| Summary: | 碩士 === 中華大學 === 機械與航太工程研究所 === 94 === In this research, turbulence models were divided into three categories. The first category uses wall distance in their damping function, such as κ-ε turbulence models of Chien and Nagano & Kim. The second category couples the wall distance with turbulence kinetic energy in their damping function, such as κ-ε turbulence models of Fan, and Yang & Shih. The last category is a wall-distance-free turbulence model. They are Wilcox’s κ-ω turbulence model, Jones & Launder κ-ε turbulence model、Launder & Sharma κ-ε turbulence model and Goldberg & Apsley κ-ε turbulence model. A fully developed turbulence pipe flow was used to examine the performance of these turbulence models. The results showed the κ-ε turbulence models of Chien and Fan, and κ-ω turbulence model of low Reynolds number perform better in terms of velocity distribution, turbulence kinetic energy distribution, and dissipative rate distribution. Two reversed flow problems were used to validate these turbulence models. The first case is the channel flow over a two-dimensional hump. The second problem is the flow over a slanted backward-facing step. In both cases, the Chien’s κ-ε turbulence model gives the best velocity distribution and eddy viscosity distribution among these three models. The κ-ε turbulence model of fan gives almost the same result of Chien’s. The low Reynolds number κ-ω turbulence model provides a much smaller eddy viscosity and lack of mixing in the region of reverse flows. The difference between the current turbulence calculation and experiment is still large. Further modification of the turbulence models is still required.
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