Non-ideal fluid turbulent boundary layers in supercritical carbon dioxide compressor cascades: A high-fidelity simulation study near the critical point

This paper presents one of the first high-fidelity numerical investigations of supercritical carbon dioxide (sCO2) turbulent boundary layers in a compressor cascade, conducted without turbulence modeling to ensure physical consistency and capture the intrinsic flow physics near the critical point. This work clarifies the turbulent boundary-layer development and loss characteristics of sCO2 in compressor cascades, establishing a foundation and a benchmark case for turbulence-model validation and future turbomachinery design in non-ideal compressible flow regimes. Comparative simulations with air are performed under matched inlet conditions (Mach number, Reynolds number, and inflow turbulence) to investigate the influence of non-ideal fluid properties on boundary layer development, flow separation, and aerodynamic losses. The results reveal that due to local high Reynolds number, sCO2 exhibits earlier transition and reattachment on the suction side, while air develops a wider separated region and stronger wake losses. This results in the sCO2 case exhibits a higher pressure ratio and greater average turning angles across the cascade when compared to air. The temperature variation, on the other hand, is smaller for sCO2 due to its higher Eckert number. Many findings from the turbulent boundary layer literature are confirmed in this paper. In addition, a liquid-like viscosity variation is observed within the sCO2 boundary layers, consistent with dense-vapor behavior reported in previous studies. The inner-layer scaling of the turbulent boundary layer is also verified in the cascade configuration.