analysis of a coaxial jets configuration identical of the axisymmetrical simple jet has also been carried. And also of coaxial jets configuration with a nozzles areas ratio similar of a Delft piloted jet diffusion flame burner, considering simple coaxial nozzles without edge between the two jets and also the influence of the edge between the burner nozzles. As results, it was possible to get results that had been compared with others authors in similar configurations and other results not available in the literature, observing the main differences between them.

ASSUNTO(S)

engenharia e tecnologia espacial turbulência combustÃo e propulsÃo coaxial jets jato simples simple jet método de volumes finitos turbulence jatos coaxiais finite volume meterod dinâmica dos fluidos computacionais combustion and propulsion computational fluid dynamics space engineeging and technology

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