VORTEX - Grupo de Mecânica dos Fluidos de Escoamentos Complexos


Um modelo k - w para escoamentos turbulentos parietais dilatáveis (2006)

Autor: Daniel Vieira Soares

Orientador: José Luiz Alves da Fontoura Rodrigues

Resumo
The main goal of this work is to extend the K − W turbulence model proposed by Bredberg (2002), originally developed in order to simulate turbulent isothermal flows in which adverse pressure gradients occur, to simulate the effects of density variations exclusively due to the presence of thermal gradients - cases vastly applied in industry - implementing in a new version of the academic code TURBO-2D, with sequential semi-implicit time resolution and spatial discretization via P1/IsoP2 finite elements. The development of the K − W model extension is based in the work of Munhoz da Cruz (1989), to numerically solve thermal flows including extra terms in the turbulence quantities equations, derived from the influence of density variations on the fluid motion. Such study is rarely treated by low-Reynolds RANS turbulence models. Four test cases were selected to validate the model implementation, due to the good results available in the literature: two isothermal cases with boundary-layer separation, the divergent channel of Driver and Seegmiller (1985) and the steep hill of Loureiro et. al (2005), and two thermal boundary-layer cases, the forced convection over a strongly heated wall of Ng (1981), and the natural convection boundary layer of Tsuji and Nagano (1988), which makes possible to perform a deeper analysis of the density variation influence over the turbulent flow characteristics. The simulations results were compared to other simulations with the K − E turbulence model implemented in the code TURBO-2D, extensively tested and validated by Soares and Fontoura Rodrigues (2004) and (2005), using the classic log-law for velocity, the temperature log-law of Cheng and Ng (1982), the velocity laws of the wall of Mellor (1966) and of Nakayama and Koyama (1984), and the velocity and temperature laws of the wall of Cruz and Silva Freire (1998 and 2002, respectively), and compared to the experimental data and results from other simulations, available in the literature.

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