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

This is Part II of a companion article which introduced the implementation of a wall-modeled large-eddy simulation (WMLES) model combined with the immersed boundary method 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 the current WMLES, showing the latter with a superior ability to capture transitional behaviors of the boundary layers, turbulent kinetic energy production/convection and dissipation. Such initial stages of the analysis pave the way for characterizing the vane's momentum and thermal losses. Consequently, the local heat transfer characteristics of the cascade are analyzed using a dedicated coefficient designed to quantify the thermal exchange. 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.