On- and Off-Design Endwall Aerodynamics of a High-Speed Low-Pressure Turbine Linear Cascade: Sensitivity to the Inlet Turbulence Profile

In current low-pressure turbine cascades, around a third of the losses are determined by the complex interaction between endwall boundary layers and blade profiles. Research has focused on the origin of secondary flow structures through numerical and experimental approaches, which shed light on vorticity transport throughout the cascades. This paper details the study of the endwall flow characteristics in the newly published open-access high-speed low-pressure turbine cascade SPLEEN. This study focuses on the effect of inlet turbulence profile specification, which is studied by computational fluid dynamics in design and off-design conditions. Numerical simulations are performed using transition-sensitive Reynolds-Averaged Navier-Stokes closures, which have proved to be a reliable tool for identifying secondary flow structures in similar configurations. In this activity, RANS-based transition models capture the secondary flow structure, but underestimate mixing and over-predict losses near the hub. Inlet turbulence profiles have little effect on endwall pressure, while higher turbulence intensity and integral length scales enhance secondary flow mixing, reduce vortex penetration, and increase hub losses. In off-design conditions, a low Mach number increases secondary flow penetration and endwall losses, whereas a high Reynolds number reduces both profile and endwall losses. Finally, selected correlations from the literature agree at the nominal Reynolds number but do not capture the variations across the various conditions explored.