A Hybrid RANS-LES Modeling Methodology Sensitized to Transitional and Curvature/Rotation Effects

Abstract

This paper presents a new hybrid model that seeks to combine the strengths of Reynolds–averaged Navier-Stokes (RANS) and large eddy simulation (LES) methods. The new model is based on a recently proposed version of a dynamic hybrid RANS-LES (DHRL) framework that addresses several deficiencies inherent in most current hybrid models, including explicit grid dependence, boundary layer model stress depletion, and delayed shear layer breakdown. The DHRL framework is highly generalized, allowing coupling of any desired LES model with any given RANS model. In this study, a recently proposed four-equation eddy-viscosity model (EVM) capable of predicting both flow transition from laminar-to-turbulent (T) and rotation and/or streamline curvature (RC) effects is used for the RANS component, and a monotonically-integrated LES (MILES) scheme is used for the LES component. The new model (DHRL with T-RC effects) is implemented into a commercial computational fluid dynamics (CFD) code and investigated against three different flow configurations. The test cases include nonrotating and rotating channel flow, zero-pressure-gradient (ZPG) boundary layer flow over a flat plate, and flow over a circular cylinder. Results obtained from the numerical simulations indicate that the new hybrid model produces significant levels of turbulent fluctuations in the flowfield and successfully resolves T-RC effects. The results show improved accuracy compared to RANS models and are obtained at a significant reduction of computational cost compared to full LES models. Further investigation on complex test cases is warranted before commenting on the accuracy and potential usage of the model as a practical tool.