Roles of Reynolds Number and Incidence Angle in the Competitive Interaction of Corner and Mid-Span Separations in a Low-Reynolds-Number Compressor Cascade

Abstract Corner separation and mid-span separation are inherently unsteady flow phenomena that significantly impair compressor performance under high-altitude, low-Reynolds-number (Re) conditions. Their dynamic interaction remains inadequately understood. This study employs Large Eddy Simulation (LES) to investigate the interplay between corner separation and mid-span laminar separation bubble (LSB) in a linear compressor cascade (Ma = 0.66) under low-Re conditions, with a focus on the coupled effects of incidence angle and Re. Results show that total loss increases at both −4° and +4° incidence compared to the design condition, driven predominantly by pressure-side profile loss and augmented corner separation loss, respectively. A critical Reynolds number governing flow regime transition are identified. This Critical Re (between 2.0×105 and 2.5×105) marks the onset of a competitive interaction between the mid-span and corner separations. Below this threshold, the cross-flow-mediated competition becomes dominant, leading to an accelerated redistribution of losses from the corner towards the mid-span and a fundamental shift in the evolution of the outlet flow angle. These findings, especially the identification of the Critical Re, provide new insights into aerodynamic design of compressors operating at high altitudes where low-Re effects are critical.