Wall-Modeled LES of a Transonic Gas Turbine Vane - Part II: Mach Number Effect and Losses Prediction

Abstract This is part II of a companion paper which introduced the implementation of a Wall-Modeled Large-Eddy Simulation (WMLES) model combined with the Immersed Boundary Method (IBM) to analyze transonic flow in a gas turbine nozzle guide vane. In particular, Part I focused on a fully transonic configuration, validating the model against experimental data, identifying the most cost-effective model in terms of accuracy and computational effort, and demonstrating the benefits of scale-resolved approaches by characterizing the primary scales of wake motion. Part II expands on this by investigating the effects of flow compressibility and comparing high subsonic and fully transonic cases within the same environment. In particular, after initial verification of the numerical model robustness, the instantaneous, near-wall, and averaged flow dynamics are investigated as a function of the cascade expansion ratio. Steady Reynolds-Averaged Navier-Stokes solutions are also compared with current WMLES, showing the latter with a superior ability to capture transitional behaviors of the boundary layers, turbulent kinetic energy production/convection and dissipation, and predicting a more consistent behavior of wall thermal properties. Such initial stages of the analysis pave the way for characterizing the vane's momentum and thermal losses. Consequently, a novel thermal loss coefficient is proposed, accounting for the localized cooling effects. Finally, Lagrangian statistics within the scale-resolved framework are presented, underscoring the role of compressibility in the wake turbulent behavior and primary frequencies of the system.