14th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
The aim of this work is to study the influence of different sub-grid scale (SGS) closure models and inflow turbulence conditions on the boundary layer transition on a suction side of a highly loaded transonic turbine cascade in presence of free-stream turbulence using Large Eddy Symulations (LES). For the numerical simulations the MUR237 flow case was considered and the incoming free-stream turbulence was reproduced using the Synthetic Eddy Method (SEM) of Jarrin. The boundary layer transition on the blade suction side was found to be significantly influenced by the choice of the SGS closure model and the SEM parameters. These two aspects are carefully evaluated in this framework. Initially, the influence of three different closure models (Smagorinsky, WALE and TKE) was evaluated. Among them the WALE SGS closure model performed best compared to the Smagorinsky and TKE models and for this reason was used in the following analysis, where different values of turbulent length scales, eddies density and inlet turbulence for the SEM were evaluated. As it is shown in the results, among the different parameters the choice of the turbulent length scales plays a major role on the transition onset on the blade suction side.