Control of Corner Separation for a Linear Compressor Cascade via Bionic Slanting Riblets at the Endwall

A new passive control approach, utilizing bionic slanting riblets, is employed to mitigate the flow close to the blade endwall in a linear cascade, and its effectiveness and mechanism in controlling corner separation are investigated through numerical simulations. The slanting riblets are positioned at the endwall upstream of the cascade channel, and the influence of riblet height, yaw angle and relative position on the control of corner separation is investigated. The findings indicate that the application of slanting riblets can efficiently counteract corner separation across the stable operational range. Specifically, the introduction of riblets with a height of merely 0.1 times the boundary layer thickness results in a significant reduction in total pressure loss by up to 14.53%, while simultaneously enhancing the static pressure coefficient by 21.74%. Flow analysis reveals that minute vortices produced within the riblet channels tend to coalesce, forming a potent large-scale vortex near the boundary layer’s base downstream. This phenomenon results in reduced additional losses compared to conventional vortex generators. Additionally, the induced vortex promotes enhanced mixing between the mainstream flow and boundary layer, inhibiting the lateral displacement of low-energy fluids within the endwall boundary layer. Consequently, this delays the onset of separation vortex formation and eliminates vortex rings in the corner region, ultimately enhancing the aerodynamic efficiency of the cascade.