Abstract
Most of the RANS turbulence models solve the Reynolds stress by linear hypothesis with isotropic model. They can not capture all kinds of vortexes in the turbomachineries. In this paper, an improved nonlineark-εturbulence model is proposed, which is modified from the RNGk-εturbulence model and Wilcox'sk-ωturbulence model. The Reynolds stresses are solved by nonlinear methods. The nonlineark-εturbulence model can calculate the near wall region without the use of wall functions. The improved nonlineark-εturbulence model is used to simulate the flow field in a curved rectangular duct. The results based on the improved nonlineark-εturbulence model agree well with the experimental results. The calculation results prove that the nonlineark-εturbulence model is available for high pressure gradient flows and large curvature flows, and it can be used to capture complex vortexes in a turbomachinery.
Highlights
Boussinesq hypothesis is a first-order-closure model of turbulence which assumes an explicit algebraic relationship between Reynolds stresses and mean-velocity gradients
The nonlinear k-ε turbulence model was used to simulate the flow in a curved rectangular duct, and the results of the internal flow were compared with experimental data
To prove that the nonlinear k-ε turbulence model is available for capturing complex flow, a three-dimensional (3-D) curved rectangular duct was studied and the results of the internal flow were compared with experimental data
Summary
Boussinesq hypothesis is a first-order-closure model of turbulence which assumes an explicit algebraic relationship between Reynolds stresses and mean-velocity gradients. The Boussinesq hypothesis is a popular linear eddy-viscosity model, which is used in most Reynolds averaged NaviesStocks equations to predict the sheer stress. One way to model the anisotropy is to use the Reynolds stress transport equations. Lubcke et al [6] used another way to simulate the anisotropy They presented an explicit Reynolds-stress closure which offers a physically sound extension of the most prominent linear Boussinesq viscosity models with modest computational effort. Model differs from the family of conventional nonlinear eddy-viscosity models In this approach, elliptic wall effects are accounted for indirectly through the solution of modified Helmholtz equation [11,12,13]. The nonlinear k-ε turbulence model was used to simulate the flow in a curved rectangular duct, and the results of the internal flow were compared with experimental data
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