A Transition-Sensitive Hybrid RANS/LES Modeling Methodology for CFD Applications

Alam, M. F., Walters, K., & Thompson, D. (2013). A Transition-Sensitive Hybrid RANS/LES Modeling Methodology for CFD Applications. AIAA 51st Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition. Grapevine, TX.

Abstract

In recent years, the use of Hybrid RANS/LES (HRL) models has become more common in CFD simulations, since HRL models include characteristics of both RANS and LES models to offer more accuracy than RANS in regions of flow separation at a reduced cost relative to LES in attached boundary layers. Although HRL models are widely used in turbulent flow simulations, they have limitations for transitional flow predictions. Most of the HRL models include a fully turbulent RANS model component for boundary layer regions. The small number of HRL models that include transition-sensitive RANS models have issues related to the RANS model itself and to the zonal transition between RANS and LES. In order to address those issues, a new transition-sensitive HRL modeling methodology has been developed that includes a dynamic HRL (DHRL) methodology and a physics-based transition-sensitive RANS model. The feasibility of the transition-sensitive dynamic HRL (TDHRL) model has been investigated by performing numerical simulations of the flow over a PAK-B airfoil at different Reynolds numbers and FSTI conditions. Transient simulations using the Delayed Detached Eddy Simulation (DDES) model and the TDHRL model are performed at Re = 25,000 and Re = 100,000 for low FSTI and Re = 100,000 for high FSTI conditions. Comparison with experimental measurements and DDES model computational results illustrates the potential of TDHRL model for accurately capturing the physics of complex transitional flow phenomena.