Analysis of a Realizable Unified RANS-LES Model

Large Eddy Simulation (LES) is computationally expensive at high Reynolds numbers (Re), especially for the accurate resolution of the near-wall region in wall-bounded flows. Hence, hybrid turbulence models have been developed to reduce the computational cost of LES. In the hybrid modeling approach, the nearwall region is modeled using Reynolds-averaged Navier-Stokes (RANS) methods while regions away from the wall are modeled using LES. However, the recently proposed hybrid turbulence models cannot be seen as real unified turbulence models. Hence, there is a need for the development of unified turbulence models which can be used continuously as LES or RANS methods. The formulation of a realizable unified turbulence model and the evaluation of its properties will be addressed in the current study. Turbulent channel flow is used as the test case to evaluate the unified turbulence model. The accuracy of the numerical predictions are validated against a benchmark DNS data. It was found that the numerical simulations of the unified turbulence model are more accurate than LES on coarse grids. Also, the numerical predictions of the unified turbulence model was less sensitive to the choice of the RANS model in the near-wall region. The current study provides encouraging results for the use of the unified turbulence model considered to investigate complex turbulent flows.