In modern gas turbine blades it has been a common practice to use cooling passages in gas turbine blades. In cooling processes blades have excessive thermal stresses, causing creep, oxidizing and also melting in some cases. Therefore fully understanding of the flow characteristics in the U-bend is important in designing cooling passages. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, and to improve the cooling performance, both refined turbulence models and higher-order numerical schemes are indispensable tools for turbine designers. It is the conventional belief and practice that the usage of a proper turbulence model and a reliable numerical method achieves accurate computations. The three-dimensional turbulent flows and heat transfer in a square U-bend duct are numerically studied by using a Large Eddy Simulation (LES) model. Simulation using k-ω, k-ε and RSM models has been previously reported, and used here to compare with the LES simulation. The finite volume method incorporated with higher-order bounded interpolation scheme has been employed in the present study. The objective of this study is to validate the simulation of LES model with the experimental results. Three different Reynolds numbers, 36000, 60000 and 100000, were used. This study concludes that the RSM is a better model, for Re = 36,000 and 60,000.

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