Wall-Modeled Large-Eddy Simulation of a Transonic Gas Turbine Vane - Part I: Model Setup and Assessment of Turbulent Length Scales

The implementation of a wall-modeled large eddy simulation (WMLES) model combined with an immersed boundary method (IBM) to investigate the detailed aerodynamics of a gas turbine stator operating in a transonic regime is introduced in this study. In Part I, the potential of scale-resolved simulations within the WMLES framework is exploited by analyzing length scales and coherent structures within the wake. After a validation of the numerical model against experimental data and the identification of the optimal computational grid for balancing cost and accuracy, the presence of coherent vortices within the wake is underscored by the findings, characterized by sizes approximately 0.05 times the chord length and exhibiting primarily isotropic behavior in the cascade plane. Moreover, analysis of velocity fluctuations' probability density functions reveals that the turbulence released is predominantly two-dimensional. Concurrently, examination of pressure signals shows the persistence of a stabilization frequency well beyond the trailing edges of the cascade contrasting with the shedding frequency. Finally, it is demonstrated that as the flow traverses the cascade, its average turbulent content escalates by roughly three orders of magnitude compared to the inflow turbulence levels.