IMPROVEMENT OF STANDARD K-EPSILON TURBULENCE MODEL FOR ROUND FREE JETS BY ADJUSTING CLOSURE COEFFICIENTS

In this study, round free jet was modeled with standard k-ε turbulence model and the results were compared with the measurements. The aim of the study is to improve the prediction capability of standard k-ε turbulence model, that is not very successful in modeling flows with anisotropic Reynolds stress tensors such as jet flows. It was aimed to investigate the effect of model constants such as C_ε1, the coefficient of turbulent production; C_ε2, the coefficient of turbulent kinetic energy dissipation and C_μ, used to calculate turbulence viscosity. Steady-state and three-dimensional CFD analyses have been performed for these constants and the results were evaluated based on dimensionless velocity and turbulence profiles, jet half-thicknesses, centerline velocity and turbulence intensity (TI) on the jet axis. It was observed that the adjusted new constants achieve more successful results than the default coefficients. By calibrating the model coefficients that differ from the default model coefficients by 16% for C_ε1, 17% for C_ε2, and 1.2% for C_μ, it is revealed that jet centerline velocity distribution and jet half-width distribution along the jet axis can be estimated better. The new closure coefficients were also validated for Reynolds numbers of 5000 and 20000. The CFD simulations revealed that the velocity-profile change with the adjusted model coefficients and the numerical results agreed well with the experimental data. By this way, the calculation errors due to uncertainty of turbulence modeling encountered in some CFD calculations is reduced.